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| author | Joe Hunkeler <jhunkeler@gmail.com> | 2015-08-11 16:51:37 -0400 |
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| committer | Joe Hunkeler <jhunkeler@gmail.com> | 2015-08-11 16:51:37 -0400 |
| commit | 40e5a5811c6ffce9b0974e93cdd927cbcf60c157 (patch) | |
| tree | 4464880c571602d54f6ae114729bf62a89518057 /vendor/cfitsio/cfitsio.doc | |
| download | iraf-osx-40e5a5811c6ffce9b0974e93cdd927cbcf60c157.tar.gz | |
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diff --git a/vendor/cfitsio/cfitsio.doc b/vendor/cfitsio/cfitsio.doc new file mode 100644 index 00000000..d22704bf --- /dev/null +++ b/vendor/cfitsio/cfitsio.doc @@ -0,0 +1,9535 @@ + CFITSIO - An Interface to FITS Format Files for C Programmers + + William D Pence, HEASARC, NASA/GSFC + Version 3.0 + + +[Note: This file contains various formatting command symbols ('*', '-') +in the first column which are used when generating the LATeX version of +this document.] + +*I. Introduction + +**A. A Brief Overview + +CFITSIO is a machine-independent library of routines for reading and +writing data files in the FITS (Flexible Image Transport System) data +format. It can also read IRAF format image files and raw binary data +arrays by converting them on the fly into a virtual FITS format file. +This library is written in ANSI C and provides a powerful yet simple +interface for accessing FITS files which will run on most commonly used +computers and workstations. CFITSIO supports all the features +described in the official NOST definition of the FITS format and can +read and write all the currently defined types of extensions, including +ASCII tables (TABLE), Binary tables (BINTABLE) and IMAGE extensions. +The CFITSIO routines insulate the programmer from having to deal with +the complicated formatting details in the FITS file, however, it is +assumed that users have a general knowledge about the structure and +usage of FITS files. + +CFITSIO also contains a set of Fortran callable wrapper routines which +allow Fortran programs to call the CFITSIO routines. See the companion +``FITSIO User's Guide'' for the definition of the Fortran subroutine +calling sequences. These wrappers replace the older Fortran FITSIO +library which is no longer supported. + +The CFITSIO package was initially developed by the HEASARC (High Energy +Astrophysics Science Archive Research Center) at the NASA Goddard Space +Flight Center to convert various existing and newly acquired +astronomical data sets into FITS format and to further analyze data +already in FITS format. New features continue to be added to CFITSIO +in large part due to contributions of ideas or actual code from +users of the package. The Integral Science Data Center in Switzerland, +and the XMM/ESTEC project in The Netherlands made especially significant +contributions that resulted in many of the new features that appeared +in v2.0 of CFITSIO. + +**B. Sources of FITS Software and Information + +The latest version of the CFITSIO source code, +documentation, and example programs are available on the World-Wide +Web or via anonymous ftp from: +- + http://heasarc.gsfc.nasa.gov/fitsio + ftp://legacy.gsfc.nasa.gov/software/fitsio/c +- + +Any questions, bug reports, or suggested enhancements related to the CFITSIO +package should be sent to the primary author: +- + Dr. William Pence Telephone: (301) 286-4599 + HEASARC, Code 662 E-mail: William.D.Pence@nasa.gov + NASA/Goddard Space Flight Center + Greenbelt, MD 20771, USA +- +This User's Guide assumes that readers already have a general +understanding of the definition and structure of FITS format files. +Further information about FITS formats is available from the FITS Support +Office at {\tt http://fits.gsfc.nasa.gov}. In particular, the +'NOST FITS Standard' gives the authoritative definition of the FITS data +format, and the `FITS User's Guide' provides additional historical background +and practical advice on using FITS files. + +The HEASARC also provides a very sophisticated FITS file analysis +program called `Fv' which can be used to display and edit the contents +of any FITS file as well as construct new FITS files from scratch. The +display functions in Fv allow users to interactively adjust the +brightness and contrast of images, pan, zoom, and blink images, and +measure the positions and brightnesses of objects within images. FITS +tables can be displayed like a spread sheet, and then modified using +powerful calculator and sorting functions. Fv is freely available for +most Unix platforms, Mac PCs, and Windows PCs. +CFITSIO users may also be interested in the FTOOLS package of programs +that can be used to manipulate and analyze FITS format files. +Fv and FTOOLS are available from their respective Web sites at: +- + http://fv.gsfc.nasa.gov + http://heasarc.gsfc.nasa.gov/ftools +- + +**C. Acknowledgments + +The development of the many powerful features in CFITSIO was made +possible through collaborations with many people or organizations from +around the world. The following in particular have made especially +significant contributions: + +Programmers from the Integral Science Data Center, Switzerland (namely, +Jurek Borkowski, Bruce O'Neel, and Don Jennings), designed the concept +for the plug-in I/O drivers that was introduced with CFITSIO 2.0. The +use of `drivers' greatly simplified the low-level I/O, which in turn +made other new features in CFITSIO (e.g., support for compressed FITS +files and support for IRAF format image files) much easier to +implement. Jurek Borkowski wrote the Shared Memory driver, and Bruce +O'Neel wrote the drivers for accessing FITS files over the network +using the FTP, HTTP, and ROOT protocols. Also, in 2009, Bruce O'Neel +was the key developer of the thread-safe version of CFITSIO. + +The ISDC also provided the template parsing routines (written by Jurek +Borkowski) and the hierarchical grouping routines (written by Don +Jennings). The ISDC DAL (Data Access Layer) routines are layered on +top of CFITSIO and make extensive use of these features. + +Giuliano Taffoni and Andrea Barisani, at INAF, University of Trieste, +Italy, implemented the I/O driver routines for accessing FITS files +on the computational grids using the gridftp protocol. + +Uwe Lammers (XMM/ESA/ESTEC, The Netherlands) designed the +high-performance lexical parsing algorithm that is used to do +on-the-fly filtering of FITS tables. This algorithm essentially +pre-compiles the user-supplied selection expression into a form that +can be rapidly evaluated for each row. Peter Wilson (RSTX, NASA/GSFC) +then wrote the parsing routines used by CFITSIO based on Lammers' +design, combined with other techniques such as the CFITSIO iterator +routine to further enhance the data processing throughput. This effort +also benefited from a much earlier lexical parsing routine that was +developed by Kent Blackburn (NASA/GSFC). More recently, Craig Markwardt +(NASA/GSFC) implemented additional functions (median, average, stddev) +and other enhancements to the lexical parser. + +The CFITSIO iterator function is loosely based on similar ideas +developed for the XMM Data Access Layer. + +Peter Wilson (RSTX, NASA/GSFC) wrote the complete set of +Fortran-callable wrappers for all the CFITSIO routines, which in turn +rely on the CFORTRAN macro developed by Burkhard Burow. + +The syntax used by CFITSIO for filtering or binning input FITS files is +based on ideas developed for the AXAF Science Center Data Model by +Jonathan McDowell, Antonella Fruscione, Aneta Siemiginowska and Bill +Joye. See http://heasarc.gsfc.nasa.gov/docs/journal/axaf7.html for +further description of the AXAF Data Model. + +The file decompression code were taken directly from the gzip (GNU zip) +program developed by Jean-loup Gailly and others. + +The new compressed image data format (where the image is tiled and +the compressed byte stream from each tile is stored in a binary table) +was implemented in collaboration with Richard White (STScI), Perry +Greenfield (STScI) and Doug Tody (NOAO). + +Doug Mink (SAO) provided the routines for converting IRAF format +images into FITS format. + +Martin Reinecke (Max Planck Institute, Garching)) provided the modifications to +cfortran.h that are necessary to support 64-bit integer values when calling +C routines from fortran programs. The cfortran.h macros were originally developed +by Burkhard Burow (CERN). + +Julian Taylor (ESO, Garching) provided the fast byte-swapping algorithms +that use the SSE2 and SSSE3 machine instructions available on x86\_64 CPUs. + +In addition, many other people have made valuable contributions to the +development of CFITSIO. These include (with apologies to others that may +have inadvertently been omitted): + +Steve Allen, Carl Akerlof, Keith Arnaud, Morten Krabbe Barfoed, Kent +Blackburn, G Bodammer, Romke Bontekoe, Lucio Chiappetti, Keith Costorf, +Robin Corbet, John Davis, Richard Fink, Ning Gan, Emily Greene, Gretchen +Green, Joe Harrington, Cheng Ho, Phil Hodge, Jim Ingham, Yoshitaka +Ishisaki, Diab Jerius, Mark Levine, Todd Karakaskian, Edward King, +Scott Koch, Claire Larkin, Rob Managan, Eric Mandel, Richard Mathar, +John Mattox, Carsten Meyer, Emi Miyata, Stefan Mochnacki, Mike Noble, +Oliver Oberdorf, Clive Page, Arvind Parmar, Jeff Pedelty, Tim Pearson, +Philippe Prugniel, Maren Purves, Scott Randall, Chris Rogers, Arnold Rots, +Rob Seaman, Barry Schlesinger, Robin Stebbins, Andrew Szymkowiak, Allyn Tennant, +Peter Teuben, James Theiler, Doug Tody, Shiro Ueno, Steve Walton, Archie +Warnock, Alan Watson, Dan Whipple, Wim Wimmers, Peter Young, Jianjun Xu, +and Nelson Zarate. + +**D. Legal Stuff + +Copyright (Unpublished--all rights reserved under the copyright laws of +the United States), U.S. Government as represented by the Administrator +of the National Aeronautics and Space Administration. No copyright is +claimed in the United States under Title 17, U.S. Code. + +Permission to freely use, copy, modify, and distribute this software +and its documentation without fee is hereby granted, provided that this +copyright notice and disclaimer of warranty appears in all copies. + +DISCLAIMER: + +THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, +EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, +ANY WARRANTY THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY +IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR +PURPOSE, AND FREEDOM FROM INFRINGEMENT, AND ANY WARRANTY THAT THE +DOCUMENTATION WILL CONFORM TO THE SOFTWARE, OR ANY WARRANTY THAT THE +SOFTWARE WILL BE ERROR FREE. IN NO EVENT SHALL NASA BE LIABLE FOR ANY +DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT, INDIRECT, SPECIAL OR +CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM, OR IN ANY WAY +CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY, +CONTRACT, TORT , OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY +PERSONS OR PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED +FROM, OR AROSE OUT OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR +SERVICES PROVIDED HEREUNDER." + +*II. Creating the CFITSIO Library + +**A. Building the Library + +The CFITSIO code is contained in about 40 C source files (*.c) and header +files (*.h). On VAX/VMS systems 2 assembly-code files (vmsieeed.mar and +vmsieeer.mar) are also needed. + +CFITSIO has currently been tested on the following platforms (not up-to-date): +- + OPERATING SYSTEM COMPILER + Sun OS gcc and cc (3.0.1) + Sun Solaris gcc and cc + Silicon Graphics IRIX gcc and cc + Silicon Graphics IRIX64 MIPS + Dec Alpha OSF/1 gcc and cc + DECstation Ultrix gcc + Dec Alpha OpenVMS cc + DEC VAX/VMS gcc and cc + HP-UX gcc + IBM AIX gcc + Linux gcc + MkLinux DR3 + Windows 95/98/NT Borland C++ V4.5 + Windows 95/98/NT/ME/XP Microsoft/Compaq Visual C++ v5.0, v6.0 + Windows 95/98/NT Cygwin gcc + MacOS 7.1 or greater Metrowerks 10.+ + MacOS-X 10.1 or greater cc (gcc) +- +CFITSIO will probably run on most other Unix platforms. Cray +supercomputers are currently not supported. + +***1. Unix Systems + +The CFITSIO library is built on Unix systems by typing: +- + > ./configure [--prefix=/target/installation/path] [--enable-reentrant] + [--enable-sse2] [--enable-ssse3] + > make (or 'make shared') + > make install (this step is optional) +- +at the operating system prompt. The configure command customizes the +Makefile for the particular system, then the `make' command compiles the +source files and builds the library. Type `./configure' and not simply +`configure' to ensure that the configure script in the current directory +is run and not some other system-wide configure script. The optional +'prefix' argument to configure gives the path to the directory where +the CFITSIO library and include files should be installed via the later +'make install' command. For example, +- + > ./configure --prefix=/usr1/local +- +will cause the 'make install' command to copy the CFITSIO libcfitsio file +to /usr1/local/lib and the necessary include files to /usr1/local/include +(assuming of course that the process has permission to write to these +directories). + +The optional --enable-reentrant flag will attempt to configure CFITSIO +so that it can be used in multi-threaded programs. See the "Using CFITSIO in Multi-threaded Environments" section, below, for more details. + +The optional --enable-sse2 and --enable-ssse3 flags will cause configure to +attempt to build CFITSIO using faster byte-swapping algorithms. +See the "Optimizing Programs" chapter of this manual for +more information about these options. + +The 'make shared' option builds a shared or dynamic version of the +CFITSIO library. When using the shared library the executable code is +not copied into your program at link time and instead the program +locates the necessary library code at run time, normally through +LD\_LIBRARY\_PATH or some other method. The advantages of using a shared +library are: +- + 1. Less disk space if you build more than 1 program + 2. Less memory if more than one copy of a program using the shared + library is running at the same time since the system is smart + enough to share copies of the shared library at run time. + 3. Possibly easier maintenance since a new version of the shared + library can be installed without relinking all the software + that uses it (as long as the subroutine names and calling + sequences remain unchanged). + 4. No run-time penalty. +- +The disadvantages are: +- + 1. More hassle at runtime. You have to either build the programs + specially or have LD_LIBRARY_PATH set right. + 2. There may be a slight start up penalty, depending on where you are + reading the shared library and the program from and if your CPU is + either really slow or really heavily loaded. +- + +On Mac OS X platforms the 'make shared' command works like on other +UNIX platforms, but a .dylib file will be created instead of .so. If +installed in a nonstandard location, add its location to the +DYLD\_LIBRARY\_PATH environment variable so that the library can be found +at run time. + +On HP/UX systems, the environment variable CFLAGS should be set +to -Ae before running configure to enable "extended ANSI" features. + +By default, a set of Fortran-callable wrapper routines are +also built and included in the CFITSIO library. If these wrapper +routines are not needed (i.e., the CFITSIO library will not +be linked to any Fortran applications which call FITSIO subroutines) +then they may be omitted from the build by typing 'make all-nofitsio' +instead of simply typing 'make'. This will reduce the size +of the CFITSIO library slightly. + +It may not be possible to statically link programs that use CFITSIO on +some platforms (namely, on Solaris 2.6) due to the network drivers +(which provide FTP and HTTP access to FITS files). It is possible to +make both a dynamic and a static version of the CFITSIO library, but +network file access will not be possible using the static version. + +***2. VMS + +On VAX/VMS and ALPHA/VMS systems the make\_gfloat.com command file may +be executed to build the cfitsio.olb object library using the default +G-floating point option for double variables. The make\_dfloat.com and +make\_ieee.com files may be used instead to build the library with the +other floating point options. Note that the getcwd function that is +used in the group.c module may require that programs using CFITSIO be +linked with the ALPHA\$LIBRARY:VAXCRTL.OLB library. See the example +link line in the next section of this document. + +***3. Windows PCs + +A precompiled DLL version of CFITSIO is available for IBM-PC users of +the Borland or Microsoft Visual C++ compilers in the files +cfitsiodll\_3xxx\_borland.zip and cfitsiodll\_3xxx\_vcc.zip, where +'3xxx' represents the current release number. These zip archives also +contains other files and instructions on how to use the CFITSIO DLL +library. + +The CFITSIO library may also be built from the source code using the +makefile.bc or makefile.vcc files. Finally, the makepc.bat file gives +an example of building CFITSIO with the Borland C++ v4.5 or v5.5 compiler +using older DOS commands. + +***4. Macintosh PCs + +When building on Mac OS-X, users should follow the Unix instructions, +above. See the README.MacOS file for instructions on building a Universal +Binary that supports both Intel and PowerPC CPUs. + +**B. Testing the Library + +The CFITSIO library should be tested by building and running +the testprog.c program that is included with the release. +On Unix systems, type: +- + % make testprog + % testprog > testprog.lis + % diff testprog.lis testprog.out + % cmp testprog.fit testprog.std +- + On VMS systems, +(assuming cc is the name of the C compiler command), type: +- + $ cc testprog.c + $ link testprog, cfitsio/lib, alpha$library:vaxcrtl/lib + $ run testprog +- +The test program should produce a FITS file called `testprog.fit' +that is identical to the `testprog.std' FITS file included with this +release. The diagnostic messages (which were piped to the file +testprog.lis in the Unix example) should be identical to the listing +contained in the file testprog.out. The 'diff' and 'cmp' commands +shown above should not report any differences in the files. (There +may be some minor format differences, such as the presence or +absence of leading zeros, or 3 digit exponents in numbers, +which can be ignored). + +The Fortran wrappers in CFITSIO may be tested with the testf77 +program on Unix systems with: +- + % f77 -o testf77 testf77.f -L. -lcfitsio -lnsl -lsocket + or + % f77 -f -o testf77 testf77.f -L. -lcfitsio (under SUN O/S) + or + % f77 -o testf77 testf77.f -Wl,-L. -lcfitsio -lm -lnsl -lsocket (HP/UX) + + % testf77 > testf77.lis + % diff testf77.lis testf77.out + % cmp testf77.fit testf77.std +- +On machines running SUN O/S, Fortran programs must be compiled with the +'-f' option to force double precision variables to be aligned on 8-byte +boundarys to make the fortran-declared variables compatible with C. A +similar compiler option may be required on other platforms. Failing to +use this option may cause the program to crash on FITSIO routines that +read or write double precision variables. + +Also note that on some systems, the output listing of the testf77 +program may differ slightly from the testf77.std template, if leading +zeros are not printed by default before the decimal point when using F +format. + +A few other utility programs are included with CFITSIO; the first four +of this programs can be compiled an linked by typing `make +program\_name' where `program\_name' is the actual name of the program: +- + speed - measures the maximum throughput (in MB per second) + for writing and reading FITS files with CFITSIO. + + listhead - lists all the header keywords in any FITS file + + fitscopy - copies any FITS file (especially useful in conjunction + with the CFITSIO's extended input filename syntax). + + cookbook - a sample program that performs common read and + write operations on a FITS file. + + iter_a, iter_b, iter_c - examples of the CFITSIO iterator routine +- + +**C. Linking Programs with CFITSIO + +When linking applications software with the CFITSIO library, several +system libraries usually need to be specified on the link command +line. On Unix systems, the most reliable way to determine what +libraries are required is to type 'make testprog' and see what +libraries the configure script has added. The typical libraries that +need to be added are -lm (the math library) and -lnsl and -lsocket +(needed only for FTP and HTTP file access). These latter 2 libraries +are not needed on VMS and Windows platforms, because FTP file access is +not currently supported on those platforms. + +Note that when upgrading to a newer version of CFITSIO it is usually +necessary to recompile, as well as relink, the programs that use CFITSIO, +because the definitions in fitsio.h often change. + +**D. Using CFITSIO in Multi-threaded Environments + +CFITSIO can be used either with the +POSIX pthreads interface or the OpenMP interface for multi-threaded +parallel programs. When used in a multi-threaded environment, +the CFITSIO library *must* be built using +the -D\_REENTRANT compiler directive. This can be done using the following +build commands: +- + >./configure --enable-reentrant + > make +- +A function called fits\_is\_reentrant is available to test +whether or not CFITSIO was compiled with the -D\_REENTRANT +directive. When this feature is enabled, multiple threads can +call any of the CFITSIO routines +to simultaneously read or write separate +FITS files. Multiple threads can also read data from +the same FITS file simultaneously, as long as the file +was opened independently by each thread. This relies on +the operating system to correctly deal with reading the +same file by multiple processes. Different threads should +not share the same 'fitsfile' pointer to read an opened +FITS file, unless locks are placed around the calls to +the CFITSIO reading routines. +Different threads should never try to write to the same +FITS file. + +**E. Getting Started with CFITSIO + +In order to effectively use the CFITSIO library it is recommended that +new users begin by reading the ``CFITSIO Quick Start Guide''. It +contains all the basic information needed to write programs that +perform most types of operations on FITS files. The set of example +FITS utility programs that are available from the CFITSIO web site are +also very useful for learning how to use CFITSIO. To learn even more +about the capabilities of the CFITSIO library the following steps are +recommended: + +1. Read the following short `FITS Primer' chapter for an overview of +the structure of FITS files. + +2. Review the Programming Guidelines in Chapter 4 to become familiar +with the conventions used by the CFITSIO interface. + +3. Refer to the cookbook.c, listhead.c, and fitscopy.c programs that +are included with this release for examples of routines that perform +various common FITS file operations. Type 'make program\_name' to +compile and link these programs on Unix systems. + +4. Write a simple program to read or write a FITS file using the Basic +Interface routines described in Chapter 5. + +5. Scan through the more specialized routines that are described in +the following chapters to become familiar with the functionality that +they provide. + +**F. Example Program + +The following listing shows an example of how to use the CFITSIO +routines in a C program. Refer to the cookbook.c program that is +included with the CFITSIO distribution for other example routines. + +This program creates a new FITS file, containing a FITS image. An +`EXPOSURE' keyword is written to the header, then the image data are +written to the FITS file before closing the FITS file. +- +#include "fitsio.h" /* required by every program that uses CFITSIO */ +main() +{ + fitsfile *fptr; /* pointer to the FITS file; defined in fitsio.h */ + int status, ii, jj; + long fpixel = 1, naxis = 2, nelements, exposure; + long naxes[2] = { 300, 200 }; /* image is 300 pixels wide by 200 rows */ + short array[200][300]; + + status = 0; /* initialize status before calling fitsio routines */ + fits_create_file(&fptr, "testfile.fits", &status); /* create new file */ + + /* Create the primary array image (16-bit short integer pixels */ + fits_create_img(fptr, SHORT_IMG, naxis, naxes, &status); + + /* Write a keyword; must pass the ADDRESS of the value */ + exposure = 1500.; + fits_update_key(fptr, TLONG, "EXPOSURE", &exposure, + "Total Exposure Time", &status); + + /* Initialize the values in the image with a linear ramp function */ + for (jj = 0; jj < naxes[1]; jj++) + for (ii = 0; ii < naxes[0]; ii++) + array[jj][ii] = ii + jj; + + nelements = naxes[0] * naxes[1]; /* number of pixels to write */ + + /* Write the array of integers to the image */ + fits_write_img(fptr, TSHORT, fpixel, nelements, array[0], &status); + + fits_close_file(fptr, &status); /* close the file */ + + fits_report_error(stderr, status); /* print out any error messages */ + return( status ); +} +- + +*III. A FITS Primer + +This section gives a brief overview of the structure of FITS files. +Users should refer to the documentation available from the NOST, as +described in the introduction, for more detailed information on FITS +formats. + +FITS was first developed in the late 1970's as a standard data +interchange format between various astronomical observatories. Since +then FITS has become the standard data format supported by most +astronomical data analysis software packages. + +A FITS file consists of one or more Header + Data Units (HDUs), where +the first HDU is called the `Primary HDU', or `Primary Array'. The +primary array contains an N-dimensional array of pixels, such as a 1-D +spectrum, a 2-D image, or a 3-D data cube. Six different primary +data types are supported: Unsigned 8-bit bytes, 16-bit, 32-bit, and 64-bit signed +integers, and 32 and 64-bit floating point reals. FITS also has a +convention for storing 16 and 32-bit unsigned integers (see the later +section entitled `Unsigned Integers' for more details). The primary HDU +may also consist of only a header with a null array containing no +data pixels. + +Any number of additional HDUs may follow the primary array; these +additional HDUs are called FITS `extensions'. There are currently 3 +types of extensions defined by the FITS standard: + +\begin{itemize} +\item + Image Extension - a N-dimensional array of pixels, like in a primary array +\item + ASCII Table Extension - rows and columns of data in ASCII character format +\item + Binary Table Extension - rows and columns of data in binary representation +\end{itemize} + +In each case the HDU consists of an ASCII Header Unit followed by an optional +Data Unit. For historical reasons, each Header or Data unit must be an +exact multiple of 2880 8-bit bytes long. Any unused space is padded +with fill characters (ASCII blanks or zeros). + +Each Header Unit consists of any number of 80-character keyword records +or `card images' which have the +general form: +- + KEYNAME = value / comment string + NULLKEY = / comment: This keyword has no value +- +The keyword names may be up to 8 characters long and can only contain +uppercase letters, the digits 0-9, the hyphen, and the underscore +character. The keyword name is (usually) followed by an equals sign and +a space character (= ) in columns 9 - 10 of the record, followed by the +value of the keyword which may be either an integer, a floating point +number, a character string (enclosed in single quotes), or a boolean +value (the letter T or F). A keyword may also have a null or undefined +value if there is no specified value string, as in the second example, above + +The last keyword in the header is always the `END' keyword which has no +value or comment fields. There are many rules governing the exact +format of a keyword record (see the NOST FITS Standard) so it is better +to rely on standard interface software like CFITSIO to correctly +construct or to parse the keyword records rather than try to deal +directly with the raw FITS formats. + +Each Header Unit begins with a series of required keywords which depend +on the type of HDU. These required keywords specify the size and +format of the following Data Unit. The header may contain other +optional keywords to describe other aspects of the data, such as the +units or scaling values. Other COMMENT or HISTORY keywords are also +frequently added to further document the data file. + +The optional Data Unit immediately follows the last 2880-byte block in +the Header Unit. Some HDUs do not have a Data Unit and only consist of +the Header Unit. + +If there is more than one HDU in the FITS file, then the Header Unit of +the next HDU immediately follows the last 2880-byte block of the +previous Data Unit (or Header Unit if there is no Data Unit). + +The main required keywords in FITS primary arrays or image extensions are: +\begin{itemize} +\item +BITPIX -- defines the data type of the array: 8, 16, 32, 64, -32, -64 for +unsigned 8--bit byte, 16--bit signed integer, 32--bit signed integer, +32--bit IEEE floating point, and 64--bit IEEE double precision floating +point, respectively. +\item +NAXIS -- the number of dimensions in the array, usually 0, 1, 2, 3, or 4. +\item +NAXISn -- (n ranges from 1 to NAXIS) defines the size of each dimension. +\end{itemize} + +FITS tables start with the keyword XTENSION = `TABLE' (for ASCII +tables) or XTENSION = `BINTABLE' (for binary tables) and have the +following main keywords: +\begin{itemize} +\item +TFIELDS -- number of fields or columns in the table +\item +NAXIS2 -- number of rows in the table +\item +TTYPEn -- for each column (n ranges from 1 to TFIELDS) gives the +name of the column +\item +TFORMn -- the data type of the column +\item +TUNITn -- the physical units of the column (optional) +\end{itemize} + +Users should refer to the FITS Support Office at {\tt http://fits.gsfc.nasa.gov} +for further information about the FITS format and related software +packages. + + +*IV. Programming Guidelines + +**A. CFITSIO Definitions + +Any program that uses the CFITSIO interface must include the fitsio.h +header file with the statement +- + #include "fitsio.h" +- +This header file contains the prototypes for all the CFITSIO user +interface routines as well as the definitions of various constants used +in the interface. It also defines a C structure of type `fitsfile' +that is used by CFITSIO to store the relevant parameters that define +the format of a particular FITS file. Application programs must define +a pointer to this structure for each FITS file that is to be opened. +This structure is initialized (i.e., memory is allocated for the +structure) when the FITS file is first opened or created with the +fits\_open\_file or fits\_create\_file routines. This fitsfile pointer +is then passed as the first argument to every other CFITSIO routine +that operates on the FITS file. Application programs must not directly +read or write elements in this fitsfile structure because the +definition of the structure may change in future versions of CFITSIO. + +A number of symbolic constants are also defined in fitsio.h for the +convenience of application programmers. Use of these symbolic +constants rather than the actual numeric value will help to make the +source code more readable and easier for others to understand. +- +String Lengths, for use when allocating character arrays: + + #define FLEN_FILENAME 1025 /* max length of a filename */ + #define FLEN_KEYWORD 72 /* max length of a keyword */ + #define FLEN_CARD 81 /* max length of a FITS header card */ + #define FLEN_VALUE 71 /* max length of a keyword value string */ + #define FLEN_COMMENT 73 /* max length of a keyword comment string */ + #define FLEN_ERRMSG 81 /* max length of a CFITSIO error message */ + #define FLEN_STATUS 31 /* max length of a CFITSIO status text string */ + + Note that FLEN_KEYWORD is longer than the nominal 8-character keyword + name length because the HIERARCH convention supports longer keyword names. + +Access modes when opening a FITS file: + + #define READONLY 0 + #define READWRITE 1 + +BITPIX data type code values for FITS images: + + #define BYTE_IMG 8 /* 8-bit unsigned integers */ + #define SHORT_IMG 16 /* 16-bit signed integers */ + #define LONG_IMG 32 /* 32-bit signed integers */ + #define LONGLONG_IMG 64 /* 64-bit signed integers */ + #define FLOAT_IMG -32 /* 32-bit single precision floating point */ + #define DOUBLE_IMG -64 /* 64-bit double precision floating point */ + + The following 4 data type codes are also supported by CFITSIO: + #define SBYTE_IMG 10 /* 8-bit signed integers, equivalent to */ + /* BITPIX = 8, BSCALE = 1, BZERO = -128 */ + #define USHORT_IMG 20 /* 16-bit unsigned integers, equivalent to */ + /* BITPIX = 16, BSCALE = 1, BZERO = 32768 */ + #define ULONG_IMG 40 /* 32-bit unsigned integers, equivalent to */ + /* BITPIX = 32, BSCALE = 1, BZERO = 2147483648 */ + +Codes for the data type of binary table columns and/or for the +data type of variables when reading or writing keywords or data: + + DATATYPE TFORM CODE + #define TBIT 1 /* 'X' */ + #define TBYTE 11 /* 8-bit unsigned byte, 'B' */ + #define TLOGICAL 14 /* logicals (int for keywords */ + /* and char for table cols 'L' */ + #define TSTRING 16 /* ASCII string, 'A' */ + #define TSHORT 21 /* signed short, 'I' */ + #define TLONG 41 /* signed long, */ + #define TLONGLONG 81 /* 64-bit long signed integer 'K' */ + #define TFLOAT 42 /* single precision float, 'E' */ + #define TDOUBLE 82 /* double precision float, 'D' */ + #define TCOMPLEX 83 /* complex (pair of floats) 'C' */ + #define TDBLCOMPLEX 163 /* double complex (2 doubles) 'M' */ + + The following data type codes are also supported by CFITSIO: + #define TINT 31 /* int */ + #define TSBYTE 12 /* 8-bit signed byte, 'S' */ + #define TUINT 30 /* unsigned int 'V' */ + #define TUSHORT 20 /* unsigned short 'U' */ + #define TULONG 40 /* unsigned long */ + + The following data type code is only for use with fits\_get\_coltype + #define TINT32BIT 41 /* signed 32-bit int, 'J' */ + + +HDU type code values (value returned when moving to new HDU): + + #define IMAGE_HDU 0 /* Primary Array or IMAGE HDU */ + #define ASCII_TBL 1 /* ASCII table HDU */ + #define BINARY_TBL 2 /* Binary table HDU */ + #define ANY_HDU -1 /* matches any type of HDU */ + +Column name and string matching case-sensitivity: + + #define CASESEN 1 /* do case-sensitive string match */ + #define CASEINSEN 0 /* do case-insensitive string match */ + +Logical states (if TRUE and FALSE are not already defined): + + #define TRUE 1 + #define FALSE 0 + +Values to represent undefined floating point numbers: + + #define FLOATNULLVALUE -9.11912E-36F + #define DOUBLENULLVALUE -9.1191291391491E-36 + +Image compression algorithm definitions + + #define RICE_1 11 + #define GZIP_1 21 + #define PLIO_1 31 + #define HCOMPRESS_1 41 +- + +**B. Current Header Data Unit (CHDU) + +The concept of the Current Header and Data Unit, or CHDU, is +fundamental to the use of the CFITSIO library. A simple FITS image may +only contain a single Header and Data unit (HDU), but in general FITS +files can contain multiple Header Data Units (also known as +`extensions'), concatenated one after the other in the file. The user +can specify which HDU should be initially opened at run time by giving +the HDU name or number after the root file name. For example, +'myfile.fits[4]' opens the 5th HDU in the file (note that the numbering +starts with 0), and 'myfile.fits[EVENTS] opens the HDU with the name +'EVENTS' (as defined by the EXTNAME or HDUNAME keywords). If no HDU is +specified then CFITSIO opens the first HDU (the primary array) by +default. The CFITSIO routines which read and write data only operate +within the opened HDU, Other CFITSIO routines are provided to move to +and open any other existing HDU within the FITS file or to append or +insert new HDUs in the FITS file. + +**C. Function Names and Variable Datatypes + +Most of the CFITSIO routines have both a short name as well as a +longer descriptive name. The short name is only 5 or 6 characters long +and is similar to the subroutine name in the Fortran-77 version of +FITSIO. The longer name is more descriptive and it is recommended that +it be used instead of the short name to more clearly document the +source code. + +Many of the CFITSIO routines come in families which differ only in the +data type of the associated parameter(s). The data type of these +routines is indicated by the suffix of the routine name. The short +routine names have a 1 or 2 character suffix (e.g., 'j' in 'ffpkyj') +while the long routine names have a 4 character or longer suffix +as shown in the following table: +- + Long Short Data + Names Names Type + ----- ----- ---- + _bit x bit + _byt b unsigned byte + _sbyt sb signed byte + _sht i short integer + _lng j long integer + _lnglng jj 8-byte LONGLONG integer (see note below) + _usht ui unsigned short integer + _ulng uj unsigned long integer + _uint uk unsigned int integer + _int k int integer + _flt e real exponential floating point (float) + _fixflt f real fixed-decimal format floating point (float) + _dbl d double precision real floating-point (double) + _fixdbl g double precision fixed-format floating point (double) + _cmp c complex reals (pairs of float values) + _fixcmp fc complex reals, fixed-format floating point + _dblcmp m double precision complex (pairs of double values) + _fixdblcmp fm double precision complex, fixed-format floating point + _log l logical (int) + _str s character string +- + +The logical data type corresponds to `int' for logical keyword values, +and `byte' for logical binary table columns. In other words, the value +when writing a logical keyword must be stored in an `int' variable, and +must be stored in a `char' array when reading or writing to `L' columns +in a binary table. Implicit data type conversion is not supported for +logical table columns, but is for keywords, so a logical keyword may be +read and cast to any numerical data type; a returned value = 0 +indicates false, and any other value = true. + +The `int' data type may be 2 bytes long on some old PC compilers, +but otherwise it is nearly always 4 bytes long. Some 64-bit +machines, like the Alpha/OSF, define the `short', `int', +and `long' integer data types to be 2, 4, and 8 bytes long, +respectively. + +Because there is no universal C compiler standard for the name of the +8-byte integer datatype, the fitsio.h include file typedef's +'LONGLONG' to be equivalent to an +appropriate 8-byte integer data type on each supported platform. +For maximum software portability it is recommended that +this LONGLONG datatype be used to define 8-byte integer variables +rather than using the native data type name on a particular +platform. On most +32-bit Unix and Mac OS-X operating systems LONGLONG is equivalent to the +intrinsic 'long long' 8-byte integer datatype. On 64-bit systems (which currently +includes Alpha OSF/1, 64-bit Sun Solaris, 64-bit SGI MIPS, and 64-bit +Itanium and Opteron PC systems), LONGLONG is simply typedef'ed to be +equivalent to 'long'. Microsoft Visual C++ Version 6.0 does not define +a 'long long' data type, so LONGLONG is typedef'ed to be equivalent to +the '\_\_int64' data type on 32-bit windows systems when using Visual C++. + +A related issue that affects the portability of software is how to print +out the value of a 'LONGLONG' variable with printf. Developers may +find it convenient to use the following preprocessing statements +in their C programs to handle this in a machine-portable manner: + +- +#if defined(_MSC_VER) /* Microsoft Visual C++ */ + printf("%I64d", longlongvalue); + +#elif (USE_LL_SUFFIX == 1) + printf("%lld", longlongvalue); + +#else + printf("%ld", longlongvalue); +#endif +- + +Similarly, the name of the C utility routine that converts a character +string of digits into a 8-byte integer value is platform dependent: + +- +#if defined(_MSC_VER) /* Microsoft Visual C++ */ + /* VC++ 6.0 does not seem to have an 8-byte conversion routine */ + +#elif (USE_LL_SUFFIX == 1) + longlongvalue = atoll(*string); + +#else + longlongvalue = atol(*string); +#endif +- + +When dealing with the FITS byte data type it is important to remember +that the raw values (before any scaling by the BSCALE and BZERO, or +TSCALn and TZEROn keyword values) in byte arrays (BITPIX = 8) or byte +columns (TFORMn = 'B') are interpreted as unsigned bytes with values +ranging from 0 to 255. Some C compilers define a 'char' variable as +signed, so it is important to explicitly declare a numeric char +variable as 'unsigned char' to avoid any ambiguity + +One feature of the CFITSIO routines is that they can operate on a `X' +(bit) column in a binary table as though it were a `B' (byte) column. +For example a `11X' data type column can be interpreted the same as a +`2B' column (i.e., 2 unsigned 8-bit bytes). In some instances, it can +be more efficient to read and write whole bytes at a time, rather than +reading or writing each individual bit. + +The complex and double precision complex data types are not directly +supported in ANSI C so these data types should be interpreted as pairs +of float or double values, respectively, where the first value in each +pair is the real part, and the second is the imaginary part. + +**D. Support for Unsigned Integers and Signed Bytes + +Although FITS does not directly support unsigned integers as one of its +fundamental data types, FITS can still be used to efficiently store +unsigned integer data values in images and binary tables. The +convention used in FITS files is to store the unsigned integers as +signed integers with an associated offset (specified by the BZERO or +TZEROn keyword). For example, to store unsigned 16-bit integer values +in a FITS image the image would be defined as a signed 16-bit integer +(with BITPIX keyword = SHORT\_IMG = 16) with the keywords BSCALE = 1.0 +and BZERO = 32768. Thus the unsigned values of 0, 32768, and 65535, +for example, are physically stored in the FITS image as -32768, 0, and +32767, respectively; CFITSIO automatically adds the BZERO offset to +these values when they are read. Similarly, in the case of unsigned +32-bit integers the BITPIX keyword would be equal to LONG\_IMG = 32 and +BZERO would be equal to 2147483648 (i.e. 2 raised to the 31st power). + +The CFITSIO interface routines will efficiently and transparently apply +the appropriate offset in these cases so in general application +programs do not need to be concerned with how the unsigned values are +actually stored in the FITS file. As a convenience for users, CFITSIO +has several predefined constants for the value of BITPIX (USHORT\_IMG, +ULONG\_IMG) and for the TFORMn value in the case of binary tables (`U' +and `V') which programmers can use when creating FITS files containing +unsigned integer values. The following code fragment illustrates how +to write a FITS 1-D primary array of unsigned 16-bit integers: +- + unsigned short uarray[100]; + int naxis, status; + long naxes[10], group, firstelem, nelements; + ... + status = 0; + naxis = 1; + naxes[0] = 100; + fits_create_img(fptr, USHORT_IMG, naxis, naxes, &status); + + firstelem = 1; + nelements = 100; + fits_write_img(fptr, TUSHORT, firstelem, nelements, + uarray, &status); + ... +- +In the above example, the 2nd parameter in fits\_create\_img tells +CFITSIO to write the header keywords appropriate for an array of 16-bit +unsigned integers (i.e., BITPIX = 16 and BZERO = 32768). Then the +fits\_write\_img routine writes the array of unsigned short integers +(uarray) into the primary array of the FITS file. Similarly, a 32-bit +unsigned integer image may be created by setting the second parameter +in fits\_create\_img equal to `ULONG\_IMG' and by calling the +fits\_write\_img routine with the second parameter = TULONG to write +the array of unsigned long image pixel values. + +An analogous set of routines are available for reading or writing unsigned +integer values and signed byte values in a FITS binary table extension. +When specifying the TFORMn keyword value which defines the format of a +column, CFITSIO recognized 3 additional data type codes besides those +already defined in the FITS standard: `U' meaning a 16-bit unsigned +integer column, `V' for a 32-bit unsigned integer column, and 'S' +for a signed byte column. These non-standard data type codes are not +actually written into the FITS file but instead are just used internally +within CFITSIO. The following code fragment illustrates how to use +these features: +- + unsigned short uarray[100]; + unsigned int varray[100]; + + int colnum, tfields, status; + long nrows, firstrow, firstelem, nelements, pcount; + + char extname[] = "Test_table"; /* extension name */ + + /* define the name, data type, and physical units for the 2 columns */ + char *ttype[] = { "Col_1", "Col_2", "Col_3" }; + char *tform[] = { "1U", "1V", "1S"}; /* special CFITSIO codes */ + char *tunit[] = { " ", " ", " " }; + ... + + /* write the header keywords */ + status = 0; + nrows = 1; + tfields = 3 + pcount = 0; + fits_create_tbl(fptr, BINARY_TBL, nrows, tfields, ttype, tform, + tunit, extname, &status); + + /* write the unsigned shorts to the 1st column */ + colnum = 1; + firstrow = 1; + firstelem = 1; + nelements = 100; + fits_write_col(fptr, TUSHORT, colnum, firstrow, firstelem, + nelements, uarray, &status); + + /* now write the unsigned longs to the 2nd column */ + colnum = 2; + fits_write_col(fptr, TUINT, colnum, firstrow, firstelem, + nelements, varray, &status); + ... +- +Note that the non-standard TFORM values for the 3 columns, `U' and `V', +tell CFITSIO to write the keywords appropriate for unsigned 16-bit and +unsigned 32-bit integers, respectively (i.e., TFORMn = '1I' and TZEROn += 32678 for unsigned 16-bit integers, and TFORMn = '1J' and TZEROn = +2147483648 for unsigned 32-bit integers). The 'S' TFORMn value tells +CFITSIO to write the keywords appropriate for a signed 8-bit byte column +with TFORMn = '1B' and TZEROn = -128. The calls to fits\_write\_col +then write the arrays of unsigned integer values to the columns. + +**E. Dealing with Character Strings + +The character string values in a FITS header or in an ASCII column in a +FITS table extension are generally padded out with non-significant +space characters (ASCII 32) to fill up the header record or the column +width. When reading a FITS string value, the CFITSIO routines will +strip off these non-significant trailing spaces and will return a +null-terminated string value containing only the significant +characters. Leading spaces in a FITS string are considered +significant. If the string contains all blanks, then CFITSIO will +return a single blank character, i.e, the first blank is considered to +be significant, since it distinguishes the string from a null or +undefined string, but the remaining trailing spaces are not +significant. + +Similarly, when writing string values to a FITS file the +CFITSIO routines expect to get a null-terminated string as input; +CFITSIO will pad the string with blanks if necessary when writing it +to the FITS file. + +When calling CFITSIO routines that return a character string it is +vital that the size of the char array be large enough to hold the +entire string of characters, otherwise CFITSIO will overwrite whatever +memory locations follow the char array, possibly causing the program to +execute incorrectly. This type of error can be difficult to debug, so +programmers should always ensure that the char arrays are allocated +enough space to hold the longest possible string, {\bf including} the +terminating NULL character. The fitsio.h file contains the following +defined constants which programmers are strongly encouraged to use +whenever they are allocating space for char arrays: +- +#define FLEN_FILENAME 1025 /* max length of a filename */ +#define FLEN_KEYWORD 72 /* max length of a keyword */ +#define FLEN_CARD 81 /* length of a FITS header card */ +#define FLEN_VALUE 71 /* max length of a keyword value string */ +#define FLEN_COMMENT 73 /* max length of a keyword comment string */ +#define FLEN_ERRMSG 81 /* max length of a CFITSIO error message */ +#define FLEN_STATUS 31 /* max length of a CFITSIO status text string */ +- +For example, when declaring a char array to hold the value string +of FITS keyword, use the following statement: +- + char value[FLEN_VALUE]; +- +Note that FLEN\_KEYWORD is longer than needed for the nominal 8-character +keyword name because the HIERARCH convention supports longer keyword names. + +**F. Implicit Data Type Conversion + +The CFITSIO routines that read and write numerical data can perform +implicit data type conversion. This means that the data type of the +variable or array in the program does not need to be the same as the +data type of the value in the FITS file. Data type conversion is +supported for numerical and string data types (if the string contains a +valid number enclosed in quotes) when reading a FITS header keyword +value and for numeric values when reading or writing values in the +primary array or a table column. CFITSIO returns status = +NUM\_OVERFLOW if the converted data value exceeds the range of the +output data type. Implicit data type conversion is not supported +within binary tables for string, logical, complex, or double complex +data types. + +In addition, any table column may be read as if it contained string values. +In the case of numeric columns the returned string will be formatted +using the TDISPn display format if it exists. + +**G. Data Scaling + +When reading numerical data values in the primary array or a +table column, the values will be scaled automatically by the BSCALE and +BZERO (or TSCALn and TZEROn) header values if they are +present in the header. The scaled data that is returned to the reading +program will have +- + output value = (FITS value) * BSCALE + BZERO +- +(a corresponding formula using TSCALn and TZEROn is used when reading +from table columns). In the case of integer output values the floating +point scaled value is truncated to an integer (not rounded to the +nearest integer). The fits\_set\_bscale and fits\_set\_tscale routines +(described in the `Advanced' chapter) may be used to override the +scaling parameters defined in the header (e.g., to turn off the scaling +so that the program can read the raw unscaled values from the FITS +file). + +When writing numerical data to the primary array or to a table column +the data values will generally be automatically inversely scaled by the +value of the BSCALE and BZERO (or TSCALn and TZEROn) keyword values if +they they exist in the header. These keywords must have been written +to the header before any data is written for them to have any immediate +effect. One may also use the fits\_set\_bscale and fits\_set\_tscale +routines to define or override the scaling keywords in the header +(e.g., to turn off the scaling so that the program can write the raw +unscaled values into the FITS file). If scaling is performed, the +inverse scaled output value that is written into the FITS file will +have +- + FITS value = ((input value) - BZERO) / BSCALE +- +(a corresponding formula using TSCALn and TZEROn is used when +writing to table columns). Rounding to the nearest integer, rather +than truncation, is performed when writing integer data types to the +FITS file. + +**H. Support for IEEE Special Values + +The ANSI/IEEE-754 floating-point number standard defines certain +special values that are used to represent such quantities as +Not-a-Number (NaN), denormalized, underflow, overflow, and infinity. +(See the Appendix in the NOST FITS standard or the NOST FITS User's +Guide for a list of these values). The CFITSIO routines that read +floating point data in FITS files recognize these IEEE special values +and by default interpret the overflow and infinity values as being +equivalent to a NaN, and convert the underflow and denormalized values +into zeros. In some cases programmers may want access to the raw IEEE +values, without any modification by CFITSIO. This can be done by +calling the fits\_read\_img or fits\_read\_col routines while +specifying 0.0 as the value of the NULLVAL parameter. This will force +CFITSIO to simply pass the IEEE values through to the application +program without any modification. This is not fully supported on +VAX/VMS machines, however, where there is no easy way to bypass the +default interpretation of the IEEE special values. This is also not +supported when reading floating-point images that have been compressed +with the FITS tiled image compression convention that is discussed in +section 5.6; the pixels values in tile compressed images are +represented by scaled integers, and a reserved integer value +(not a NaN) is used to represent undefined pixels. + +**I. Error Status Values and the Error Message Stack + +Nearly all the CFITSIO routines return an error status value +in 2 ways: as the value of the last parameter in the function call, +and as the returned value of the function itself. This provides +some flexibility in the way programmers can test if an error +occurred, as illustrated in the following 2 code fragments: +- + if ( fits_write_record(fptr, card, &status) ) + printf(" Error occurred while writing keyword."); + +or, + + fits_write_record(fptr, card, &status); + if ( status ) + printf(" Error occurred while writing keyword."); +- +A listing of all the CFITSIO status code values is given at the end of +this document. Programmers are encouraged to use the symbolic +mnemonics (defined in fitsio.h) rather than the actual integer status +values to improve the readability of their code. + +The CFITSIO library uses an `inherited status' convention for the +status parameter which means that if a routine is called with a +positive input value of the status parameter as input, then the routine +will exit immediately without changing the value of the status +parameter. Thus, if one passes the status value returned from each +CFITSIO routine as input to the next CFITSIO routine, then whenever an +error is detected all further CFITSIO processing will cease. This +convention can simplify the error checking in application programs +because it is not necessary to check the value of the status parameter +after every single CFITSIO routine call. If a program contains a +sequence of several CFITSIO calls, one can just check the status value +after the last call. Since the returned status values are generally +distinctive, it should be possible to determine which routine +originally returned the error status. + +CFITSIO also maintains an internal stack of error messages +(80-character maximum length) which in many cases provide a more +detailed explanation of the cause of the error than is provided by the +error status number alone. It is recommended that the error message +stack be printed out whenever a program detects a CFITSIO error. The +function fits\_report\_error will print out the entire error message +stack, or alternatively one may call fits\_read\_errmsg to get the +error messages one at a time. + +**J. Variable-Length Arrays in Binary Tables + +CFITSIO provides easy-to-use support for reading and writing data in +variable length fields of a binary table. The variable length columns +have TFORMn keyword values of the form `1Pt(len)' where `t' is the +data type code (e.g., I, J, E, D, etc.) and `len' is an integer +specifying the maximum length of the vector in the table. (CFITSIO also +supports the experimental 'Q' datatype, which is identical to the 'P' type +except that is supports is a 64-bit address space and hence much larger +data structures). If the value +of `len' is not specified when the table is created (e.g., if the TFORM +keyword value is simply specified as '1PE' instead of '1PE(400) ), then +CFITSIO will automatically scan the table when it is closed to +determine the maximum length of the vector and will append this value +to the TFORMn value. + +The same routines that read and write data in an ordinary fixed length +binary table extension are also used for variable length fields, +however, the routine parameters take on a slightly different +interpretation as described below. + +All the data in a variable length field is written into an area called +the `heap' which follows the main fixed-length FITS binary table. The +size of the heap, in bytes, is specified by the PCOUNT keyword in the +FITS header. When creating a new binary table, the initial value of +PCOUNT should usually be set to zero. CFITSIO will recompute the size +of the heap as the data is written and will automatically update the +PCOUNT keyword value when the table is closed. When writing variable +length data to a table, CFITSIO will automatically extend the size +of the heap area if necessary, so that any following HDUs do not +get overwritten. + +By default the heap data area starts immediately after the last row of +the fixed-length table. This default starting location may be +overridden by the THEAP keyword, but this is not recommended. +If additional rows of data are added to the table, CFITSIO will +automatically shift the the heap down to make room for the new +rows, but it is obviously be more efficient to initially +create the table with the necessary number of blank rows, so that +the heap does not needed to be constantly moved. + +When writing row of data to a variable length field the entire array of values for +a given row of the table must be written with a single call to +fits\_write\_col. +The total length of the array is given by nelements ++ firstelem - 1. Additional elements cannot be appended to an existing +vector at a later time since any attempt to do so will simply overwrite +all the previously written data and the new data will be +written to a new area of the heap. The fits\_compress\_heap routine +is provided to compress the heap and recover any unused space. +To avoid having to deal with this issue, it is recommended +that rows in a variable length field should only be written once. +An exception to +this general rule occurs when setting elements of an array as +undefined. It is allowed to first write a dummy value into the array with +fits\_write\_col, and then call fits\_write\_col\_nul to flag the +desired elements as undefined. Note that the rows of a table, +whether fixed or variable length, do not have to be written +consecutively and may be written in any order. + +When writing to a variable length ASCII character field (e.g., TFORM = +'1PA') only a single character string can be written. The `firstelem' +and `nelements' parameter values in the fits\_write\_col routine are +ignored and the number of characters to write is simply determined by +the length of the input null-terminated character string. + +The fits\_write\_descript routine is useful in situations where +multiple rows of a variable length column have the identical array of +values. One can simply write the array once for the first row, and +then use fits\_write\_descript to write the same descriptor values into +the other rows; all the rows will then point to the same storage +location thus saving disk space. + +When reading from a variable length array field one can only read as +many elements as actually exist in that row of the table; reading does +not automatically continue with the next row of the table as occurs +when reading an ordinary fixed length table field. Attempts to read +more than this will cause an error status to be returned. One can +determine the number of elements in each row of a variable column with +the fits\_read\_descript routine. + +**K. Multiple Access to the Same FITS File + +CFITSIO supports simultaneous read and write access to multiple HDUs in +the same FITS file. Thus, one can open the same FITS file twice within +a single program and move to 2 different HDUs in the file, and then +read and write data or keywords to the 2 extensions just as if one were +accessing 2 completely separate FITS files. Since in general it is +not possible to physically open the same file twice and then expect to +be able to simultaneously (or in alternating succession) write to 2 +different locations in the file, CFITSIO recognizes when the file to be +opened (in the call to fits\_open\_file) has already been opened and +instead of actually opening the file again, just logically links the +new file to the old file. (This of course does not prevent the same +file from being simultaneously opened by more than one program). Then +before CFITSIO reads or writes to either (logical) file, it makes sure +that any modifications made to the other file have been completely +flushed from the internal buffers to the file. Thus, in principle, one +could open a file twice, in one case pointing to the first extension +and in the other pointing to the 2nd extension and then write data to +both extensions, in any order, without danger of corrupting the file. +There may be some efficiency penalties in doing this however, since +CFITSIO has to flush all the internal buffers related to one file +before switching to the other, so it would still be prudent to +minimize the number of times one switches back and forth between doing +I/O to different HDUs in the same file. + +Some restriction apply: a FITS file cannot be opened the first time +with READONLY access, and then opened a second time with READWRITE access, +because this may be phyically impossible (e.g., if the file resides +on read-only media such as a CDROM). Also, in multi-threaded environoments, +one should never open the same file with write access in different threads. + +**L. When the Final Size of the FITS HDU is Unknown + +It is not required to know the total size of a FITS data array or table +before beginning to write the data to the FITS file. In the case of +the primary array or an image extension, one should initially create +the array with the size of the highest dimension (largest NAXISn +keyword) set to a dummy value, such as 1. Then after all the data have +been written and the true dimensions are known, then the NAXISn value +should be updated using the fits\_update\_key routine before moving to +another extension or closing the FITS file. + +When writing to FITS tables, CFITSIO automatically keeps track of the +highest row number that is written to, and will increase the size of +the table if necessary. CFITSIO will also automatically insert space +in the FITS file if necessary, to ensure that the data 'heap', if it +exists, and/or any additional HDUs that follow the table do not get +overwritten as new rows are written to the table. + +As a general rule it is best to specify the initial number of rows = 0 +when the table is created, then let CFITSIO keep track of the number of +rows that are actually written. The application program should not +manually update the number of rows in the table (as given by the NAXIS2 +keyword) since CFITSIO does this automatically. If a table is +initially created with more than zero rows, then this will usually be +considered as the minimum size of the table, even if fewer rows are +actually written to the table. Thus, if a table is initially created +with NAXIS2 = 20, and CFITSIO only writes 10 rows of data before +closing the table, then NAXIS2 will remain equal to 20. If however, 30 +rows of data are written to this table, then NAXIS2 will be increased +from 20 to 30. The one exception to this automatic updating of the +NAXIS2 keyword is if the application program directly modifies the +value of NAXIS2 (up or down) itself just before closing the table. In this +case, CFITSIO does not update NAXIS2 again, since it assumes that the +application program must have had a good reason for changing the value +directly. This is not recommended, however, and is only provided for +backward compatibility with software that initially creates a table +with a large number of rows, than decreases the NAXIS2 value to the +actual smaller value just before closing the table. + +**M. CFITSIO Size Limitations + +CFITSIO places very few restrictions on the size of FITS files that it +reads or writes. There are a few limits, however, that may affect +some extreme cases: + +1. The maximum number of FITS files that may be simultaneously opened +by CFITSIO is set by NMAXFILES as defined in fitsio2.h. It is currently +set = 300 by default. CFITSIO will allocate about 80 * NMAXFILES bytes +of memory for internal use. Note that the underlying C compiler or +operating system, may have a smaller limit on the number of opened files. +The C symbolic constant FOPEN\_MAX is intended to define the maximum +number of files that may open at once (including any other text or +binary files that may be open, not just FITS files). On some systems it +has been found that gcc supports a maximum of 255 opened files. + +2. It used to be common for computer systems to only support disk files up +to 2**31 bytes = 2.1 GB in size, but most systems now support larger files. +CFITSIO can optionally read and write these so-called 'large files' that +are greater than 2.1 GB on +platforms where they are supported, but this +usually requires that special compiler option flags be specified to turn +on this option. On linux and solaris systems the compiler flags are +'-D\_LARGEFILE\_SOURCE' and `-D\_FILE\_OFFSET\_BITS=64'. These flags +may also work on other platforms but this has not been tested. Starting +with version 3.0 of CFITSIO, the default Makefile that is distributed +with CFITSIO will include these 2 compiler flags when building on Solaris +and Linux PC systems. Users on other platforms will need to add these +compiler flags manually if they want to support large files. In most +cases it appears that it is not necessary to include these compiler +flags when compiling application code that call the CFITSIO library +routines. + +When CFITSIO is built with large file support (e.g., on Solaris and +Linux PC system by default) then it can read and write FITS data files +on disk that have any of these conditions: + +\begin{itemize} +\item +FITS files larger than 2.1 GB in size +\item +FITS images containing greater than 2.1 G pixels +\item +FITS images that have one dimension with more than 2.1 G pixels +(as given by one of the NAXISn keyword) +\item +FITS tables containing more than 2.1E09 rows (given by the NAXIS2 keyword), +or with rows that are more than 2.1 GB wide (given by the NAXIS1 keyword) +\item +FITS binary tables with a variable-length array heap that is larger +than 2.1 GB (given by the PCOUNT keyword) +\end{itemize} + +The current maximum FITS file size supported by CFITSIO +is about 6 terabytes (containing +2**31 FITS blocks, each 2880 bytes in size). Currently, support for large +files in CFITSIO has been tested on the Linux, Solaris, and IBM AIX +operating systems. + +Note that when writing application programs that are intended to support +large files it is important to use 64-bit integer variables +to store quantities such as the dimensions of images, or the number of +rows in a table. These programs must also call the special versions +of some of the CFITSIO routines that have been adapted to +support 64-bit integers. The names of these routines end in +'ll' ('el' 'el') to distinguish them from the 32-bit integer +version (e.g., fits\_get\_num\_rowsll). + + +*V. Basic CFITSIO Interface Routines + +This chapter describes the basic routines in the CFITSIO user interface +that provide all the functions normally needed to read and write most +FITS files. It is recommended that these routines be used for most +applications and that the more advanced routines described in the +next chapter only be used in special circumstances when necessary. + +The following conventions are used in this chapter in the description +of each function: + +1. Most functions have 2 names: a long descriptive name and a short +concise name. Both names are listed on the first line of the following +descriptions, separated by a slash (/) character. Programmers may use +either name in their programs but the long names are recommended to +help document the code and make it easier to read. + +2. A right arrow symbol ($>$) is used in the function descriptions to +separate the input parameters from the output parameters in the +definition of each routine. This symbol is not actually part of the C +calling sequence. + +3. The function parameters are defined in more detail in the +alphabetical listing in Appendix B. + +4. The first argument in almost all the functions is a pointer to a +structure of type `fitsfile'. Memory for this structure is allocated +by CFITSIO when the FITS file is first opened or created and is freed +when the FITS file is closed. + +5. The last argument in almost all the functions is the error status +parameter. It must be equal to 0 on input, otherwise the function will +immediately exit without doing anything. A non-zero output value +indicates that an error occurred in the function. In most cases the +status value is also returned as the value of the function itself. + +**A. CFITSIO Error Status Routines + +>1 Return a descriptive text string (30 char max.) corresponding to +> a CFITSIO error status code.\label{ffgerr} +- + void fits_get_errstatus / ffgerr (int status, > char *err_text) +- +>2 Return the top (oldest) 80-character error message from the + internal CFITSIO stack of error messages and shift any remaining + messages on the stack up one level. Call this routine + repeatedly to get each message in sequence. The function returns + a value = 0 and a null error message when the error stack is empty. +>\label{ffgmsg} +- + int fits_read_errmsg / ffgmsg (char *err_msg) +- +>3 Print out the error message corresponding to the input status + value and all the error messages on the CFITSIO stack to the specified + file stream (normally to stdout or stderr). If the input + status value = 0 then this routine does nothing. +>\label{ffrprt} +- + void fits_report_error / ffrprt (FILE *stream, status) +- +>4 The fits\_write\_errmark routine puts an invisible marker on the + CFITSIO error stack. The fits\_clear\_errmark routine can then be + used to delete any more recent error messages on the stack, back to + the position of the marker. This preserves any older error messages + on the stack. The fits\_clear\_errmsg routine simply clears all the + messages (and marks) from the stack. These routines are called + without any arguments. +>\label{ffpmrk} \label{ffcmsg} +- + void fits_write_errmark / ffpmrk (void) + void fits_clear_errmark / ffcmrk (void) + void fits_clear_errmsg / ffcmsg (void) +- + +**B. FITS File Access Routines + +>1 Open an existing data file. \label{ffopen} + +- +int fits_open_file / ffopen + (fitsfile **fptr, char *filename, int iomode, > int *status) + +int fits_open_diskfile / ffdkopen + (fitsfile **fptr, char *filename, int iomode, > int *status) + +int fits_open_data / ffdopn + (fitsfile **fptr, char *filename, int iomode, > int *status) + +int fits_open_table / fftopn + (fitsfile **fptr, char *filename, int iomode, > int *status) + +int fits_open_image / ffiopn + (fitsfile **fptr, char *filename, int iomode, > int *status) +- + +The iomode parameter determines the read/write access allowed in the +file and can have values of READONLY (0) or READWRITE (1). The filename +parameter gives the name of the file to be opened, followed by an +optional argument giving the name or index number of the extension +within the FITS file that should be moved to and opened (e.g., +\verb-myfile.fits+3- or \verb-myfile.fits[3]- moves to the 3rd extension within +the file, and \verb-myfile.fits[events]- moves to the extension with the +keyword EXTNAME = 'EVENTS'). + +The fits\_open\_diskfile routine is similar to the fits\_open\_file routine +except that it does not support the extended filename syntax in the input +file name. This routine simply tries to open the specified input file +on magnetic disk. This routine is mainly for use in cases where the +filename (or directory path) contains square or curly bracket characters +that would confuse the extended filename parser. + +The fits\_open\_data routine is similar to the fits\_open\_file routine +except that it will move to the first HDU containing significant data, +if a HDU name or number to open was not explicitly specified as +part of the filename. In this case, it will look for the first +IMAGE HDU with NAXIS greater than 0, or the first table that does not contain the +strings `GTI' (Good Time Interval extension) or `OBSTABLE' in the +EXTNAME keyword value. + +The fits\_open\_table and fits\_open\_image routines are similar to +fits\_open\_data except they will move to the first significant table +HDU or image HDU in the file, respectively, if a HDU name or +number is not specified as part of the filename. + +IRAF images (.imh format files) and raw binary data arrays may also be +opened with READONLY access. CFITSIO will automatically test if the +input file is an IRAF image, and if, so will convert it on the fly into +a virtual FITS image before it is opened by the application program. +If the input file is a raw binary data array of numbers, then the data type +and dimensions of the array must be specified in square brackets +following the name of the file (e.g. 'rawfile.dat[i512,512]' opens a +512 x 512 short integer image). See the `Extended File Name Syntax' +chapter for more details on how to specify the raw file name. The raw +file is converted on the fly into a virtual FITS image in memory that +is then opened by the application program with READONLY access. + +Programs can read the input file from the 'stdin' file stream if a dash +character ('-') is given as the filename. Files can also be opened over +the network using FTP or HTTP protocols by supplying the appropriate URL +as the filename. + +The input file can be modified in various ways to create a virtual file +(usually stored in memory) that is then opened by the application +program by supplying a filtering or binning specifier in square brackets +following the filename. Some of the more common filtering methods are +illustrated in the following paragraphs, but users should refer to the +'Extended File Name Syntax' chapter for a complete description of +the full file filtering syntax. + +When opening an image, a rectangular subset of the physical image may be +opened by listing the first and last pixel in each dimension (and +optional pixel skipping factor): +- +myimage.fits[101:200,301:400] +- +will create and open a 100x100 pixel virtual image of that section of +the physical image, and \verb+myimage.fits[*,-*]+ opens a virtual image +that is the same size as the physical image but has been flipped in +the vertical direction. + +When opening a table, the filtering syntax can be used to add or delete +columns or keywords in the virtual table: +\verb-myfile.fits[events][col !time; PI = PHA*1.2]- opens a virtual table in which the TIME column +has been deleted and a new PI column has been added with a value 1.2 +times that of the PHA column. Similarly, one can filter a table to keep +only those rows that satisfy a selection criterion: +\verb-myfile.fits[events][pha > 50]- creates and opens a virtual table +containing only those rows with a PHA value greater than 50. A large +number of boolean and mathematical operators can be used in the +selection expression. One can also filter table rows using 'Good Time +Interval' extensions, and spatial region filters as in +\verb-myfile.fits[events][gtifilter()]- and +\verb-myfile.fits[events][regfilter( "stars.rng")]-. + +Finally, table columns may be binned or histogrammed to generate a +virtual image. For example, \verb-myfile.fits[events][bin (X,Y)=4]- will +result in a 2-dimensional image calculated by binning the X and Y +columns in the event table with a bin size of 4 in each dimension. The +TLMINn and TLMAXn keywords will be used by default to determine the +range of the image. + +A single program can open the same FITS file more than once and then +treat the resulting fitsfile pointers as though they were completely +independent FITS files. Using this facility, a program can open a FITS +file twice, move to 2 different extensions within the file, and then +> read and write data in those extensions in any order. + +>2 Create and open a new empty output FITS file. \label{ffinit} + +- +int fits_create_file / ffinit + (fitsfile **fptr, char *filename, > int *status) + +int fits_create_diskfile / ffdkinit + (fitsfile **fptr, char *filename, > int *status) +- + +An error will be returned if the specified file already exists, unless +the filename is prefixed with an exclamation point (!). In that case +CFITSIO will overwrite (delete) any existing file with the same name. +Note that the exclamation point is a special UNIX character so if +it is used on the command line it must be preceded by a backslash to +force the UNIX shell to accept the character as part of the filename. + +The output file will be written to the 'stdout' file stream if a dash +character ('-') or the string 'stdout' is given as the filename. Similarly, +'-.gz' or 'stdout.gz' will cause the file to be gzip compressed before +it is written out to the stdout stream. + +Optionally, the name of a template file that is used to define the +structure of the new file may be specified in parentheses following the +output file name. The template file may be another FITS file, in which +case the new file, at the time it is opened, will be an exact copy of +the template file except that the data structures (images and tables) +will be filled with zeros. Alternatively, the template file may be an +ASCII format text file containing directives that define the keywords to be +created in each HDU of the file. See the 'Extended File Name Syntax' + section for a complete description of the template file syntax. + +The fits\_create\_diskfile routine is similar to the fits\_create\_file routine +except that it does not support the extended filename syntax in the input +file name. This routine simply tries to create the specified file +on magnetic disk. This routine is mainly for use in cases where the +filename (or directory path) contains square or curly bracket characters +> that would confuse the extended filename parser. + + +>3 Close a previously opened FITS file. The first routine simply +closes the file, whereas the second one also DELETES THE FILE, which +can be useful in cases where a FITS file has been partially created, +but then an error occurs which prevents it from being completed. +> \label{ffclos} \label{ffdelt} +- + int fits_close_file / ffclos (fitsfile *fptr, > int *status) + + int fits_delete_file / ffdelt (fitsfile *fptr, > int *status) +- +>4 Return the name, I/O mode (READONLY or READWRITE), and/or the file +type (e.g. 'file://', 'ftp://') of the opened FITS file. \label{ffflnm} +> \label{ffflmd} \label{ffurlt} +- + int fits_file_name / ffflnm (fitsfile *fptr, > char *filename, int *status) + + int fits_file_mode / ffflmd (fitsfile *fptr, > int *iomode, int *status) + + int fits_url_type / ffurlt (fitsfile *fptr, > char *urltype, int *status) +- +**C. HDU Access Routines + +The following functions perform operations on Header-Data Units (HDUs) +as a whole. + +>1 Move to a different HDU in the file. The first routine moves to a + specified absolute HDU number (starting with 1 for the primary + array) in the FITS file, and the second routine moves a relative + number HDUs forward or backward from the current HDU. A null + pointer may be given for the hdutype parameter if it's value is not + needed. The third routine moves to the (first) HDU which has the + specified extension type and EXTNAME and EXTVER keyword values (or + HDUNAME and HDUVER keywords). The hdutype parameter may have a + value of IMAGE\_HDU, ASCII\_TBL, BINARY\_TBL, or ANY\_HDU where + ANY\_HDU means that only the extname and extver values will be used + to locate the correct extension. If the input value of extver is 0 + then the EXTVER keyword is ignored and the first HDU with a + matching EXTNAME (or HDUNAME) keyword will be found. If no + matching HDU is found in the file then the current HDU will remain + unchanged and a status = BAD\_HDU\_NUM will be returned. +> \label{ffmahd} \label{ffmrhd} \label{ffmnhd} +- + int fits_movabs_hdu / ffmahd + (fitsfile *fptr, int hdunum, > int *hdutype, int *status) + + int fits_movrel_hdu / ffmrhd + (fitsfile *fptr, int nmove, > int *hdutype, int *status) + + int fits_movnam_hdu / ffmnhd + (fitsfile *fptr, int hdutype, char *extname, int extver, > int *status) +- +>2 Return the total number of HDUs in the FITS file. This returns the +number of completely defined HDUs in the file. If a new HDU has just been added to +the FITS file, then that last HDU will only be counted if it has been closed, +or if data has been written to the HDU. +> The current HDU remains unchanged by this routine. \label{ffthdu} +- + int fits_get_num_hdus / ffthdu + (fitsfile *fptr, > int *hdunum, int *status) +- +>3 Return the number of the current HDU (CHDU) in the FITS file (where + the primary array = 1). This function returns the HDU number +> rather than a status value. \label{ffghdn} +- + int fits_get_hdu_num / ffghdn + (fitsfile *fptr, > int *hdunum) +- +>4 Return the type of the current HDU in the FITS file. The possible +> values for hdutype are: IMAGE\_HDU, ASCII\_TBL, or BINARY\_TBL. \label{ffghdt} +- + int fits_get_hdu_type / ffghdt + (fitsfile *fptr, > int *hdutype, int *status) +- +>5 Copy all or part of the HDUs in the FITS file associated with infptr + and append them to the end of the FITS file associated with + outfptr. If 'previous' is true (not 0), then any HDUs preceding + the current HDU in the input file will be copied to the output + file. Similarly, 'current' and 'following' determine whether the + current HDU, and/or any following HDUs in the input file will be + copied to the output file. Thus, if all 3 parameters are true, then the + entire input file will be copied. On exit, the current HDU in + the input file will be unchanged, and the last HDU in the output +> file will be the current HDU. \label{ffcpfl} +- + int fits_copy_file / ffcpfl + (fitsfile *infptr, fitsfile *outfptr, int previous, int current, + int following, > int *status) +- +>6 Copy the current HDU from the FITS file associated with infptr and append it + to the end of the FITS file associated with outfptr. Space may be +> reserved for MOREKEYS additional keywords in the output header. \label{ffcopy} +- + int fits_copy_hdu / ffcopy + (fitsfile *infptr, fitsfile *outfptr, int morekeys, > int *status) +- +>7 Write the current HDU in the input FITS file to the +> output FILE stream (e.g., to stdout). \label{ffwrhdu} +- + int fits_write_hdu / ffwrhdu + (fitsfile *infptr, FILE *stream, > int *status) +- +>8 Copy the header (and not the data) from the CHDU associated with infptr + to the CHDU associated with outfptr. If the current output HDU + is not completely empty, then the CHDU will be closed and a new + HDU will be appended to the output file. An empty output data unit +> will be created with all values initially = 0). \label{ffcphd} +- + int fits_copy_header / ffcphd + (fitsfile *infptr, fitsfile *outfptr, > int *status) +- +>9 Delete the CHDU in the FITS file. Any following HDUs will be shifted + forward in the file, to fill in the gap created by the deleted + HDU. In the case of deleting the primary array (the first HDU in + the file) then the current primary array will be replace by a null + primary array containing the minimum set of required keywords and + no data. If there are more extensions in the file following the + one that is deleted, then the the CHDU will be redefined to point + to the following extension. If there are no following extensions + then the CHDU will be redefined to point to the previous HDU. The + output hdutype parameter returns the type of the new CHDU. A null + pointer may be given for +> hdutype if the returned value is not needed. \label{ffdhdu} +- + int fits_delete_hdu / ffdhdu + (fitsfile *fptr, > int *hdutype, int *status) +- +**D. Header Keyword Read/Write Routines + +These routines read or write keywords in the Current Header Unit +(CHU). Wild card characters (*, ?, or \#) may be used when specifying +the name of the keyword to be read: a '?' will match any single +character at that position in the keyword name and a '*' will match any +length (including zero) string of characters. The '\#' character will +match any consecutive string of decimal digits (0 - 9). When a wild +card is used the routine will only search for a match from the current +header position to the end of the header and will not resume the search +from the top of the header back to the original header position as is +done when no wildcards are included in the keyword name. The +fits\_read\_record routine may be used to set the starting position +when doing wild card searches. A status value of KEY\_NO\_EXIST is +returned if the specified keyword to be read is not found in the +header. + +***1. Keyword Reading Routines + +>1 Return the number of existing keywords (not counting the + END keyword) and the amount of space currently available for more + keywords. It returns morekeys = -1 if the header has not yet been + closed. Note that CFITSIO will dynamically add space if required + when writing new keywords to a header so in practice there is no + limit to the number of keywords that can be added to a header. A + null pointer may be entered for the morekeys parameter if it's +> value is not needed. \label{ffghsp} +- + int fits_get_hdrspace / ffghsp + (fitsfile *fptr, > int *keysexist, int *morekeys, int *status) +- +>2 Return the specified keyword. In the first routine, + the datatype parameter specifies the desired returned data type of the + keyword value and can have one of the following symbolic constant + values: TSTRING, TLOGICAL (== int), TBYTE, TSHORT, TUSHORT, TINT, + TUINT, TLONG, TULONG, TLONGLONG, TFLOAT, TDOUBLE, TCOMPLEX, and TDBLCOMPLEX. + Within the context of this routine, TSTRING corresponds to a + 'char*' data type, i.e., a pointer to a character array. Data type + conversion will be performed for numeric values if the keyword + value does not have the same data type. If the value of the keyword + is undefined (i.e., the value field is blank) then an error status + = VALUE\_UNDEFINED will be returned. + + The second routine returns the keyword value as a character string + (a literal copy of what is in the value field) regardless of the + intrinsic data type of the keyword. The third routine returns + the entire 80-character header record of the keyword, with any + trailing blank characters stripped off. The fourth routine returns + the (next) header record that contains the literal string of characters + specified by the 'string' argument. + + If a NULL comment pointer is supplied then the comment string +> will not be returned. \label{ffgky} \label{ffgkey} \label{ffgcrd} +- + int fits_read_key / ffgky + (fitsfile *fptr, int datatype, char *keyname, > DTYPE *value, + char *comment, int *status) + + int fits_read_keyword / ffgkey + (fitsfile *fptr, char *keyname, > char *value, char *comment, + int *status) + + int fits_read_card / ffgcrd + (fitsfile *fptr, char *keyname, > char *card, int *status) + + int fits_read_str / ffgstr + (fitsfile *fptr, char *string, > char *card, int *status) +- +>3 Return the nth header record in the CHU. The first keyword + in the header is at keynum = 1; if keynum = 0 then these routines + simply reset the internal CFITSIO pointer to the beginning of the header + so that subsequent keyword operations will start at the top of the + header (e.g., prior to searching for keywords using wild cards in + the keyword name). The first routine returns the entire + 80-character header record (with trailing blanks truncated), + while the second routine parses the record and returns the name, + value, and comment fields as separate (blank truncated) + character strings. If a NULL comment pointer is given on input, + then the comment string will not be +> returned. \label{ffgrec} \label{ffgkyn} +- + int fits_read_record / ffgrec + (fitsfile *fptr, int keynum, > char *card, int *status) + + int fits_read_keyn / ffgkyn + (fitsfile *fptr, int keynum, > char *keyname, char *value, + char *comment, int *status) +- +>4 Return the next keyword whose name matches one of the strings in + 'inclist' but does not match any of the strings in 'exclist'. + The strings in inclist and exclist may contain wild card characters + (*, ?, and \#) as described at the beginning of this section. + This routine searches from the current header position to the + end of the header, only, and does not continue the search from + the top of the header back to the original position. The current + header position may be reset with the ffgrec routine. Note + that nexc may be set = 0 if there are no keywords to be excluded. + This routine returns status = KEY\_NO\_EXIST if a matching +> keyword is not found. \label{ffgnxk} +- + int fits_find_nextkey / ffgnxk + (fitsfile *fptr, char **inclist, int ninc, char **exclist, + int nexc, > char *card, int *status) +- +>5 Return the physical units string from an existing keyword. This + routine uses a local convention, shown in the following example, + in which the keyword units are enclosed in square brackets in the + beginning of the keyword comment field. A null string is returned +> if no units are defined for the keyword. \label{ffgunt} +- + VELOCITY= 12.3 / [km/s] orbital speed + + int fits_read_key_unit / ffgunt + (fitsfile *fptr, char *keyname, > char *unit, int *status) +- +>6 Concatenate the header keywords in the CHDU into a single long + string of characters. This provides a convenient way of passing + all or part of the header information in a FITS HDU to other subroutines. + Each 80-character fixed-length keyword record is appended to the + output character string, in order, with no intervening separator or + terminating characters. The last header record is terminated with + a NULL character. These routine allocates memory for the returned + character array, so the calling program must free the memory when + finished. The cleanest way to do this is to + call the fits\_free\_memory routine. + + There are 2 related routines: fits\_hdr2str simply concatenates all + the existing keywords in the header; fits\_convert\_hdr2str is similar, + except that if the CHDU is a tile compressed image (stored in a binary + table) then it will first convert that header back to that of the corresponding + normal FITS image before concatenating the keywords. + + Selected keywords may be excluded from the returned character string. + If the second parameter (nocomments) is TRUE (nonzero) then any + COMMENT, HISTORY, or blank keywords in the header will not be copied + to the output string. + + The 'exclist' parameter may be used to supply a list of keywords + that are to be excluded from the output character string. Wild card + characters (*, ?, and \#) may be used in the excluded keyword names. + If no additional keywords are to be excluded, then set nexc = 0 and +> specify NULL for the the **exclist parameter. \label{ffhdr2str} +- + int fits_hdr2str / ffhdr2str + (fitsfile *fptr, int nocomments, char **exclist, int nexc, + > char **header, int *nkeys, int *status) + + int fits_convert_hdr2str / ffcnvthdr2str + (fitsfile *fptr, int nocomments, char **exclist, int nexc, + > char **header, int *nkeys, int *status) +- + +***2. Keyword Writing Routines + +>1 Write a keyword of the appropriate data type into the + CHU. The first routine simply appends a new keyword whereas the + second routine will update the value and comment fields of the + keyword if it already exists, otherwise it appends a new + keyword. Note that the address to the value, and not the value + itself, must be entered. The datatype parameter specifies the + data type of the keyword value with one of the following values: + TSTRING, TLOGICAL (== int), TBYTE, TSHORT, TUSHORT, TINT, TUINT, + TLONG, TLONGLONG, TULONG, TFLOAT, TDOUBLE. Within the context of this + routine, TSTRING corresponds to a 'char*' data type, i.e., a pointer + to a character array. A null pointer may be entered for the + comment parameter in which case the keyword comment +> field will be unmodified or left blank. \label{ffpky} \label{ffuky} +- + int fits_write_key / ffpky + (fitsfile *fptr, int datatype, char *keyname, DTYPE *value, + char *comment, > int *status) + + int fits_update_key / ffuky + (fitsfile *fptr, int datatype, char *keyname, DTYPE *value, + char *comment, > int *status) +- +>2 Write a keyword with a null or undefined value (i.e., the + value field in the keyword is left blank). The first routine + simply appends a new keyword whereas the second routine will update + the value and comment fields of the keyword if it already exists, + otherwise it appends a new keyword. A null pointer may be + entered for the comment parameter in which case the keyword + comment +> field will be unmodified or left blank. \label{ffpkyu} \label{ffukyu} +- + int fits_write_key_null / ffpkyu + (fitsfile *fptr, char *keyname, char *comment, > int *status) + + int fits_update_key_null / ffukyu + (fitsfile *fptr, char *keyname, char *comment, > int *status) +- +>3 Write (append) a COMMENT or HISTORY keyword to the CHU. The comment or + history string will be continued over multiple keywords if it is longer +> than 70 characters. \label{ffpcom} \label{ffphis} +- + int fits_write_comment / ffpcom + (fitsfile *fptr, char *comment, > int *status) + + int fits_write_history / ffphis + (fitsfile *fptr, char *history, > int *status) +- +>4 Write the DATE keyword to the CHU. The keyword value will contain + the current system date as a character string in 'yyyy-mm-ddThh:mm:ss' + format. If a DATE keyword already exists in the header, then this + routine will simply update the keyword value with the current date. +> \label{ffpdat} +- + int fits_write_date / ffpdat + (fitsfile *fptr, > int *status) +- +>5 Write a user specified keyword record into the CHU. This is + a low--level routine which can be used to write any arbitrary + record into the header. The record must conform to the all +> the FITS format requirements. \label{ffprec} +- + int fits_write_record / ffprec + (fitsfile *fptr, char *card, > int *status) +- +>6 Update an 80-character record in the CHU. If a keyword with the input + name already exists, then it is overwritten by the value of card. This + could modify the keyword name as well as the value and comment fields. + If the keyword doesn't already exist then a new keyword card is appended +> to the header. \label{ffucrd} +- + int fits_update_card / ffucrd + (fitsfile *fptr, char *keyname, char *card, > int *status) +- + +>>7 Modify (overwrite) the comment field of an existing keyword. \label{ffmcom} +- + int fits_modify_comment / ffmcom + (fitsfile *fptr, char *keyname, char *comment, > int *status) +- + +>8 Write the physical units string into an existing keyword. This + routine uses a local convention, shown in the following example, + in which the keyword units are enclosed in square brackets in the +> beginning of the keyword comment field. \label{ffpunt} +- + VELOCITY= 12.3 / [km/s] orbital speed + + int fits_write_key_unit / ffpunt + (fitsfile *fptr, char *keyname, char *unit, > int *status) +- +>9 Rename an existing keyword, preserving the current value +> and comment fields. \label{ffmnam} +- + int fits_modify_name / ffmnam + (fitsfile *fptr, char *oldname, char *newname, > int *status) +- +>10 Delete a keyword record. The space occupied by + the keyword is reclaimed by moving all the following header records up + one row in the header. The first routine deletes a keyword at a + specified position in the header (the first keyword is at position 1), + whereas the second routine deletes a specifically named keyword. + Wild card characters may be used when specifying the name of the keyword + to be deleted. The third routine deletes the (next) keyword that contains + the literal character string specified by the 'string' +> argument.\label{ffdrec} \label{ffdkey} +- + int fits_delete_record / ffdrec + (fitsfile *fptr, int keynum, > int *status) + + int fits_delete_key / ffdkey + (fitsfile *fptr, char *keyname, > int *status) + + int fits_delete_str / ffdstr + (fitsfile *fptr, char *string, > int *status) +- +**E. Primary Array or IMAGE Extension I/O Routines + +These routines read or write data values in the primary data array (i.e., +the first HDU in a FITS file) or an IMAGE extension. There are also +routines to get information about the data type and size of the image. +Users should also read the following chapter on the CFITSIO iterator +function which provides a more `object oriented' method of reading and +writing images. The iterator function is a little more complicated to +use, but the advantages are that it usually takes less code to perform +the same operation, and the resulting program often runs faster because +the FITS files are read and written using the most efficient block size. + +C programmers should note that the ordering of arrays in FITS files, and +hence in all the CFITSIO calls, is more similar to the dimensionality +of arrays in Fortran rather than C. For instance if a FITS image has +NAXIS1 = 100 and NAXIS2 = 50, then a 2-D array just large enough to hold +the image should be declared as array[50][100] and not as array[100][50]. + +The `datatype' parameter specifies the data type of the `nulval' and +`array' pointers and can have one of the following values: TBYTE, +TSBYTE, TSHORT, TUSHORT, TINT, TUINT, TLONG, TLONGLONG, TULONG, TFLOAT, +TDOUBLE. Automatic data type conversion is performed if the data type +of the FITS array (as defined by the BITPIX keyword) differs from that +specified by 'datatype'. The data values are also automatically scaled +by the BSCALE and BZERO keyword values as they are being read or written +in the FITS array. + +>1 Get the data type or equivalent data type of the image. The + first routine returns the physical data type of the FITS image, as + given by the BITPIX keyword, with allowed values of BYTE\_IMG (8), + SHORT\_IMG (16), LONG\_IMG (32), LONGLONG\_IMG (64), + FLOAT\_IMG (-32), and DOUBLE\_IMG + (-64). + The second routine is similar, except that if the image pixel + values are scaled, with non-default values for the BZERO and BSCALE + keywords, then the routine will return the 'equivalent' data type + that is needed to store the scaled values. For example, if BITPIX + = 16 and BSCALE = 0.1 then the equivalent data type is FLOAT\_IMG. + Similarly if BITPIX = 16, BSCALE = 1, and BZERO = 32768, then the + the pixel values span the range of an unsigned short integer and +> the returned data type will be USHORT\_IMG. \label{ffgidt} +- + int fits_get_img_type / ffgidt + (fitsfile *fptr, > int *bitpix, int *status) + + int fits_get_img_equivtype / ffgiet + (fitsfile *fptr, > int *bitpix, int *status) +- +>2 Get the number of dimensions, and/or the size of + each dimension in the image . The number of axes in the image is + given by naxis, and the size of each dimension is given by the + naxes array (a maximum of maxdim dimensions will be returned). +> \label{ffgidm} \label{ffgisz} \label{ffgipr} +- + int fits_get_img_dim / ffgidm + (fitsfile *fptr, > int *naxis, int *status) + + int fits_get_img_size / ffgisz + (fitsfile *fptr, int maxdim, > long *naxes, int *status) + + int fits_get_img_sizell / ffgiszll + (fitsfile *fptr, int maxdim, > LONGLONG *naxes, int *status) + + int fits_get_img_param / ffgipr + (fitsfile *fptr, int maxdim, > int *bitpix, int *naxis, long *naxes, + int *status) + + int fits_get_img_paramll / ffgiprll + (fitsfile *fptr, int maxdim, > int *bitpix, int *naxis, LONGLONG *naxes, + int *status) +- +>3 Create a new primary array or IMAGE extension with a specified + data type and size. If the FITS file is currently empty then a + primary array is created, otherwise a new IMAGE extension is +> appended to the file. \label{ffcrim} +- + int fits_create_img / ffcrim + ( fitsfile *fptr, int bitpix, int naxis, long *naxes, > int *status) + + int fits_create_imgll / ffcrimll + ( fitsfile *fptr, int bitpix, int naxis, LONGLONG *naxes, > int *status) +- +>4 Copy an n-dimensional image in a particular row and column of a + binary table (in a vector column) + to or from a primary array or image extension. + + The 'cell2image' routine + will append a new image extension (or primary array) to the output file. + Any WCS keywords associated with the input column image will be translated + into the appropriate form for an image extension. Any other keywords + in the table header that are not specifically related to defining the + binary table structure or to other columns in the table + will also be copied to the header of the output image. + + The 'image2cell' routine will copy the input image into the specified row + and column of the current binary table in the output file. The binary table + HDU must exist before calling this routine, but it + may be empty, with no rows or columns of data. The specified column + (and row) will be created if it does not already exist. The 'copykeyflag' + parameter controls which keywords are copied from the input + image to the header of the output table: 0 = no keywords will be copied, + 1 = all keywords will be copied (except those keywords that would be invalid in +> the table header), and 2 = copy only the WCS keywords. \label{copycell} +- + int fits_copy_cell2image + (fitsfile *infptr, fitsfile *outfptr, char *colname, long rownum, + > int *status) + + int fits_copy_image2cell + (fitsfile *infptr, fitsfile *outfptr, char *colname, long rownum, + int copykeyflag > int *status) +- + +>5 Write a rectangular subimage (or the whole image) to the FITS data + array. The fpixel and lpixel arrays give the coordinates of the + first (lower left corner) and last (upper right corner) pixels in +> FITS image to be written to. \label{ffpss} +- + int fits_write_subset / ffpss + (fitsfile *fptr, int datatype, long *fpixel, long *lpixel, + DTYPE *array, > int *status) +- +>6 Write pixels into the FITS data array. 'fpixel' is an array of + length NAXIS which gives the coordinate of the starting pixel to be + written to, such that fpixel[0] is in the range 1 to NAXIS1, + fpixel[1] is in the range 1 to NAXIS2, etc. The first pair of routines + simply writes the array of pixels to the FITS file (doing data type + conversion if necessary) whereas the second routines will substitute + the appropriate FITS null value for any elements which are equal to + the input value of nulval (note that this parameter gives the + address of the null value, not the null value itself). For integer + FITS arrays, the FITS null value is defined by the BLANK keyword (an + error is returned if the BLANK keyword doesn't exist). For floating + point FITS arrays the special IEEE NaN (Not-a-Number) value will be + written into the FITS file. If a null pointer is entered for + nulval, then the null value is ignored and this routine behaves +> the same as fits\_write\_pix. \label{ffppx} \label{ffppxn} +- + int fits_write_pix / ffppx + (fitsfile *fptr, int datatype, long *fpixel, LONGLONG nelements, + DTYPE *array, int *status); + + int fits_write_pixll / ffppxll + (fitsfile *fptr, int datatype, LONGLONG *fpixel, LONGLONG nelements, + DTYPE *array, int *status); + + int fits_write_pixnull / ffppxn + (fitsfile *fptr, int datatype, long *fpixel, LONGLONG nelements, + DTYPE *array, DTYPE *nulval, > int *status); + + int fits_write_pixnullll / ffppxnll + (fitsfile *fptr, int datatype, LONGLONG *fpixel, LONGLONG nelements, + DTYPE *array, DTYPE *nulval, > int *status); +- +>7 Set FITS data array elements equal to the appropriate null pixel + value. For integer FITS arrays, the FITS null value is defined by + the BLANK keyword (an error is returned if the BLANK keyword + doesn't exist). For floating point FITS arrays the special IEEE NaN + (Not-a-Number) value will be written into the FITS file. Note that + 'firstelem' is a scalar giving the offset to the first pixel to be +> written in the equivalent 1-dimensional array of image pixels. \label{ffpprn} +- + int fits_write_null_img / ffpprn + (fitsfile *fptr, LONGLONG firstelem, LONGLONG nelements, > int *status) +- +>8 Read a rectangular subimage (or the whole image) from the FITS + data array. The fpixel and lpixel arrays give the coordinates of + the first (lower left corner) and last (upper right corner) pixels + to be read from the FITS image. Undefined FITS array elements will + be returned with a value = *nullval, (note that this parameter + gives the address of the null value, not the null value itself) + unless nulval = 0 or *nulval = 0, in which case no checks for +> undefined pixels will be performed. \label{ffgsv} +- + int fits_read_subset / ffgsv + (fitsfile *fptr, int datatype, long *fpixel, long *lpixel, long *inc, + DTYPE *nulval, > DTYPE *array, int *anynul, int *status) +- +>9 Read pixels from the FITS data array. 'fpixel' is the starting + pixel location and is an array of length NAXIS such that fpixel[0] + is in the range 1 to NAXIS1, fpixel[1] is in the range 1 to NAXIS2, + etc. The nelements parameter specifies the number of pixels to + read. If fpixel is set to the first pixel, and nelements is set + equal to the NAXIS1 value, then this routine would read the first + row of the image. Alternatively, if nelements is set equal to + NAXIS1 * NAXIS2 then it would read an entire 2D image, or the first + plane of a 3-D datacube. + + The first 2 routines will return any undefined pixels in the FITS array + equal to the value of *nullval (note that this parameter gives the + address of the null value, not the null value itself) unless nulval + = 0 or *nulval = 0, in which case no checks for undefined pixels + will be performed. The second 2 routines are similar except that any + undefined pixels will have the corresponding nullarray element set +> equal to TRUE (= 1). \label{ffgpxv} \label{ffgpxf} +- + int fits_read_pix / ffgpxv + (fitsfile *fptr, int datatype, long *fpixel, LONGLONG nelements, + DTYPE *nulval, > DTYPE *array, int *anynul, int *status) + + int fits_read_pixll / ffgpxvll + (fitsfile *fptr, int datatype, LONGLONG *fpixel, LONGLONG nelements, + DTYPE *nulval, > DTYPE *array, int *anynul, int *status) + + int fits_read_pixnull / ffgpxf + (fitsfile *fptr, int datatype, long *fpixel, LONGLONG nelements, + > DTYPE *array, char *nullarray, int *anynul, int *status) + + int fits_read_pixnullll / ffgpxfll + (fitsfile *fptr, int datatype, LONGLONG *fpixel, LONGLONG nelements, + > DTYPE *array, char *nullarray, int *anynul, int *status) +- +>10 Copy a rectangular section of an image and write it to a new + FITS primary image or image extension. The new image HDU is appended + to the end of the output file; all the keywords in the input image + will be copied to the output image. The common WCS keywords will + be updated if necessary to correspond to the coordinates of the section. + The format of the section expression is + same as specifying an image section using the extended file name + syntax (see "Image Section" in Chapter 10). + (Examples: "1:100,1:200", "1:100:2, 1:*:2", "*, -*"). +> \label{ffcpimg} +- + int fits_copy_image_section / ffcpimg + (fitsfile *infptr, fitsfile *outfptr, char *section, int *status) +- + +**F. Image Compression + +CFITSIO transparently supports the 2 methods of image compression described +below. + +1) The entire FITS file may be externally compressed with the gzip or Unix +compress utility programs, producing a *.gz or *.Z file, respectively. When reading +compressed files of this type, CFITSIO first uncompresses the entire file +into memory before performing the requested read operations. Output files +can be directly written in the gzip compressed format if the user-specified +filename ends with `.gz'. In this case, CFITSIO initially writes the +uncompressed file in memory and then compresses it and writes it to disk +when the FITS file is closed, thus saving user disk space. Read and write +access to these compressed FITS files is generally quite fast since all the +I/O is performed in memory; the main limitation with this technique is that +there must be enough available memory (or swap space) to hold the entire +uncompressed FITS file. + +2) CFITSIO also supports the FITS tiled image compression convention in +which the image is subdivided into a grid of rectangular tiles, and each +tile of pixels is individually compressed. The details of this FITS +compression convention are described at the FITS Support Office web site at +http://fits.gsfc.nasa.gov/fits\_registry.html Basically, the compressed +image tiles are stored in rows of a variable length array column in a FITS +binary table, however CFITSIO recognizes that this binary table extension +contains an image and treats it as if it were an IMAGE extension. This +tile-compressed format is especially well suited for compressing very large +images because a) the FITS header keywords remain uncompressed for rapid +read access, and because b) it is possible to extract and uncompress +sections of the image without having to uncompress the entire image. This +format is also much more effective in compressing floating point images +than simply compressing the image using gzip or compress because it +approximates the floating point values with scaled integers which can then +be compressed more efficiently. + +Currently CFITSIO supports 3 general purpose compression algorithms plus +one other special-purpose compression technique that is designed for data +masks with positive integer pixel values. The 3 general purpose algorithms +are GZIP, Rice, and HCOMPRESS, and the special purpose algorithm is the +IRAF pixel list compression technique (PLIO). In principle, any number of +other compression algorithms could also be supported by the FITS tiled +image compression convention. + +The FITS image can be subdivided into any desired rectangular grid of +compression tiles. With the GZIP, Rice, and PLIO algorithms, the default +is to take each row of the image as a tile. The HCOMPRESS algorithm is +inherently 2-dimensional in nature, so the default in this case is to take +16 rows of the image per tile. In most cases it makes little difference what +tiling pattern is used, so the default tiles are usually adequate. In the +case of very small images, it could be more efficient to compress the whole +image as a single tile. Note that the image dimensions are not required to +be an integer multiple of the tile dimensions; if not, then the tiles at the +edges of the image will be smaller than the other tiles. + +The 4 supported image compression algorithms are all 'loss-less' when +applied to integer FITS images; the pixel values are preserved exactly with +no loss of information during the compression and uncompression process. In +addition, the HCOMPRESS algorithm supports a 'lossy' compression mode that +will produce +larger amount of image compression. This is achieved by specifying a non-zero +value for the HCOMPRESS ``scale'' +parameter. Since the amount of compression that is achieved depends directly +on the RMS noise in the image, it is usually more convention +to specify the HCOMPRESS scale factor relative to the RMS noise. +Setting s = 2.5 means use a scale factor that is 2.5 times the calculated RMS noise +in the image tile. In some cases +it may be desirable to specify the exact scaling to be used, +instead of specifying it relative to the calculated noise value. This may +be done by specifying the negative of desired scale value (typically +in the range -2 to -100). + +Very high compression factors (of 100 or more) can be +achieved by using large HCOMPRESS scale values, however, this can produce undesirable +``blocky'' artifacts in the compressed image. A variation of the HCOMPRESS +algorithm (called HSCOMPRESS) can be used in this case to apply a small +amount of smoothing of the image when it is uncompressed to help cover up +these artifacts. This smoothing is purely cosmetic and does not cause any +significant change to the image pixel values. + +Floating point FITS images (which have BITPIX = -32 or -64) usually contain +too much ``noise'' in the least significant bits of the mantissa of the +pixel values to be effectively compressed with any lossless algorithm. +Consequently, floating point images are first quantized into scaled integer +pixel values (and thus throwing away much of the noise) before being +compressed with the specified algorithm (either GZIP, Rice, or HCOMPRESS). +This technique produces much higher compression factors than +simply using the GZIP utility to externally compress the whole FITS file, but it also +means that the original floating value pixel values are not exactly +preserved. When done properly, this integer scaling technique will only +discard the insignificant noise while still preserving all the real +information in the image. The amount of precision that is retained in the +pixel values is controlled by the "quantization level" parameter, q. Larger +values of q will result in compressed images whose pixels more closely match +the floating point pixel values, but at the same time the amount of +compression that is achieved will be reduced. Users should experiment with +different values for this parameter to determine the optimal value that +preserves all the useful information in the image, without needlessly +preserving all the ``noise'' which will hurt the compression efficiency. + +The default value for the quantization scale factor is 16., which means that +scaled integer pixel values will be quantized such that the difference +between adjacent integer values will be 1/16th of the noise level in the +image background. CFITSIO uses an optimized algorithm to accurately estimate +the noise in the image. As an example, if the RMS noise in the background +pixels of an image = 32.0, then the spacing between adjacent scaled +integer pixel values will equal 2.0 by default. Note that the RMS noise is +independently calculated for each tile of the image, so the resulting +integer scaling factor may fluctuate slightly for each tile. In some cases +it may be desirable to specify the exact quantization level to be used, +instead of specifying it relative to the calculated noise value. This may +be done by specifying the negative of desired quantization level for the +value of q. In the previous example, one could specify q = -2.0 so that the +quantized integer levels differ by 2.0. Larger negative values for q means +that the levels are more coarsely spaced, and will produce higher +compression factors. + +There are 2 methods for specifying all the parameters needed to write a FITS +image in the tile compressed format. The parameters may either be specified +at run time as part of the file name of the output compressed FITS file, or +the writing program may call a set of helper CFITSIO subroutines that are provided +for specifying the parameter values, as described below: + +1) At run time, when specifying the name of the output FITS file to be +created, the user can indicate that images should be +written in tile-compressed format by enclosing the compression +parameters in square brackets following the root disk file name +in the following format: +- + [compress NAME T1,T2; q QLEVEL, s HSCALE] +- +where +- + NAME = algorithm name: GZIP, Rice, HCOMPRESS, HSCOMPRSS or PLIO + may be abbreviated to the first letter (or HS for HSCOMPRESS) + T1,T2 = tile dimension (e.g. 100,100 for square tiles 100 pixels wide) + QLEVEL = quantization level for floating point FITS images + HSCALE = HCOMPRESS scale factor; default = 0 which is lossless. +- + +Here are a few examples of this extended syntax: + +- + myfile.fit[compress] - use the default compression algorithm (Rice) + and the default tile size (row by row) + + myfile.fit[compress GZIP] - use the specified compression algorithm; + myfile.fit[compress Rice] only the first letter of the algorithm + myfile.fit[compress PLIO] name is required. + myfile.fit[compress HCOMP] + + myfile.fit[compress R 100,100] - use Rice and 100 x 100 pixel tiles + + myfile.fit[compress R; q 10.0] - quantization level = (RMS-noise) / 10. + myfile.fit[compress HS; s 2.0] - HSCOMPRESS (with smoothing) + and scale = 2.0 * RMS-noise +- + +2) Before calling the CFITSIO routine to write the image header +keywords (e.g., fits\_create\_image) the programmer can call the +routines described below to specify the compression algorithm and the +tiling pattern that is to be used. There are routines for specifying +the various compression parameters and similar routines to +return the current values of the parameters: +\label{ffsetcomp} \label{ffgetcomp} +- + int fits_set_compression_type(fitsfile *fptr, int comptype, int *status) + int fits_set_tile_dim(fitsfile *fptr, int ndim, long *tilesize, int *status) + int fits_set_quantize_level(fitsfile *fptr, float qlevel, int *status) + int fits_set_hcomp_scale(fitsfile *fptr, float scale, int *status) + int fits_set_hcomp_smooth(fitsfile *fptr, int smooth, int *status) + Set smooth = 1 to apply smoothing when uncompressing the image + + int fits_get_compression_type(fitsfile *fptr, int *comptype, int *status) + int fits_get_tile_dim(fitsfile *fptr, int ndim, long *tilesize, int *status) + int fits_get_quantize_level(fitsfile *fptr, float *level, int *status) + int fits_get_hcomp_scale(fitsfile *fptr, float *scale, int *status) + int fits_get_hcomp_smooth(fitsfile *fptr, int *smooth, int *status) +- +4 symbolic constants are defined for use as the value of the +`comptype' parameter: GZIP\_1, RICE\_1, HCOMPRESS\_1 or PLIO\_1. +Entering NULL for +comptype will turn off the tile-compression and cause normal FITS +images to be written. + + +No special action is required by software when read tile-compressed images because +all the CFITSIO routines that read normal uncompressed FITS images also +transparently read images in the tile-compressed format; CFITSIO essentially +treats the binary table that contains the compressed tiles as if +it were an IMAGE extension. + + +The following 2 routines are available for compressing or +or decompressing an image: +- + int fits_img_compress(fitsfile *infptr, fitsfile *outfptr, int *status); + int fits_img_decompress (fitsfile *infptr, fitsfile *outfptr, int *status); +- +Before calling the compression routine, the compression parameters must +first be defined in one of the 2 way described in the previous paragraphs. +There is also a routine to determine if the current HDU contains +a tile compressed image (it returns 1 or 0): +- + int fits_is_compressed_image(fitsfile *fptr, int *status); +- +A small example program called 'imcopy' is included with CFITSIO that +can be used to compress (or uncompress) any FITS image. This +program can be used to experiment with the various compression options +on existing FITS images as shown in these examples: +- +1) imcopy infile.fit 'outfile.fit[compress]' + + This will use the default compression algorithm (Rice) and the + default tile size (row by row) + +2) imcopy infile.fit 'outfile.fit[compress GZIP]' + + This will use the GZIP compression algorithm and the default + tile size (row by row). The allowed compression algorithms are + Rice, GZIP, and PLIO. Only the first letter of the algorithm + name needs to be specified. + +3) imcopy infile.fit 'outfile.fit[compress G 100,100]' + + This will use the GZIP compression algorithm and 100 X 100 pixel + tiles. + +4) imcopy infile.fit 'outfile.fit[compress R 100,100; q 10.0]' + + This will use the Rice compression algorithm, 100 X 100 pixel + tiles, and quantization level = RMSnoise / 10.0 (assuming the + input image has a floating point data type). + +5) imcopy infile.fit outfile.fit + + If the input file is in tile-compressed format, then it will be + uncompressed to the output file. Otherwise, it simply copies + the input image to the output image. + +6) imcopy 'infile.fit[1001:1500,2001:2500]' outfile.fit + + This extracts a 500 X 500 pixel section of the much larger + input image (which may be in tile-compressed format). The + output is a normal uncompressed FITS image. + +7) imcopy 'infile.fit[1001:1500,2001:2500]' outfile.fit.gz + + Same as above, except the output file is externally compressed + using the gzip algorithm. + +- +**G. ASCII and Binary Table Routines + +These routines perform read and write operations on columns of data in +FITS ASCII or Binary tables. Note that in the following discussions, +the first row and column in a table is at position 1 not 0. + +Users should also read the following chapter on the CFITSIO iterator +function which provides a more `object oriented' method of reading and +writing table columns. The iterator function is a little more +complicated to use, but the advantages are that it usually takes less +code to perform the same operation, and the resulting program often +runs faster because the FITS files are read and written using the most +efficient block size. + +***1. Create New Table + +>1 Create a new ASCII or bintable table extension. If + the FITS file is currently empty then a dummy primary array will be + created before appending the table extension to it. The tbltype + parameter defines the type of table and can have values of + ASCII\_TBL or BINARY\_TBL. The naxis2 parameter gives the initial + number of rows to be created in the table, and should normally be + set = 0. CFITSIO will automatically increase the size of the table + as additional rows are written. A non-zero number of rows may be + specified to reserve space for that many rows, even if a fewer + number of rows will be written. The tunit and extname parameters + are optional and a null pointer may be given if they are not + defined. The FITS Standard recommends that only letters, digits, + and the underscore character be used in column names (the ttype + parameter) with no embedded spaces. Trailing blank characters are +> not significant. \label{ffcrtb} +- + int fits_create_tbl / ffcrtb + (fitsfile *fptr, int tbltype, LONGLONG naxis2, int tfields, char *ttype[], + char *tform[], char *tunit[], char *extname, int *status) +- +***2. Column Information Routines + +>1 Get the number of rows or columns in the current FITS table. + The number of rows is given by the NAXIS2 keyword and the + number of columns is given by the TFIELDS keyword in the header +> of the table. \label{ffgnrw} +- + int fits_get_num_rows / ffgnrw + (fitsfile *fptr, > long *nrows, int *status); + + int fits_get_num_rowsll / ffgnrwll + (fitsfile *fptr, > LONGLONG *nrows, int *status); + + int fits_get_num_cols / ffgncl + (fitsfile *fptr, > int *ncols, int *status); +- + +>2 Get the table column number (and name) of the column whose name +matches an input template name. If casesen = CASESEN then the column +name match will be case-sensitive, whereas if casesen = CASEINSEN then +the case will be ignored. As a general rule, the column names should +be treated as case INsensitive. + +The input column name template may be either the exact name of the +column to be searched for, or it may contain wild card characters (*, +?, or \#), or it may contain the integer number of the desired column +(with the first column = 1). The `*' wild card character matches any +sequence of characters (including zero characters) and the `?' +character matches any single character. The \# wildcard will match any +consecutive string of decimal digits (0-9). If more than one column +name in the table matches the template string, then the first match is +returned and the status value will be set to COL\_NOT\_UNIQUE as a +warning that a unique match was not found. To find the other cases +that match the template, call the routine again leaving the input +status value equal to COL\_NOT\_UNIQUE and the next matching name will +then be returned. Repeat this process until a status = +COL\_NOT\_FOUND is returned. + +The FITS Standard recommends that only letters, digits, and the +underscore character be used in column names (with no embedded +spaces). Trailing blank characters are not significant. +> \label{ffgcno} \label{ffgcnn} +- + int fits_get_colnum / ffgcno + (fitsfile *fptr, int casesen, char *templt, > int *colnum, + int *status) + + int fits_get_colname / ffgcnn + (fitsfile *fptr, int casesen, char *templt, > char *colname, + int *colnum, int *status) +- +>3 Return the data type, vector repeat value, and the width in bytes + of a column in an ASCII or binary table. Allowed values for the + data type in ASCII tables are: TSTRING, TSHORT, TLONG, TFLOAT, and + TDOUBLE. Binary tables also support these types: TLOGICAL, TBIT, + TBYTE, TCOMPLEX and TDBLCOMPLEX. The negative of the data type code + value is returned if it is a variable length array column. Note + that in the case of a 'J' 32-bit integer binary table column, this + routine will return data type = TINT32BIT (which in fact is + equivalent to TLONG). With most current C compilers, a value in a + 'J' column has the same size as an 'int' variable, and may not be + equivalent to a 'long' variable, which is 64-bits long on an + increasing number of compilers. + + The 'repeat' parameter returns the vector repeat count on the binary + table TFORMn keyword value. (ASCII table columns always have repeat + = 1). The 'width' parameter returns the width in bytes of a single + column element (e.g., a '10D' binary table column will have width = + 8, an ASCII table 'F12.2' column will have width = 12, and a binary + table'60A' character string column will have width = 60); Note that + CFITSIO supports the local convention for specifying arrays of + fixed length strings within a binary table character column using + the syntax TFORM = 'rAw' where 'r' is the total number of characters + (= the width of the column) and 'w' is the width of a unit string + within the column. Thus if the column has TFORM = '60A12' then this + means that each row of the table contains 5 12-character substrings + within the 60-character field, and thus in this case this routine will + return typecode = TSTRING, repeat = 60, and width = 12. (The TDIMn + keyword may also be used to specify the unit string length; The pair + of keywords TFORMn = '60A' and TDIMn = '(12,5)' would have the + same effect as TFORMn = '60A12'). The number + of substrings in any binary table character string field can be + calculated by (repeat/width). A null pointer may be given for any of + the output parameters that are not needed. + + The second routine, fit\_get\_eqcoltype is similar except that in + the case of scaled integer columns it returns the 'equivalent' data + type that is needed to store the scaled values, and not necessarily + the physical data type of the unscaled values as stored in the FITS + table. For example if a '1I' column in a binary table has TSCALn = + 1 and TZEROn = 32768, then this column effectively contains unsigned + short integer values, and thus the returned value of typecode will + be TUSHORT, not TSHORT. Similarly, if a column has TTYPEn = '1I' + and TSCALn = 0.12, then the returned typecode +> will be TFLOAT. \label{ffgtcl} +- + int fits_get_coltype / ffgtcl + (fitsfile *fptr, int colnum, > int *typecode, long *repeat, + long *width, int *status) + + int fits_get_coltypell / ffgtclll + (fitsfile *fptr, int colnum, > int *typecode, LONGLONG *repeat, + LONGLONG *width, int *status) + + int fits_get_eqcoltype / ffeqty + (fitsfile *fptr, int colnum, > int *typecode, long *repeat, + long *width, int *status) + + int fits_get_eqcoltypell / ffeqtyll + (fitsfile *fptr, int colnum, > int *typecode, LONGLONG *repeat, + LONGLONG *width, int *status) +- +>4 Return the display width of a column. This is the length + of the string that will be returned by the fits\_read\_col routine + when reading the column as a formatted string. The display width is + determined by the TDISPn keyword, if present, otherwise by the data +> type of the column. \label{ffgcdw} +- + int fits_get_col_display_width / ffgcdw + (fitsfile *fptr, int colnum, > int *dispwidth, int *status) +- + +>5 Return the number of and size of the dimensions of a table column in + a binary table. Normally this information is given by the TDIMn keyword, + but if this keyword is not present then this routine returns naxis = 1 +> and naxes[0] equal to the repeat count in the TFORM keyword. \label{ffgtdm} +- + int fits_read_tdim / ffgtdm + (fitsfile *fptr, int colnum, int maxdim, > int *naxis, + long *naxes, int *status) + + int fits_read_tdimll / ffgtdmll + (fitsfile *fptr, int colnum, int maxdim, > int *naxis, + LONGLONG *naxes, int *status) +- +>6 Decode the input TDIMn keyword string (e.g. '(100,200)') and return the + number of and size of the dimensions of a binary table column. If the input + tdimstr character string is null, then this routine returns naxis = 1 + and naxes[0] equal to the repeat count in the TFORM keyword. This routine +> is called by fits\_read\_tdim. \label{ffdtdm} +- + int fits_decode_tdim / ffdtdm + (fitsfile *fptr, char *tdimstr, int colnum, int maxdim, > int *naxis, + long *naxes, int *status) + + int fits_decode_tdimll / ffdtdmll + (fitsfile *fptr, char *tdimstr, int colnum, int maxdim, > int *naxis, + LONGLONG *naxes, int *status) +- +>7 Write a TDIMn keyword whose value has the form '(l,m,n...)' + where l, m, n... are the dimensions of a multidimensional array +> column in a binary table. \label{ffptdm} +- + int fits_write_tdim / ffptdm + (fitsfile *fptr, int colnum, int naxis, long *naxes, > int *status) + + int fits_write_tdimll / ffptdmll + (fitsfile *fptr, int colnum, int naxis, LONGLONG *naxes, > int *status) +- + +***3. Routines to Edit Rows or Columns + +>1 Insert or delete rows in an ASCII or binary table. When inserting rows + all the rows following row FROW are shifted down by NROWS rows; if + FROW = 0 then the blank rows are inserted at the beginning of the + table. Note that it is *not* necessary to insert rows in a table before + writing data to those rows (indeed, it would be inefficient to do so). + Instead one may simply write data to any row of the table, whether that + row of data already exists or not. + + The first delete routine deletes NROWS consecutive rows + starting with row FIRSTROW. The second delete routine takes an + input string that lists the rows or row ranges (e.g., + '5-10,12,20-30'), whereas the third delete routine takes an input + integer array that specifies each individual row to be deleted. In + both latter cases, the input list of rows to delete must be sorted + in ascending order. These routines update the NAXIS2 keyword to + reflect the new number of rows in the +> table. \label{ffirow} \label{ffdrow} \label{ffdrws} \label{ffdrrg} +- + int fits_insert_rows / ffirow + (fitsfile *fptr, LONGLONG firstrow, LONGLONG nrows, > int *status) + + int fits_delete_rows / ffdrow + (fitsfile *fptr, LONGLONG firstrow, LONGLONG nrows, > int *status) + + int fits_delete_rowrange / ffdrrg + (fitsfile *fptr, char *rangelist, > int *status) + + int fits_delete_rowlist / ffdrws + (fitsfile *fptr, long *rowlist, long nrows, > int *status) + + int fits_delete_rowlistll / ffdrwsll + (fitsfile *fptr, LONGLONG *rowlist, LONGLONG nrows, > int *status) +- +>2 Insert or delete column(s) in an ASCII or binary + table. When inserting, COLNUM specifies the column number that the + (first) new column should occupy in the table. NCOLS specifies how + many columns are to be inserted. Any existing columns from this + position and higher are shifted over to allow room for the new + column(s). The index number on all the following keywords will be + incremented or decremented if necessary to reflect the new position + of the column(s) in the table: TBCOLn, TFORMn, TTYPEn, TUNITn, + TNULLn, TSCALn, TZEROn, TDISPn, TDIMn, TLMINn, TLMAXn, TDMINn, + TDMAXn, TCTYPn, TCRPXn, TCRVLn, TCDLTn, TCROTn, +> and TCUNIn. \label{fficol} \label{fficls} \label{ffdcol} +- + int fits_insert_col / fficol + (fitsfile *fptr, int colnum, char *ttype, char *tform, + > int *status) + + int fits_insert_cols / fficls + (fitsfile *fptr, int colnum, int ncols, char **ttype, + char **tform, > int *status) + + int fits_delete_col / ffdcol(fitsfile *fptr, int colnum, > int *status) +- +>3 Copy a column from one HDU to another (or to the same HDU). If + create\_col = TRUE, then a new column will be inserted in the output + table, at position `outcolumn', otherwise the existing output column will + be overwritten (in which case it must have a compatible data type). + If outcolnum is greater than the number of column in the table, then + the new column will be appended to the end of the table. + Note that the first column in a table is at colnum = 1. + The standard indexed keywords that related to the column (e.g., TDISPn, +> TUNITn, TCRPXn, TCDLTn, etc.) will also be copied. \label{ffcpcl} +- + int fits_copy_col / ffcpcl + (fitsfile *infptr, fitsfile *outfptr, int incolnum, int outcolnum, + int create_col, > int *status); +- +>4 Copy 'nrows' consecutive rows from one table to another, beginning + with row 'firstrow'. These rows will be appended to any existing + rows in the output table. +> Note that the first row in a table is at row = 1. \label{ffcprw} +- + int fits_copy_rows / ffcprw + (fitsfile *infptr, fitsfile *outfptr, LONGLONG firstrow, + LONGLONG nrows, > int *status); +- +>5 Modify the vector length of a binary table column (e.g., + change a column from TFORMn = '1E' to '20E'). The vector +> length may be increased or decreased from the current value. \label{ffmvec} +- + int fits_modify_vector_len / ffmvec + (fitsfile *fptr, int colnum, LONGLONG newveclen, > int *status) +- +***4. Read and Write Column Data Routines + +The following routines write or read data values in the current ASCII +or binary table extension. If a write operation extends beyond the +current size of the table, then the number of rows in the table will +automatically be increased and the NAXIS2 keyword value will be +updated. Attempts to read beyond the end of the table will result in +an error. + +Automatic data type conversion is performed for numerical data types +(only) if the data type of the column (defined by the TFORMn keyword) +differs from the data type of the array in the calling routine. ASCII and binary +tables support the following data type values: TSTRING, TBYTE, TSBYTE, TSHORT, +TUSHORT, TINT, TUINT, TLONG, TLONGLONG, TULONG, TFLOAT, or TDOUBLE. +Binary tables also support TLOGICAL (internally mapped to the `char' +data type), TCOMPLEX, and TDBLCOMPLEX. + +Note that it is *not* necessary to insert rows in a table before +writing data to those rows (indeed, it would be inefficient to do so). +Instead, one may simply write data to any row of the table, whether that +row of data already exists or not. + +Individual bits in a binary table 'X' or 'B' column may be read/written +to/from a *char array by specifying the TBIT datatype. The *char +array will be interpreted as an array of logical TRUE (1) or FALSE (0) +values that correspond to the value of each bit in the FITS 'X' or 'B' column. +Alternatively, the values in a binary table 'X' column may be read/written +8 bits at a time to/from an array of 8-bit integers by specifying the +TBYTE datatype. + +Note that within the context of these routines, the TSTRING data type +corresponds to a C 'char**' data type, i.e., a pointer to an array of +pointers to an array of characters. This is different from the keyword +reading and writing routines where TSTRING corresponds to a C 'char*' +data type, i.e., a single pointer to an array of characters. When +reading strings from a table, the char arrays obviously must have been +allocated long enough to hold the whole FITS table string. + +Numerical data values are automatically scaled by the TSCALn and TZEROn +keyword values (if they exist). + +In the case of binary tables with vector elements, the 'felem' +parameter defines the starting element (beginning with 1, not 0) within +the cell (a cell is defined as the intersection of a row and a column +and may contain a single value or a vector of values). The felem +parameter is ignored when dealing with ASCII tables. Similarly, in the +case of binary tables the 'nelements' parameter specifies the total +number of vector values to be read or written (continuing on subsequent +rows if required) and not the number of table cells. + +>>1 Write elements into an ASCII or binary table column. + The first routine simply writes the array of values to the FITS file + (doing data type conversion if necessary) whereas the second routine + will substitute the appropriate FITS null value for all elements + which are equal to the input value of nulval (note that this + parameter gives the address of nulval, not the null value + itself). For integer columns the FITS null value is defined by the + TNULLn keyword (an error is returned if the keyword doesn't exist). + For floating point columns the special IEEE NaN (Not-a-Number) + value will be written into the FITS file. If a null pointer is + entered for nulval, then the null value is ignored and this routine + behaves the same as the first routine. The third routine + simply writes undefined pixel values to the column. The fourth routine + fills every column in the table with null values, in the specified + rows (ignoring any columns that do not have a defined null value). + \label{ffpcl} \label{ffpcn} \label{ffpclu} +- + int fits_write_col / ffpcl + (fitsfile *fptr, int datatype, int colnum, LONGLONG firstrow, + LONGLONG firstelem, LONGLONG nelements, DTYPE *array, > int *status) + + int fits_write_colnull / ffpcn + (fitsfile *fptr, int datatype, int colnum, LONGLONG firstrow, + LONGLONG firstelem, LONGLONG nelements, DTYPE *array, DTYPE *nulval, + > int *status) + + int fits_write_col_null / ffpclu + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG firstelem, + LONGLONG nelements, > int *status) + + int fits_write_nullrows / ffprwu + (fitsfile *fptr, LONGLONG firstrow, LONGLONG nelements, > int *status) +- +>2 Read elements from an ASCII or binary table column. The data type + parameter specifies the data type of the `nulval' and `array' pointers; + Undefined array elements will be returned with a value = *nullval, + (note that this parameter gives the address of the null value, not the + null value itself) unless nulval = 0 or *nulval = 0, in which case + no checking for undefined pixels will be performed. The second + routine is similar except that any undefined pixels will have the + corresponding nullarray element set equal to TRUE (= 1). + + Any column, regardless of it's intrinsic data type, may be read as a + string. It should be noted however that reading a numeric column + as a string is 10 - 100 times slower than reading the same column + as a number due to the large overhead in constructing the formatted + strings. The display format of the returned strings will be + determined by the TDISPn keyword, if it exists, otherwise by the + data type of the column. The length of the returned strings (not + including the null terminating character) can be determined with + the fits\_get\_col\_display\_width routine. The following TDISPn + display formats are currently supported: +- + Iw.m Integer + Ow.m Octal integer + Zw.m Hexadecimal integer + Fw.d Fixed floating point + Ew.d Exponential floating point + Dw.d Exponential floating point + Gw.d General; uses Fw.d if significance not lost, else Ew.d +- + where w is the width in characters of the displayed values, m is the minimum + number of digits displayed, and d is the number of digits to the right of the + decimal. The .m field is optional. +> \label{ffgcv} \label{ffgcf} +- + int fits_read_col / ffgcv + (fitsfile *fptr, int datatype, int colnum, LONGLONG firstrow, LONGLONG firstelem, + LONGLONG nelements, DTYPE *nulval, DTYPE *array, int *anynul, int *status) + + int fits_read_colnull / ffgcf + (fitsfile *fptr, int datatype, int colnum, LONGLONG firstrow, LONGLONG firstelem, + LONGLONG nelements, DTYPE *array, char *nullarray, int *anynul, int *status) +- + +***5. Row Selection and Calculator Routines + +These routines all parse and evaluate an input string containing a user +defined arithmetic expression. The first 3 routines select rows in a +FITS table, based on whether the expression evaluates to true (not +equal to zero) or false (zero). The other routines evaluate the +expression and calculate a value for each row of the table. The +allowed expression syntax is described in the row filter section in the +`Extended File Name Syntax' chapter of this document. The expression +may also be written to a text file, and the name of the file, prepended +with a '@' character may be supplied for the 'expr' parameter (e.g. +'@filename.txt'). The expression in the file can be arbitrarily +complex and extend over multiple lines of the file. Lines that begin +with 2 slash characters ('//') will be ignored and may be used to add +comments to the file. + +>1 Evaluate a boolean expression over the indicated rows, returning an + array of flags indicating which rows evaluated to TRUE/FALSE. + Upon return, +> *n\_good\_rows contains the number of rows that evaluate to TRUE. \label{fffrow} +- + int fits_find_rows / fffrow + (fitsfile *fptr, char *expr, long firstrow, long nrows, + > long *n_good_rows, char *row_status, int *status) +- +>>2 Find the first row which satisfies the input boolean expression \label{ffffrw} +- + int fits_find_first_row / ffffrw + (fitsfile *fptr, char *expr, > long *rownum, int *status) +- +>3 Evaluate an expression on all rows of a table. If the input and output +files are not the same, copy the TRUE rows to the output file; if the output +table is not empty, then this routine will append the new +selected rows after the existing rows. If the +>files are the same, delete the FALSE rows (preserve the TRUE rows). \label{ffsrow} +- + int fits_select_rows / ffsrow + (fitsfile *infptr, fitsfile *outfptr, char *expr, > int *status ) +- +>4 Calculate an expression for the indicated rows of a table, returning +the results, cast as datatype (TSHORT, TDOUBLE, etc), in array. If +nulval==NULL, UNDEFs will be zeroed out. For vector results, the number +of elements returned may be less than nelements if nelements is not an +even multiple of the result dimension. Call fits\_test\_expr to obtain +>the dimensions of the results. \label{ffcrow} +- + int fits_calc_rows / ffcrow + (fitsfile *fptr, int datatype, char *expr, long firstrow, + long nelements, void *nulval, > void *array, int *anynul, int *status) +- +>5 Evaluate an expression and write the result either to a column (if +the expression is a function of other columns in the table) or to a +keyword (if the expression evaluates to a constant and is not a +function of other columns in the table). In the former case, the +parName parameter is the name of the column (which may or may not already +exist) into which to write the results, and parInfo contains an +optional TFORM keyword value if a new column is being created. If a +TFORM value is not specified then a default format will be used, +depending on the expression. If the expression evaluates to a constant, +then the result will be written to the keyword name given by the +parName parameter, and the parInfo parameter may be used to supply an +optional comment for the keyword. If the keyword does not already +exist, then the name of the keyword must be preceded with a '\#' character, +> otherwise the result will be written to a column with that name. \label{ffcalc} +- + int fits_calculator / ffcalc + (fitsfile *infptr, char *expr, fitsfile *outfptr, char *parName, + char *parInfo, > int *status) +- +>6 This calculator routine is similar to the previous routine, except +that the expression is only evaluated over the specified +row ranges. nranges specifies the number of row ranges, and firstrow +>and lastrow give the starting and ending row number of each range. \label{ffcalcrng} +- + int fits_calculator_rng / ffcalc_rng + (fitsfile *infptr, char *expr, fitsfile *outfptr, char *parName, + char *parInfo, int nranges, long *firstrow, long *lastrow + > int *status) +- +>7 Evaluate the given expression and return dimension and type information +on the result. The returned dimensions correspond to a single row entry +of the requested expression, and are equivalent to the result of fits\_read\_tdim(). +Note that strings are considered to be one element regardless of string length. +>If maxdim == 0, then naxes is optional. \label{fftexp} +- + int fits_test_expr / fftexp + (fitsfile *fptr, char *expr, int maxdim > int *datatype, long *nelem, int *naxis, + long *naxes, int *status) +- + +***6. Column Binning or Histogramming Routines + +The following routines may be useful when performing histogramming operations on +column(s) of a table to generate an image in a primary array or image extension. + +>1 Calculate the histogramming parameters (min, max, and bin size +for each axis of the histogram, based on a variety of possible input parameters. +If the input names of the columns to be binned are null, then the routine will first +look for the CPREF = "NAME1, NAME2, ..." keyword which lists the preferred +columns. If not present, then the routine will assume the column names X, Y, Z, and T +for up to 4 axes (as specified by the NAXIS parameter). + +MININ and MAXIN are input arrays that give the minimum and maximum value for +the histogram, along each axis. Alternatively, the name of keywords that give +the min, max, and binsize may be give with the MINNAME, MAXNAME, and BINNAME +array parameters. If the value = DOUBLENULLVALUE and no keyword names are +given, then the routine will use the TLMINn and TLMAXn keywords, if present, or the +actual min and/or max values in the column. + +BINSIZEIN is an array giving the binsize along each axis. +If the value = +DOUBLENULLVALUE, and a keyword name is not specified with BINNAME, +then this routine will first look for the TDBINn keyword, or else will +use a binsize = 1, or a binsize that produces 10 histogram bins, which ever +is smaller. +> \label{calcbinning} +- + int fits_calc_binning + Input parameters: + (fitsfile *fptr, /* IO - pointer to table to be binned */ + int naxis, /* I - number of axes/columns in the binned image */ + char colname[4][FLEN_VALUE], /* I - optional column names */ + double *minin, /* I - optional lower bound value for each axis */ + double *maxin, /* I - optional upper bound value, for each axis */ + double *binsizein, /* I - optional bin size along each axis */ + char minname[4][FLEN_VALUE], /* I - optional keywords for min */ + char maxname[4][FLEN_VALUE], /* I - optional keywords for max */ + char binname[4][FLEN_VALUE], /* I - optional keywords for binsize */ + Output parameters: + int *colnum, /* O - column numbers, to be binned */ + long *naxes, /* O - number of bins in each histogram axis */ + float *amin, /* O - lower bound of the histogram axes */ + float *amax, /* O - upper bound of the histogram axes */ + float *binsize, /* O - width of histogram bins/pixels on each axis */ + int *status) +- + +>2 Copy the relevant keywords from the header of the table that is being +binned, to the the header of the output histogram image. This will not +copy the table structure keywords (e.g., NAXIS, TFORMn, TTYPEn, etc.) nor +will it copy the keywords that apply to other columns of the table that are +not used to create the histogram. This routine will translate the names of +the World Coordinate System (WCS) keywords for the binned columns into the +form that is need for a FITS image (e.g., the TCTYPn table keyword will +be translated to the CTYPEn image keyword). +> \label{copypixlist2image} +- + int fits_copy_pixlist2image + (fitsfile *infptr, /* I - pointer to input HDU */ + fitsfile *outfptr, /* I - pointer to output HDU */ + int firstkey, /* I - first HDU keyword to start with */ + int naxis, /* I - number of axes in the image */ + int *colnum, /* I - numbers of the columns to be binned */ + int *status) /* IO - error status */ +- + +>3 Write a set of default WCS keywords to the histogram header, IF the +WCS keywords do not already exist. This will create a linear WCS where +the coordinate types are equal to the original column names. +> \label{writekeyshisto} +- + int fits_write_keys_histo + (fitsfile *fptr, /* I - pointer to table to be binned */ + fitsfile *histptr, /* I - pointer to output histogram image HDU */ + int naxis, /* I - number of axes in the histogram image */ + int *colnum, /* I - column numbers of the binned columns */ + int *status) +- + +>4 Update the WCS keywords in a histogram image header that give the location +of the reference pixel (CRPIXn), and the pixel size (CDELTn), in the binned +image. +> \label{rebinwcs} +- + int fits_rebin_wcs + (fitsfile *fptr, /* I - pointer to table to be binned */ + int naxis, /* I - number of axes in the histogram image */ + float *amin, /* I - first pixel include in each axis */ + float *binsize, /* I - binning factor for each axis */ + int *status) +- + +>5 Bin the values in the input table columns, and write the histogram +array to the output FITS image (histptr). +> \label{makehist} +- + int fits_make_hist + (fitsfile *fptr, /* I - pointer to table with X and Y cols; */ + fitsfile *histptr, /* I - pointer to output FITS image */ + int bitpix, /* I - datatype for image: 16, 32, -32, etc */ + int naxis, /* I - number of axes in the histogram image */ + long *naxes, /* I - size of axes in the histogram image */ + int *colnum, /* I - column numbers (array length = naxis) */ + float *amin, /* I - minimum histogram value, for each axis */ + float *amax, /* I - maximum histogram value, for each axis */ + float *binsize, /* I - bin size along each axis */ + float weight, /* I - binning weighting factor (FLOATNULLVALUE */ + /* for no weighting) */ + int wtcolnum, /* I - keyword or col for weight (or NULL) */ + int recip, /* I - use reciprocal of the weight? 0 or 1 */ + char *selectrow, /* I - optional array (length = no. of */ + /* rows in the table). If the element is true */ + /* then the corresponding row of the table will */ + /* be included in the histogram, otherwise the */ + /* row will be skipped. Ingnored if *selectrow */ + /* is equal to NULL. */ + int *status) +- + + +**H. Utility Routines + +***1. File Checksum Routines + +The following routines either compute or validate the checksums for the +CHDU. The DATASUM keyword is used to store the numerical value of the +32-bit, 1's complement checksum for the data unit alone. If there is +no data unit then the value is set to zero. The numerical value is +stored as an ASCII string of digits, enclosed in quotes, because the +value may be too large to represent as a 32-bit signed integer. The +CHECKSUM keyword is used to store the ASCII encoded COMPLEMENT of the +checksum for the entire HDU. Storing the complement, rather than the +actual checksum, forces the checksum for the whole HDU to equal zero. +If the file has been modified since the checksums were computed, then +the HDU checksum will usually not equal zero. These checksum keyword +conventions are based on a paper by Rob Seaman published in the +proceedings of the ADASS IV conference in Baltimore in November 1994 +and a later revision in June 1995. See Appendix B for the definition +of the parameters used in these routines. + +>1 Compute and write the DATASUM and CHECKSUM keyword values for the CHDU + into the current header. If the keywords already exist, their values + will be updated only if necessary (i.e., if the file + has been modified since the original keyword +> values were computed). \label{ffpcks} +- + int fits_write_chksum / ffpcks + (fitsfile *fptr, > int *status) +- +>2 Update the CHECKSUM keyword value in the CHDU, assuming that the + DATASUM keyword exists and already has the correct value. This routine + calculates the new checksum for the current header unit, adds it to the + data unit checksum, encodes the value into an ASCII string, and writes +> the string to the CHECKSUM keyword. \label{ffupck} +- + int fits_update_chksum / ffupck + (fitsfile *fptr, > int *status) +- +>3 Verify the CHDU by computing the checksums and comparing + them with the keywords. The data unit is verified correctly + if the computed checksum equals the value of the DATASUM + keyword. The checksum for the entire HDU (header plus data unit) is + correct if it equals zero. The output DATAOK and HDUOK parameters + in this routine are integers which will have a value = 1 + if the data or HDU is verified correctly, a value = 0 + if the DATASUM or CHECKSUM keyword is not present, or value = -1 +> if the computed checksum is not correct. \label{ffvcks} +- + int fits_verify_chksum / ffvcks + (fitsfile *fptr, > int *dataok, int *hduok, int *status) +- +>4 Compute and return the checksum values for the CHDU + without creating or modifying the + CHECKSUM and DATASUM keywords. This routine is used internally by +> ffvcks, but may be useful in other situations as well. \label{ffgcks} +- + int fits_get_chksum/ /ffgcks + (fitsfile *fptr, > unsigned long *datasum, unsigned long *hdusum, + int *status) +- +>5 Encode a checksum value + into a 16-character string. If complm is non-zero (true) then the 32-bit +> sum value will be complemented before encoding. \label{ffesum} +- + int fits_encode_chksum / ffesum + (unsigned long sum, int complm, > char *ascii); +- +>6 Decode a 16-character checksum string into a unsigned long value. + If is non-zero (true). then the 32-bit sum value will be complemented + after decoding. The checksum value is also returned as the +> value of the function. \label{ffdsum} +- + unsigned long fits_decode_chksum / ffdsum + (char *ascii, int complm, > unsigned long *sum); +- + +***2. Date and Time Utility Routines + +The following routines help to construct or parse the FITS date/time +strings. Starting in the year 2000, the FITS DATE keyword values (and +the values of other `DATE-' keywords) must have the form 'YYYY-MM-DD' +(date only) or 'YYYY-MM-DDThh:mm:ss.ddd...' (date and time) where the +number of decimal places in the seconds value is optional. These times +are in UTC. The older 'dd/mm/yy' date format may not be used for dates +after 01 January 2000. See Appendix B for the definition of the +parameters used in these routines. + +>1 Get the current system date. C already provides standard + library routines for getting the current date and time, + but this routine is provided for compatibility with + the Fortran FITSIO library. The returned year has 4 digits +> (1999, 2000, etc.) \label{ffgsdt} +- + int fits_get_system_date/ffgsdt + ( > int *day, int *month, int *year, int *status ) +- + +>2 Get the current system date and time string ('YYYY-MM-DDThh:mm:ss'). +The time will be in UTC/GMT if available, as indicated by a returned timeref +value = 0. If the returned value of timeref = 1 then this indicates that +it was not possible to convert the local time to UTC, and thus the local +>time was returned. +- + int fits_get_system_time/ffgstm + (> char *datestr, int *timeref, int *status) +- + +>3 Construct a date string from the input date values. If the year +is between 1900 and 1998, inclusive, then the returned date string will +have the old FITS format ('dd/mm/yy'), otherwise the date string will +have the new FITS format ('YYYY-MM-DD'). Use fits\_time2str instead +> to always return a date string using the new FITS format. \label{ffdt2s} +- + int fits_date2str/ffdt2s + (int year, int month, int day, > char *datestr, int *status) +- + +>4 Construct a new-format date + time string ('YYYY-MM-DDThh:mm:ss.ddd...'). + If the year, month, and day values all = 0 then only the time is encoded + with format 'hh:mm:ss.ddd...'. The decimals parameter specifies how many + decimal places of fractional seconds to include in the string. If `decimals' +> is negative, then only the date will be return ('YYYY-MM-DD'). +- + int fits_time2str/fftm2s + (int year, int month, int day, int hour, int minute, double second, + int decimals, > char *datestr, int *status) +- + +>5 Return the date as read from the input string, where the string may be +in either the old ('dd/mm/yy') or new ('YYYY-MM-DDThh:mm:ss' or +'YYYY-MM-DD') FITS format. Null pointers may be supplied for any +> unwanted output date parameters. +- + int fits_str2date/ffs2dt + (char *datestr, > int *year, int *month, int *day, int *status) +- + +>6 Return the date and time as read from the input string, where the +string may be in either the old or new FITS format. The returned hours, +minutes, and seconds values will be set to zero if the input string +does not include the time ('dd/mm/yy' or 'YYYY-MM-DD') . Similarly, +the returned year, month, and date values will be set to zero if the +date is not included in the input string ('hh:mm:ss.ddd...'). Null +pointers may be supplied for any unwanted output date and time +>parameters. +- + int fits_str2time/ffs2tm + (char *datestr, > int *year, int *month, int *day, int *hour, + int *minute, double *second, int *status) +- + +***3. General Utility Routines + +The following utility routines may be useful for certain applications. + +>1 Return the revision number of the CFITSIO library. + The revision number will be incremented with each new +> release of CFITSIO. \label{ffvers} +- + float fits_get_version / ffvers ( > float *version) +- +>2 Write an 80-character message to the CFITSIO error stack. Application + programs should not normally write to the stack, but there may be +> some situations where this is desirable. \label{ffpmsg} +- + void fits_write_errmsg / ffpmsg (char *err_msg) +- +>>3 Convert a character string to uppercase (operates in place). \label{ffupch} +- + void fits_uppercase / ffupch (char *string) +- +>4 Compare the input template string against the reference string + to see if they match. The template string may contain wildcard + characters: '*' will match any sequence of characters (including + zero characters) and '?' will match any single character in the + reference string. The '\#' character will match any consecutive string + of decimal digits (0 - 9). If casesen = CASESEN = TRUE then the match will + be case sensitive, otherwise the case of the letters will be ignored + if casesen = CASEINSEN = FALSE. The returned MATCH parameter will be + TRUE if the 2 strings match, and EXACT will be TRUE if the match is + exact (i.e., if no wildcard characters were used in the match). +> Both strings must be 68 characters or less in length. \label{ffcmps} +- + void fits_compare_str / ffcmps + (char *templt, char *string, int casesen, > int *match, int *exact) +- +>5 Split a string containing a list of names (typically file names or column + names) into individual name tokens by a sequence of calls to + fits\_split\_names. The names in the list must be delimited by a comma + and/or spaces. This routine ignores spaces and commas that occur + within parentheses, brackets, or curly brackets. It also strips any + leading and trailing blanks from the returned name. + + This routine is similar to the ANSI C 'strtok' function: + + The first call to fits\_split\_names has a non-null input string. + It finds the first name in the string and terminates it by overwriting + the next character of the string with a null terminator and returns a + pointer to the name. Each subsequent call, indicated by a NULL value + of the input string, returns the next name, searching from just past + the end of the previous name. It returns NULL when no further names +> are found. \label{splitnames} +- + char *fits_split_names(char *namelist) +- + The following example shows how a string would be split into 3 names: +- + myfile[1][bin (x,y)=4], file2.fits file3.fits + ^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^ ^^^^^^^^^^ + 1st name 2nd name 3rd name +- +>6 Test that the keyword name contains only legal characters (A-Z,0-9, + hyphen, and underscore) or that the keyword record contains only legal +> printable ASCII characters \label{fftkey} \label{fftrec} +- + int fits_test_keyword / fftkey (char *keyname, > int *status) + + int fits_test_record / fftrec (char *card, > int *status) +- +>7 Test whether the current header contains any NULL (ASCII 0) characters. + These characters are illegal in the header, but they will go undetected + by most of the CFITSIO keyword header routines, because the null is + interpreted as the normal end-of-string terminator. This routine returns + the position of the first null character in the header, or zero if there + are no nulls. For example a returned value of 110 would indicate that + the first NULL is located in the 30th character of the second keyword + in the header (recall that each header record is 80 characters long). + Note that this is one of the few CFITSIO routines in which the returned +> value is not necessarily equal to the status value). \label{ffnchk} +- + int fits_null_check / ffnchk (char *card, > int *status) +- +>8 Parse a header keyword record and return the name of the keyword, + and the length of the name. + The keyword name normally occupies the first 8 characters of the + record, except under the HIERARCH convention where the name can +> be up to 70 characters in length. \label{ffgknm} +- + int fits_get_keyname / ffgknm + (char *card, > char *keyname, int *keylength, int *status) +- +>9 Parse a header keyword record, returning the value (as + a literal character string) and comment strings. If the keyword has no + value (columns 9-10 not equal to '= '), then a null value string is + returned and the comment string is set equal to column 9 - 80 of the +> input string. \label{ffpsvc} +- + int fits_parse_value / ffpsvc + (char *card, > char *value, char *comment, int *status) +- +>10 Construct an array indexed keyword name (ROOT + nnn). + This routine appends the sequence number to the root string to create +> a keyword name (e.g., 'NAXIS' + 2 = 'NAXIS2') \label{ffkeyn} +- + int fits_make_keyn / ffkeyn + (char *keyroot, int value, > char *keyname, int *status) +- +>11 Construct a sequence keyword name (n + ROOT). + This routine concatenates the sequence number to the front of the +> root string to create a keyword name (e.g., 1 + 'CTYP' = '1CTYP') \label{ffnkey} +- + int fits_make_nkey / ffnkey + (int value, char *keyroot, > char *keyname, int *status) +- +>12 Determine the data type of a keyword value string. This routine + parses the keyword value string to determine its data type. + Returns 'C', 'L', 'I', 'F' or 'X', for character string, logical, +> integer, floating point, or complex, respectively. \label{ffdtyp} +- + int fits_get_keytype / ffdtyp + (char *value, > char *dtype, int *status) +- +>13 Determine the integer data type of an integer keyword value string. + The returned datatype value is the minimum integer datatype (starting + from top of the following list and working down) required +> to store the integer value: +- + Data Type Range + TSBYTE: -128 to 127 + TBYTE: 128 to 255 + TSHORT: -32768 to 32767 + TUSHORT: 32768 to 65535 + TINT -2147483648 to 2147483647 + TUINT 2147483648 to 4294967295 + TLONGLONG -9223372036854775808 to 9223372036854775807 +- +> The *neg parameter returns 1 if the input value is +> negative and returns 0 if it is non-negative.\label{ffinttyp} +- + int fits_get_inttype / ffinttyp + (char *value, > int *datatype, int *neg, int *status) +- +>14 Return the class of an input header record. The record is classified + into one of the following categories (the class values are + defined in fitsio.h). Note that this is one of the few CFITSIO +> routines that does not return a status value. \label{ffgkcl} +- + Class Value Keywords + TYP_STRUC_KEY 10 SIMPLE, BITPIX, NAXIS, NAXISn, EXTEND, BLOCKED, + GROUPS, PCOUNT, GCOUNT, END + XTENSION, TFIELDS, TTYPEn, TBCOLn, TFORMn, THEAP, + and the first 4 COMMENT keywords in the primary array + that define the FITS format. + TYP_CMPRS_KEY 20 The experimental keywords used in the compressed + image format ZIMAGE, ZCMPTYPE, ZNAMEn, ZVALn, + ZTILEn, ZBITPIX, ZNAXISn, ZSCALE, ZZERO, ZBLANK + TYP_SCAL_KEY 30 BSCALE, BZERO, TSCALn, TZEROn + TYP_NULL_KEY 40 BLANK, TNULLn + TYP_DIM_KEY 50 TDIMn + TYP_RANG_KEY 60 TLMINn, TLMAXn, TDMINn, TDMAXn, DATAMIN, DATAMAX + TYP_UNIT_KEY 70 BUNIT, TUNITn + TYP_DISP_KEY 80 TDISPn + TYP_HDUID_KEY 90 EXTNAME, EXTVER, EXTLEVEL, HDUNAME, HDUVER, HDULEVEL + TYP_CKSUM_KEY 100 CHECKSUM, DATASUM + TYP_WCS_KEY 110 WCS keywords defined in the the WCS papers, including: + CTYPEn, CUNITn, CRVALn, CRPIXn, CROTAn, CDELTn + CDj_is, PVj_ms, LONPOLEs, LATPOLEs + TCTYPn, TCTYns, TCUNIn, TCUNns, TCRVLn, TCRVns, TCRPXn, + TCRPks, TCDn_k, TCn_ks, TPVn_m, TPn_ms, TCDLTn, TCROTn + jCTYPn, jCTYns, jCUNIn, jCUNns, jCRVLn, jCRVns, iCRPXn, + iCRPns, jiCDn, jiCDns, jPVn_m, jPn_ms, jCDLTn, jCROTn + (i,j,m,n are integers, s is any letter) + TYP_REFSYS_KEY 120 EQUINOXs, EPOCH, MJD-OBSs, RADECSYS, RADESYSs, DATE-OBS + TYP_COMM_KEY 130 COMMENT, HISTORY, (blank keyword) + TYP_CONT_KEY 140 CONTINUE + TYP_USER_KEY 150 all other keywords + + int fits_get_keyclass / ffgkcl (char *card) +- +>15 Parse the 'TFORM' binary table column format string. + This routine parses the input TFORM character string and returns the + integer data type code, the repeat count of the field, and, in the case + of character string fields, the length of the unit string. See Appendix + B for the allowed values for the returned typecode parameter. A +> null pointer may be given for any output parameters that are not needed. \label{ffbnfm} +- + int fits_binary_tform / ffbnfm + (char *tform, > int *typecode, long *repeat, long *width, + int *status) + + int fits_binary_tformll / ffbnfmll + (char *tform, > int *typecode, LONGLONG *repeat, long *width, + int *status) +- +>16 Parse the 'TFORM' keyword value that defines the column format in + an ASCII table. This routine parses the input TFORM character + string and returns the data type code, the width of the column, + and (if it is a floating point column) the number of decimal places + to the right of the decimal point. The returned data type codes are + the same as for the binary table, with the following + additional rules: integer columns that are between 1 and 4 characters + wide are defined to be short integers (code = TSHORT). Wider integer + columns are defined to be regular integers (code = TLONG). Similarly, + Fixed decimal point columns (with TFORM = 'Fw.d') are defined to + be single precision reals (code = TFLOAT) if w is between 1 and 7 characters + wide, inclusive. Wider 'F' columns will return a double precision + data code (= TDOUBLE). 'Ew.d' format columns will have datacode = TFLOAT, + and 'Dw.d' format columns will have datacode = TDOUBLE. A null +> pointer may be given for any output parameters that are not needed. \label{ffasfm} +- + int fits_ascii_tform / ffasfm + (char *tform, > int *typecode, long *width, int *decimals, + int *status) +- +>17 Calculate the starting column positions and total ASCII table width + based on the input array of ASCII table TFORM values. The SPACE input + parameter defines how many blank spaces to leave between each column + (it is recommended to have one space between columns for better human +> readability). \label{ffgabc} +- + int fits_get_tbcol / ffgabc + (int tfields, char **tform, int space, > long *rowlen, + long *tbcol, int *status) +- +>18 Parse a template header record and return a formatted 80-character string + suitable for appending to (or deleting from) a FITS header file. + This routine is useful for parsing lines from an ASCII template file + and reformatting them into legal FITS header records. The formatted + string may then be passed to the fits\_write\_record, ffmcrd, or + fits\_delete\_key routines +> to append or modify a FITS header record. \label{ffgthd} +- + int fits_parse_template / ffgthd + (char *templt, > char *card, int *keytype, int *status) +- + The input templt character string generally should contain 3 tokens: + (1) the KEYNAME, (2) the VALUE, and (3) the COMMENT string. The + TEMPLATE string must adhere to the following format: + +>- The KEYNAME token must begin in columns 1-8 and be a maximum of 8 + characters long. A legal FITS keyword name may only + contain the characters A-Z, 0-9, and '-' (minus sign) and + underscore. This routine will automatically convert any lowercase + characters to uppercase in the output string. If the first 8 characters + of the template line are + blank then the remainder of the line is considered to be a FITS comment +> (with a blank keyword name). + +>- The VALUE token must be separated from the KEYNAME token by one or more + spaces and/or an '=' character. The data type of the VALUE token + (numeric, logical, or character string) is automatically determined + and the output CARD string is formatted accordingly. The value + token may be forced to be interpreted as a string (e.g. if it is a + string of numeric digits) by enclosing it in single quotes. + If the value token is a character string that contains 1 or more + embedded blank space characters or slash ('/') characters then the +> entire character string must be enclosed in single quotes. + +>- The COMMENT token is optional, but if present must be separated from +> the VALUE token by a blank space or a '/' character. + +>- One exception to the above rules is that if the first non-blank + character in the first 8 characters of the template string is a + minus sign ('-') followed + by a single token, or a single token followed by an equal sign, + then it is interpreted as the name of a keyword which is to be +> deleted from the FITS header. + +>- The second exception is that if the template string starts with + a minus sign and is followed by 2 tokens (without an equals sign between + them) then the second token + is interpreted as the new name for the keyword specified by + first token. In this case the old keyword name (first token) + is returned in characters 1-8 of the returned CARD string, and + the new keyword name (the second token) is returned in characters + 41-48 of the returned CARD string. These old and new names + may then be passed to the ffmnam routine which will change +> the keyword name. + + The keytype output parameter indicates how the returned CARD string + should be interpreted: +- + keytype interpretation + ------- ------------------------------------------------- + -2 Rename the keyword with name = the first 8 characters of CARD + to the new name given in characters 41 - 48 of CARD. + + -1 delete the keyword with this name from the FITS header. + + 0 append the CARD string to the FITS header if the + keyword does not already exist, otherwise update + the keyword value and/or comment field if is already exists. + + 1 This is a HISTORY or COMMENT keyword; append it to the header + + 2 END record; do not explicitly write it to the FITS file. +- + EXAMPLES: The following lines illustrate valid input template strings: +- + INTVAL 7 / This is an integer keyword + RVAL 34.6 / This is a floating point keyword + EVAL=-12.45E-03 / This is a floating point keyword in exponential notation + lval F / This is a boolean keyword + This is a comment keyword with a blank keyword name + SVAL1 = 'Hello world' / this is a string keyword + SVAL2 '123.5' this is also a string keyword + sval3 123+ / this is also a string keyword with the value '123+ ' + # the following template line deletes the DATE keyword + - DATE + # the following template line modifies the NAME keyword to OBJECT + - NAME OBJECT +- +>19 Translate a keyword name into a new name, based on a set of patterns. +This routine is useful for translating keywords in cases such as +adding or deleting columns in +a table, or copying a column from one table to another, or extracting +an array from a cell in a binary table column into an image extension. In +these cases, it is necessary to translate the names of the keywords associated +with the original table column(s) into the appropriate keyword name in the final +file. For example, if column 2 is deleted from a table, +then the value of 'n' in all the +TFORMn and TTYPEn keywords for columns 3 and higher must be decremented +by 1. Even more complex translations are sometimes needed to convert the +WCS keywords when extracting an image out of a table column cell into +a separate image extension. + +The user passes an array of patterns to be matched. Input pattern +number i is pattern[i][0], and output pattern number i is +pattern[i][1]. Keywords are matched against the input patterns. If a +match is found then the keyword is re-written according to the output +pattern. + +Order is important. The first match is accepted. The fastest match +will be made when templates with the same first character are grouped +together. + +Several characters have special meanings: +- + i,j - single digits, preserved in output template + n - column number of one or more digits, preserved in output template + m - generic number of one or more digits, preserved in output template + a - coordinate designator, preserved in output template + # - number of one or more digits + ? - any character + * - only allowed in first character position, to match all + keywords; only useful as last pattern in the list +- +i, j, n, and m are returned by the routine. + +For example, the input pattern "iCTYPn" will match "1CTYP5" (if n\_value +is 5); the output pattern "CTYPEi" will be re-written as "CTYPE1". +Notice that "i" is preserved. + +The following output patterns are special: + + "-" - do not copy a keyword that matches the corresponding input pattern + + "+" - copy the input unchanged + +The inrec string could be just the 8-char keyword name, or the entire +80-char header record. Characters 9 - 80 in the input string simply get +appended to the translated keyword name. + +If n\_range = 0, then only keywords with 'n' equal to n\_value will be +considered as a pattern match. If n\_range = +1, then all values of +'n' greater than or equal to n\_value will be a match, and if -1, +>then values of 'n' less than or equal to n\_value will match.\label{translatekey} +- +int fits_translate_keyword( + char *inrec, /* I - input string */ + char *outrec, /* O - output converted string, or */ + /* a null string if input does not */ + /* match any of the patterns */ + char *patterns[][2],/* I - pointer to input / output string */ + /* templates */ + int npat, /* I - number of templates passed */ + int n_value, /* I - base 'n' template value of interest */ + int n_offset, /* I - offset to be applied to the 'n' */ + /* value in the output string */ + int n_range, /* I - controls range of 'n' template */ + /* values of interest (-1,0, or +1) */ + int *pat_num, /* O - matched pattern number (0 based) or -1 */ + int *i, /* O - value of i, if any, else 0 */ + int *j, /* O - value of j, if any, else 0 */ + int *m, /* O - value of m, if any, else 0 */ + int *n, /* O - value of n, if any, else 0 */ + int *status) /* IO - error status */ +- +> Here is an example of some of the patterns used to convert the keywords associated +with an image in a cell of a table column into the keywords appropriate for +>an IMAGE extension: +- + char *patterns[][2] = {{"TSCALn", "BSCALE" }, /* Standard FITS keywords */ + {"TZEROn", "BZERO" }, + {"TUNITn", "BUNIT" }, + {"TNULLn", "BLANK" }, + {"TDMINn", "DATAMIN" }, + {"TDMAXn", "DATAMAX" }, + {"iCTYPn", "CTYPEi" }, /* Coordinate labels */ + {"iCTYna", "CTYPEia" }, + {"iCUNIn", "CUNITi" }, /* Coordinate units */ + {"iCUNna", "CUNITia" }, + {"iCRVLn", "CRVALi" }, /* WCS keywords */ + {"iCRVna", "CRVALia" }, + {"iCDLTn", "CDELTi" }, + {"iCDEna", "CDELTia" }, + {"iCRPXn", "CRPIXi" }, + {"iCRPna", "CRPIXia" }, + {"ijPCna", "PCi_ja" }, + {"ijCDna", "CDi_ja" }, + {"iVn_ma", "PVi_ma" }, + {"iSn_ma", "PSi_ma" }, + {"iCRDna", "CRDERia" }, + {"iCSYna", "CSYERia" }, + {"iCROTn", "CROTAi" }, + {"WCAXna", "WCSAXESa"}, + {"WCSNna", "WCSNAMEa"}}; +- +>20 Translate the keywords in the input HDU into the keywords that are +appropriate for the output HDU. This is a driver routine that calls +>the previously described routine. +- +int fits_translate_keywords( + fitsfile *infptr, /* I - pointer to input HDU */ + fitsfile *outfptr, /* I - pointer to output HDU */ + int firstkey, /* I - first HDU record number to start with */ + char *patterns[][2],/* I - pointer to input / output keyword templates */ + int npat, /* I - number of templates passed */ + int n_value, /* I - base 'n' template value of interest */ + int n_offset, /* I - offset to be applied to the 'n' */ + /* value in the output string */ + int n_range, /* I - controls range of 'n' template */ + /* values of interest (-1,0, or +1) */ + int *status) /* IO - error status */ +- + +>21 Parse the input string containing a list of rows or row ranges, and + return integer arrays containing the first and last row in each + range. For example, if rowlist = "3-5, 6, 8-9" then it will + return numranges = 3, rangemin = 3, 6, 8 and rangemax = 5, 6, 9. + At most, 'maxranges' number of ranges will be returned. 'maxrows' + is the maximum number of rows in the table; any rows or ranges + larger than this will be ignored. The rows must be specified in + increasing order, and the ranges must not overlap. A minus sign + may be use to specify all the rows to the upper or lower bound, so + "50-" means all the rows from 50 to the end of the table, and "-" + means all the rows in the table, from 1 - maxrows. +> \label{ffrwrg} +- + int fits_parse_range / ffrwrg(char *rowlist, LONGLONG maxrows, int maxranges, > + int *numranges, long *rangemin, long *rangemax, int *status) + + int fits_parse_rangell / ffrwrgll(char *rowlist, LONGLONG maxrows, int maxranges, > + int *numranges, LONGLONG *rangemin, LONGLONG *rangemax, int *status) +- +>22 Check that the Header fill bytes (if any) are all blank. These are the bytes + that may follow END keyword and before the beginning of data unit, + or the end of the HDU if there is no data unit. +> \label{ffchfl} +- + int ffchfl(fitsfile *fptr, > int *status) +- +>23 Check that the Data fill bytes (if any) are all zero (for IMAGE or + BINARY Table HDU) or all blanks (for ASCII table HDU). These file + bytes may be located after the last valid data byte in the HDU and + before the physical end of the HDU. +> \label{ffcdfl} +- + int ffcdfl(fitsfile *fptr, > int *status) +- +>24 Estimate the root-mean-squared (RMS) noise in an image. +These routines are mainly for use with the Hcompress image compression +algorithm. They return an estimate of the RMS noise in the background +pixels of the image. This robust algorithm (written by Richard +White, STScI) first attempts to estimate the RMS value +as 1.68 times the median of the absolute differences between successive +pixels in the image. If the median = 0, then the +algorithm falls back to computing the RMS of the difference between successive +pixels, after several N-sigma rejection cycles to remove +extreme values. The input parameters are: the array of image pixel values +(either float or short values), the number of values in the array, +the value that is used to represent null pixels (enter a very +>large number if there are no null pixels). \label{imageRMS} +- + int fits_rms_float (float fdata[], int npix, float in_null_value, + > double *rms, int *status) + int fits_rms_short (short fdata[], int npix, short in_null_value, + > double *rms, int *status) +- +>25 Was CFITSIO compiled with the -D\_REENTRANT directive +so that it may be safely used in multi-threaded environments? +The following function returns 1 if yes, 0 if no. Note, however, +that even if the -D\_REENTRANT directive was specified, this does +not guarantee that the CFITSIO routines are thread-safe, because +>some compilers may not support this feature.\label{reentrant} +- +int fits_is_reentrant(void) +- + +*VII. The CFITSIO Iterator Function + +The fits\_iterate\_data function in CFITSIO provides a unique method of +executing an arbitrary user-supplied `work' function that operates on +rows of data in FITS tables or on pixels in FITS images. Rather than +explicitly reading and writing the FITS images or columns of data, one +instead calls the CFITSIO iterator routine, passing to it the name of +the user's work function that is to be executed along with a list of +all the table columns or image arrays that are to be passed to the work +function. The CFITSIO iterator function then does all the work of +allocating memory for the arrays, reading the input data from the FITS +file, passing them to the work function, and then writing any output +data back to the FITS file after the work function exits. Because +it is often more efficient to process only a subset of the total table +rows at one time, the iterator function can determine the optimum +amount of data to pass in each iteration and repeatedly call the work +function until the entire table been processed. + +For many applications this single CFITSIO iterator function can +effectively replace all the other CFITSIO routines for reading or +writing data in FITS images or tables. Using the iterator has several +important advantages over the traditional method of reading and writing +FITS data files: + +\begin{itemize} +\item +It cleanly separates the data I/O from the routine that operates on +the data. This leads to a more modular and `object oriented' +programming style. + +\item +It simplifies the application program by eliminating the need to allocate +memory for the data arrays and eliminates most of the calls to the CFITSIO +routines that explicitly read and write the data. + +\item +It ensures that the data are processed as efficiently as possible. +This is especially important when processing tabular data since +the iterator function will calculate the most efficient number +of rows in the table to be passed at one time to the user's work +function on each iteration. + +\item +Makes it possible for larger projects to develop a library of work +functions that all have a uniform calling sequence and are all +independent of the details of the FITS file format. + +\end{itemize} + +There are basically 2 steps in using the CFITSIO iterator function. +The first step is to design the work function itself which must have a +prescribed set of input parameters. One of these parameters is a +structure containing pointers to the arrays of data; the work function +can perform any desired operations on these arrays and does not need to +worry about how the input data were read from the file or how the +output data get written back to the file. + +The second step is to design the driver routine that opens all the +necessary FITS files and initializes the input parameters to the +iterator function. The driver program calls the CFITSIO iterator +function which then reads the data and passes it to the user's work +function. + +The following 2 sections describe these steps in more detail. There +are also several example programs included with the CFITSIO +distribution which illustrate how to use the iterator function. + +**A The Iterator Work Function + +The user-supplied iterator work function must have the following set of +input parameters (the function can be given any desired name): + +- + int user_fn( long totaln, long offset, long firstn, long nvalues, + int narrays, iteratorCol *data, void *userPointer ) +- + +\begin{itemize} + +\item + totaln -- the total number of table rows or image pixels + that will be passed to the work function + during 1 or more iterations. + +\item + offset -- the offset applied to the first table row or image + pixel to be passed to the work function. In other + words, this is the number of rows or pixels that + are skipped over before starting the iterations. If + offset = 0, then all the table rows or image pixels + will be passed to the work function. + +\item + firstn -- the number of the first table row or image pixel + (starting with 1) that is being passed in this + particular call to the work function. + +\item + nvalues -- the number of table rows or image pixels that are + being passed in this particular call to the work + function. nvalues will always be less than or + equal to totaln and will have the same value on + each iteration, except possibly on the last + call which may have a smaller value. + +\item + narrays -- the number of arrays of data that are being passed + to the work function. There is one array for each + image or table column. + +\item + *data -- array of structures, one for each + column or image. Each structure contains a pointer + to the array of data as well as other descriptive + parameters about that array. + +\item + *userPointer -- a user supplied pointer that can be used + to pass ancillary information from the driver function + to the work function. + This pointer is passed to the CFITSIO iterator function + which then passes it on to the + work function without any modification. + It may point to a single number, to an array of values, + to a structure containing an arbitrary set of parameters + of different types, + or it may be a null pointer if it is not needed. + The work function must cast this pointer to the + appropriate data type before using it it. +\end{itemize} + +The totaln, offset, narrays, data, and userPointer parameters are +guaranteed to have the same value on each iteration. Only firstn, +nvalues, and the arrays of data pointed to by the data structures may +change on each iterative call to the work function. + +Note that the iterator treats an image as a long 1-D array of pixels +regardless of it's intrinsic dimensionality. The total number of +pixels is just the product of the size of each dimension, and the order +of the pixels is the same as the order that they are stored in the FITS +file. If the work function needs to know the number and size of the +image dimensions then these parameters can be passed via the +userPointer structure. + +The iteratorCol structure is currently defined as follows: +- +typedef struct /* structure for the iterator function column information */ +{ + /* structure elements required as input to fits_iterate_data: */ + + fitsfile *fptr; /* pointer to the HDU containing the column or image */ + int colnum; /* column number in the table; ignored for images */ + char colname[70]; /* name (TTYPEn) of the column; null for images */ + int datatype; /* output data type (converted if necessary) */ + int iotype; /* type: InputCol, InputOutputCol, or OutputCol */ + + /* output structure elements that may be useful for the work function: */ + + void *array; /* pointer to the array (and the null value) */ + long repeat; /* binary table vector repeat value; set */ + /* equal to 1 for images */ + long tlmin; /* legal minimum data value, if any */ + long tlmax; /* legal maximum data value, if any */ + char unit[70]; /* physical unit string (BUNIT or TUNITn) */ + char tdisp[70]; /* suggested display format; null if none */ + +} iteratorCol; +- + +Instead of directly reading or writing the elements in this structure, +it is recommended that programmers use the access functions that are +provided for this purpose. + +The first five elements in this structure must be initially defined by +the driver routine before calling the iterator routine. The CFITSIO +iterator routine uses this information to determine what column or +array to pass to the work function, and whether the array is to be +input to the work function, output from the work function, or both. +The CFITSIO iterator function fills in the values of the remaining +structure elements before passing it to the work function. + +The array structure element is a pointer to the actual data array and +it must be cast to the correct data type before it is used. The +`repeat' structure element give the number of data values in each row +of the table, so that the total number of data values in the array is +given by repeat * nvalues. In the case of image arrays and ASCII +tables, repeat will always be equal to 1. When the data type is a +character string, the array pointer is actually a pointer to an array +of string pointers (i.e., char **array). The other output structure +elements are provided for convenience in case that information is +needed within the work function. Any other information may be passed +from the driver routine to the work function via the userPointer +parameter. + +Upon completion, the work routine must return an integer status value, +with 0 indicating success and any other value indicating an error which +will cause the iterator function to immediately exit at that point. Return status +values in the range 1 -- 1000 should be avoided since these are +reserved for use by CFITSIO. A return status value of -1 may be used to +force the CFITSIO iterator function to stop at that point and return +control to the driver routine after writing any output arrays to the +FITS file. CFITSIO does not considered this to be an error condition, +so any further processing by the application program will continue normally. + +**B The Iterator Driver Function + +The iterator driver function must open the necessary FITS files and +position them to the correct HDU. It must also initialize the following +parameters in the iteratorCol structure (defined above) for each +column or image before calling the CFITSIO iterator function. +Several `constructor' routines are provided in CFITSIO for this +purpose. + +\begin{itemize} +\item + *fptr -- The fitsfile pointer to the table or image. +\item +colnum -- the number of the column in the table. This value is ignored + in the case of images. If colnum equals 0, then the column name + will be used to identify the column to be passed to the + work function. + +\item +colname -- the name (TTYPEn keyword) of the column. This is + only required if colnum = 0 and is ignored for images. +\item +datatype -- The desired data type of the array to be passed to the + work function. For numerical data the data type does + not need to be the same as the actual data type in the + FITS file, in which case CFITSIO will do the conversion. + Allowed values are: TSTRING, TLOGICAL, TBYTE, TSBYTE, TSHORT, TUSHORT, + TINT, TLONG, TULONG, TFLOAT, TDOUBLE. If the input + value of data type equals 0, then the existing + data type of the column or image will be used without + any conversion. + +\item +iotype -- defines whether the data array is to be input to the + work function (i.e, read from the FITS file), or output + from the work function (i.e., written to the FITS file) or + both. Allowed values are InputCol, OutputCol, or InputOutputCol. + Variable-length array columns are supported as InputCol or + InputOutputCol types, but may not be used for an OutputCol type. +\end{itemize} + +After the driver routine has initialized all these parameters, it +can then call the CFITSIO iterator function: + +- + int fits_iterate_data(int narrays, iteratorCol *data, long offset, + long nPerLoop, int (*workFn)( ), void *userPointer, int *status); +- + +\begin{itemize} +\item + + narrays -- the number of columns or images that are to be passed + to the work function. +\item + *data -- pointer to array of structures containing information + about each column or image. + +\item + offset -- if positive, this number of rows at the + beginning of the table (or pixels in the image) + will be skipped and will not be passed to the work + function. + +\item + nPerLoop - specifies the number of table rows (or number of + image pixels) that are to be passed to the work + function on each iteration. If nPerLoop = 0 + then CFITSIO will calculate the optimum number + for greatest efficiency. + If nPerLoop is negative, then all the rows + or pixels will be passed at one time, and the work + function will only be called once. If any variable + length arrays are being processed, then the nPerLoop + value is ignored, and the iterator will always process + one row of the table at a time. + +\item + *workFn - the name (actually the address) of the work function + that is to be called by fits\_iterate\_data. + +\item + *userPointer - this is a user supplied pointer that can be used + to pass ancillary information from the driver routine + to the work function. It may point to a single number, + an array, or to a structure containing an arbitrary set + of parameters. + +\item + *status - The CFITSIO error status. Should = 0 on input; + a non-zero output value indicates an error. +\end{itemize} + +When fits\_iterate\_data is called it first allocates memory to hold +all the requested columns of data or image pixel arrays. It then reads +the input data from the FITS tables or images into the arrays then +passes the structure with pointers to these data arrays to the work +function. After the work function returns, the iterator function +writes any output columns of data or images back to the FITS files. It +then repeats this process for any remaining sets of rows or image +pixels until it has processed the entire table or image or until the +work function returns a non-zero status value. The iterator then frees +the memory that it initially allocated and returns control to the +driver routine that called it. + +**C. Guidelines for Using the Iterator Function + +The totaln, offset, firstn, and nvalues parameters that are passed to +the work function are useful for determining how much of the data has +been processed and how much remains left to do. On the very first call +to the work function firstn will be equal to offset + 1; the work +function may need to perform various initialization tasks before +starting to process the data. Similarly, firstn + nvalues - 1 will be +equal to totaln on the last iteration, at which point the work function +may need to perform some clean up operations before exiting for the +last time. The work function can also force an early termination of +the iterations by returning a status value = -1. + +The narrays and iteratorCol.datatype arguments allow the work function +to double check that the number of input arrays and their data types +have the expected values. The iteratorCol.fptr and iteratorCol.colnum +structure elements can be used if the work function needs to read or +write the values of other keywords in the FITS file associated with +the array. This should generally only be done during the +initialization step or during the clean up step after the last set of +data has been processed. Extra FITS file I/O during the main +processing loop of the work function can seriously degrade the speed of +the program. + +If variable-length array columns are being processed, then the iterator +will operate on one row of the table at a time. In this case the +the repeat element in the interatorCol structure will be set equal to +the number of elements in the current row that is being processed. + +One important feature of the iterator is that the first element in each +array that is passed to the work function gives the value that is used +to represent null or undefined values in the array. The real data then +begins with the second element of the array (i.e., array[1], not +array[0]). If the first array element is equal to zero, then this +indicates that all the array elements have defined values and there are +no undefined values. If array[0] is not equal to zero, then this +indicates that some of the data values are undefined and this value +(array[0]) is used to represent them. In the case of output arrays +(i.e., those arrays that will be written back to the FITS file by the +iterator function after the work function exits) the work function must +set the first array element to the desired null value if necessary, +otherwise the first element should be set to zero to indicate that +there are no null values in the output array. CFITSIO defines 2 +values, FLOATNULLVALUE and DOUBLENULLVALUE, that can be used as default +null values for float and double data types, respectively. In the case +of character string data types, a null string is always used to +represent undefined strings. + +In some applications it may be necessary to recursively call the iterator +function. An example of this is given by one of the example programs +that is distributed with CFITSIO: it first calls a work function that +writes out a 2D histogram image. That work function in turn calls +another work function that reads the `X' and `Y' columns in a table to +calculate the value of each 2D histogram image pixel. Graphically, the +program structure can be described as: +- + driver --> iterator --> work1_fn --> iterator --> work2_fn +- + +Finally, it should be noted that the table columns or image arrays that +are passed to the work function do not all have to come from the same +FITS file and instead may come from any combination of sources as long +as they have the same length. The length of the first table column or +image array is used by the iterator if they do not all have the same +length. + +**D. Complete List of Iterator Routines + +All of the iterator routines are listed below. Most of these routines +do not have a corresponding short function name. + +>1 Iterator `constructor' functions that set + the value of elements in the iteratorCol structure + that define the columns or arrays. These set the fitsfile + pointer, column name, column number, datatype, and iotype, + respectively. The last 2 routines allow all the parameters + to be set with one function call (one supplies the column +> name, the other the column number). \label{ffiterset} + +- + int fits_iter_set_file(iteratorCol *col, fitsfile *fptr); + + int fits_iter_set_colname(iteratorCol *col, char *colname); + + int fits_iter_set_colnum(iteratorCol *col, int colnum); + + int fits_iter_set_datatype(iteratorCol *col, int datatype); + + int fits_iter_set_iotype(iteratorCol *col, int iotype); + + int fits_iter_set_by_name(iteratorCol *col, fitsfile *fptr, + char *colname, int datatype, int iotype); + + int fits_iter_set_by_num(iteratorCol *col, fitsfile *fptr, + int colnum, int datatype, int iotype); +- +>2 Iterator `accessor' functions that return the value of the + element in the iteratorCol structure +> that describes a particular data column or array \label{ffiterget} +- + fitsfile * fits_iter_get_file(iteratorCol *col); + + char * fits_iter_get_colname(iteratorCol *col); + + int fits_iter_get_colnum(iteratorCol *col); + + int fits_iter_get_datatype(iteratorCol *col); + + int fits_iter_get_iotype(iteratorCol *col); + + void * fits_iter_get_array(iteratorCol *col); + + long fits_iter_get_tlmin(iteratorCol *col); + + long fits_iter_get_tlmax(iteratorCol *col); + + long fits_iter_get_repeat(iteratorCol *col); + + char * fits_iter_get_tunit(iteratorCol *col); + + char * fits_iter_get_tdisp(iteratorCol *col); +- +>>3 The CFITSIO iterator function \label{ffiter} +- + int fits_iterate_data(int narrays, iteratorCol *data, long offset, + long nPerLoop, + int (*workFn)( long totaln, long offset, long firstn, + long nvalues, int narrays, iteratorCol *data, + void *userPointer), + void *userPointer, + int *status); +- + +*IX. World Coordinate System Routines + +The FITS community has adopted a set of keyword conventions that define +the transformations needed to convert between pixel locations in an +image and the corresponding celestial coordinates on the sky, or more +generally, that define world coordinates that are to be associated with +any pixel location in an n-dimensional FITS array. CFITSIO is distributed +with a a few self-contained World Coordinate System (WCS) routines, +however, these routines DO NOT support all the latest WCS conventions, +so it is STRONGLY RECOMMENDED that software developers use a more robust +external WCS library. Several recommended libraries are: + +- + WCSLIB - supported by Mark Calabretta + WCSTools - supported by Doug Mink + AST library - developed by the U.K. Starlink project +- + +More information about the WCS keyword conventions and links to all of +these WCS libraries can be found on the FITS Support Office web site at +http://fits.gsfc.nasa.gov under the WCS link. + +The functions provided in these external WCS libraries will need +access to the WCS keywords contained in the FITS file headers. +One convenient way to pass this information to the external library is +to use the fits\_hdr2str routine in CFITSIO (defined below) to copy the +header keywords into one long string, and then pass this string to an +interface routine in the external library that will extract +the necessary WCS information (e.g., the 'wcspih' routine in the WCSLIB +library and the 'astFitsChan' and 'astPutCards' functions in the AST +library). + +>1 Concatenate the header keywords in the CHDU into a single long + string of characters. Each 80-character fixed-length keyword + record is appended to the output character string, in order, with + no intervening separator or terminating characters. The last header + record is terminated with a NULL character. This routine allocates + memory for the returned character array, so the calling program must + free the memory when finished. + + There are 2 related routines: fits\_hdr2str simply concatenates all + the existing keywords in the header; fits\_convert\_hdr2str is similar, + except that if the CHDU is a tile compressed image (stored in a binary + table) then it will first convert that header back to that of a + normal FITS image before concatenating the keywords. + + Selected keywords may be excluded from the returned character string. + If the second parameter (nocomments) is TRUE (nonzero) then any + COMMENT, HISTORY, or blank keywords in the header will not be copied + to the output string. + + The 'exclist' parameter may be used to supply a list of keywords + that are to be excluded from the output character string. Wild card + characters (*, ?, and \#) may be used in the excluded keyword names. + If no additional keywords are to be excluded, then set nexc = 0 and +> specify NULL for the the **exclist parameter. \label{hdr2str} +- + int fits_hdr2str + (fitsfile *fptr, int nocomments, char **exclist, int nexc, + > char **header, int *nkeys, int *status) + + int fits_convert_hdr2str / ffcnvthdr2str + (fitsfile *fptr, int nocomments, char **exclist, int nexc, + > char **header, int *nkeys, int *status) +- + +>2 The following CFITSIO routine is specifically designed for use +in conjunction with the WCSLIB library. It is not expected that +applications programmers will call this routine directly, but it +is documented here for completeness. This routine extracts arrays +from a binary table that contain WCS information using the -TAB table +lookup convention. See the documentation provided with the WCSLIB +> library for more information. \label{wcstab} +- + int fits_read_wcstab + (fitsfile *fptr, int nwtb, wtbarr *wtb, int *status); +- +**A. Self-contained WCS Routines + +The following routines DO NOT support the more recent WCS conventions +that have been approved as part of the FITS standard. Consequently, +the following routines ARE NOW DEPRECATED. It is STRONGLY RECOMMENDED +that software developers not use these routines, and instead use an +external WCS library, as described in the previous section. + +These routines are included mainly for backward compatibility with +existing software. They support the following standard map +projections: -SIN, -TAN, -ARC, -NCP, -GLS, -MER, and -AIT (these are the +legal values for the coordtype parameter). These routines are based +on similar functions in Classic AIPS. All the angular quantities are +given in units of degrees. + +>1 Get the values of the basic set of standard FITS celestial coordinate + system keywords from the header of a FITS image (i.e., the primary + array or an IMAGE extension). These values may then be passed to + the fits\_pix\_to\_world and fits\_world\_to\_pix routines that + perform the coordinate transformations. If any or all of the WCS + keywords are not present, then default values will be returned. If + the first coordinate axis is the declination-like coordinate, then + this routine will swap them so that the longitudinal-like coordinate + is returned as the first axis. + + The first routine (ffgics) returns + the primary WCS, whereas the second routine returns the particular + version of the WCS specified by the 'version' parameter, which much + be a character ranging from 'A' to 'Z' (or a blank character, which is + equivalent to calling ffgics). + + If the file uses the newer 'CDj\_i' WCS transformation matrix + keywords instead of old style 'CDELTn' and 'CROTA2' keywords, then + this routine will calculate and return the values of the equivalent + old-style keywords. Note that the conversion from the new-style + keywords to the old-style values is sometimes only an + approximation, so if the approximation is larger than an internally + defined threshold level, then CFITSIO will still return the + approximate WCS keyword values, but will also return with status = + APPROX\_WCS\_KEY, to warn the calling program that approximations + have been made. It is then up to the calling program to decide + whether the approximations are sufficiently accurate for the + particular application, or whether more precise WCS transformations +> must be performed using new-style WCS keywords directly. \label{ffgics} +- + int fits_read_img_coord / ffgics + (fitsfile *fptr, > double *xrefval, double *yrefval, + double *xrefpix, double *yrefpix, double *xinc, double *yinc, + double *rot, char *coordtype, int *status) + + int fits_read_img_coord_version / ffgicsa + (fitsfile *fptr, char version, > double *xrefval, double *yrefval, + double *xrefpix, double *yrefpix, double *xinc, double *yinc, + double *rot, char *coordtype, int *status) +- +>2 Get the values of the standard FITS celestial coordinate system + keywords from the header of a FITS table where the X and Y (or RA + and DEC) coordinates are stored in 2 separate columns of the table + (as in the Event List table format that is often used by high energy + astrophysics missions). These values may then be passed to the + fits\_pix\_to\_world and fits\_world\_to\_pix routines that perform +> the coordinate transformations. \label{ffgtcs} +- + int fits_read_tbl_coord / ffgtcs + (fitsfile *fptr, int xcol, int ycol, > double *xrefval, + double *yrefval, double *xrefpix, double *yrefpix, double *xinc, + double *yinc, double *rot, char *coordtype, int *status) +- +>3 Calculate the celestial coordinate corresponding to the input +> X and Y pixel location in the image. \label{ffwldp} +- + int fits_pix_to_world / ffwldp + (double xpix, double ypix, double xrefval, double yrefval, + double xrefpix, double yrefpix, double xinc, double yinc, + double rot, char *coordtype, > double *xpos, double *ypos, + int *status) +- +>4 Calculate the X and Y pixel location corresponding to the input +> celestial coordinate in the image. \label{ffxypx} +- + int fits_world_to_pix / ffxypx + (double xpos, double ypos, double xrefval, double yrefval, + double xrefpix, double yrefpix, double xinc, double yinc, + double rot, char *coordtype, > double *xpix, double *ypix, + int *status) +- + + +*VIII Hierarchical Grouping Routines + +These functions allow for the creation and manipulation of FITS HDU +Groups, as defined in "A Hierarchical Grouping Convention for FITS" by +Jennings, Pence, Folk and Schlesinger: + +http://fits.gsfc.nasa.gov/group.html + +A group is a +collection of HDUs whose association is defined by a {\it grouping +table}. HDUs which are part of a group are referred to as {\it member +HDUs} or simply as {\it members}. Grouping table member HDUs may +themselves be grouping tables, thus allowing for the construction of +open-ended hierarchies of HDUs. + +Grouping tables contain one row for each member HDU. The grouping table +columns provide identification information that allows applications to +reference or "point to" the member HDUs. Member HDUs are expected, but +not required, to contain a set of GRPIDn/GRPLCn keywords in their +headers for each grouping table that they are referenced by. In this +sense, the GRPIDn/GRPLCn keywords "link" the member HDU back to its +Grouping table. Note that a member HDU need not reside in the same FITS +file as its grouping table, and that a given HDU may be referenced by +up to 999 grouping tables simultaneously. + +Grouping tables are implemented as FITS binary tables with up to six +pre-defined column TTYPEn values: 'MEMBER\_XTENSION', 'MEMBER\_NAME', +'MEMBER\_VERSION', 'MEMBER\_POSITION', 'MEMBER\_URI\_TYPE' and 'MEMBER\_LOCATION'. +The first three columns allow member HDUs to be identified by reference to +their XTENSION, EXTNAME and EXTVER keyword values. The fourth column allows +member HDUs to be identified by HDU position within their FITS file. +The last two columns identify the FITS file in which the member HDU resides, +if different from the grouping table FITS file. + +Additional user defined "auxiliary" columns may also be included with any +grouping table. When a grouping table is copied or modified the presence of +auxiliary columns is always taken into account by the grouping support +functions; however, the grouping support functions cannot directly +make use of this data. + +If a grouping table column is defined but the corresponding member HDU +information is unavailable then a null value of the appropriate data type +is inserted in the column field. Integer columns (MEMBER\_POSITION, +MEMBER\_VERSION) are defined with a TNULLn value of zero (0). Character field +columns (MEMBER\_XTENSION, MEMBER\_NAME, MEMBER\_URI\_TYPE, MEMBER\_LOCATION) +utilize an ASCII null character to denote a null field value. + +The grouping support functions belong to two basic categories: those that +work with grouping table HDUs (ffgt**) and those that work with member HDUs +(ffgm**). Two functions, fits\_copy\_group() and fits\_remove\_group(), have the +option to recursively copy/delete entire groups. Care should be taken when +employing these functions in recursive mode as poorly defined groups could +cause unpredictable results. The problem of a grouping table directly or +indirectly referencing itself (thus creating an infinite loop) is protected +against; in fact, neither function will attempt to copy or delete an HDU +twice. + +**A. Grouping Table Routines + +>1 Create (append) a grouping table at the end of the current FITS file + pointed to by fptr. The grpname parameter provides the grouping table + name (GRPNAME keyword value) and may be set to NULL if no group name + is to be specified. The grouptype parameter specifies the desired + structure of the grouping table and may take on the values: + GT\_ID\_ALL\_URI (all columns created), GT\_ID\_REF (ID by reference columns), + GT\_ID\_POS (ID by position columns), GT\_ID\_ALL (ID by reference and + position columns), GT\_ID\_REF\_URI (ID by reference and FITS file URI +> columns), and GT\_ID\_POS\_URI (ID by position and FITS file URI columns). \label{ffgtcr} +- + int fits_create_group / ffgtcr + (fitsfile *fptr, char *grpname, int grouptype, > int *status) +- +>2 Create (insert) a grouping table just after the CHDU of the current FITS + file pointed to by fptr. All HDUs below the the insertion point will be + shifted downwards to make room for the new HDU. The grpname parameter + provides the grouping table name (GRPNAME keyword value) and may be set to + NULL if no group name is to be specified. The grouptype parameter specifies + the desired structure of the grouping table and may take on the values: + GT\_ID\_ALL\_URI (all columns created), GT\_ID\_REF (ID by reference columns), + GT\_ID\_POS (ID by position columns), GT\_ID\_ALL (ID by reference and + position columns), GT\_ID\_REF\_URI (ID by reference and FITS file URI +> columns), and GT\_ID\_POS\_URI (ID by position and FITS file URI columns) \label{ffgtis}. +- + int fits_insert_group / ffgtis + (fitsfile *fptr, char *grpname, int grouptype, > int *status) +- +>3 Change the structure of an existing grouping table pointed to by + gfptr. The grouptype parameter (see fits\_create\_group() for valid + parameter values) specifies the new structure of the grouping table. This + function only adds or removes grouping table columns, it does not add + or delete group members (i.e., table rows). If the grouping table already + has the desired structure then no operations are performed and function + simply returns with a (0) success status code. If the requested structure + change creates new grouping table columns, then the column values for all + existing members will be filled with the null values appropriate to the +> column type. \label{ffgtch} +- + int fits_change_group / ffgtch + (fitsfile *gfptr, int grouptype, > int *status) +- +>4 Remove the group defined by the grouping table pointed to by gfptr, and + optionally all the group member HDUs. The rmopt parameter specifies the + action to be taken for + all members of the group defined by the grouping table. Valid values are: + OPT\_RM\_GPT (delete only the grouping table) and OPT\_RM\_ALL (recursively + delete all HDUs that belong to the group). Any groups containing the + grouping table gfptr as a member are updated, and if rmopt == OPT\_RM\_GPT + all members have their GRPIDn and GRPLCn keywords updated accordingly. + If rmopt == OPT\_RM\_ALL, then other groups that contain the deleted members +> of gfptr are updated to reflect the deletion accordingly. \label{ffgtrm} +- + int fits_remove_group / ffgtrm + (fitsfile *gfptr, int rmopt, > int *status) +- +>5 Copy (append) the group defined by the grouping table pointed to by infptr, + and optionally all group member HDUs, to the FITS file pointed to by + outfptr. The cpopt parameter specifies the action to be taken for all + members of the group infptr. Valid values are: OPT\_GCP\_GPT (copy only + the grouping table) and OPT\_GCP\_ALL (recursively copy ALL the HDUs that + belong to the group defined by infptr). If the cpopt == OPT\_GCP\_GPT then + the members of infptr have their GRPIDn and GRPLCn keywords updated to + reflect the existence of the new grouping table outfptr, since they now + belong to the new group. If cpopt == OPT\_GCP\_ALL then the new + grouping table outfptr only contains pointers to the copied member HDUs + and not the original member HDUs of infptr. Note that, when + cpopt == OPT\_GCP\_ALL, all members of the group defined by infptr will be + copied to a single FITS file pointed to by outfptr regardless of their +> file distribution in the original group. \label{ffgtcp} +- + int fits_copy_group / ffgtcp + (fitsfile *infptr, fitsfile *outfptr, int cpopt, > int *status) +- +>6 Merge the two groups defined by the grouping table HDUs infptr and outfptr + by combining their members into a single grouping table. All member HDUs + (rows) are copied from infptr to outfptr. If mgopt == OPT\_MRG\_COPY then + infptr continues to exist unaltered after the merge. If the mgopt == + OPT\_MRG\_MOV then infptr is deleted after the merge. In both cases, +> the GRPIDn and GRPLCn keywords of the member HDUs are updated accordingly. \label{ffgtmg} +- + int fits_merge_groups / ffgtmg + (fitsfile *infptr, fitsfile *outfptr, int mgopt, > int *status) +- +>7 "Compact" the group defined by grouping table pointed to by gfptr. The + compaction is achieved by merging (via fits\_merge\_groups()) all direct + member HDUs of gfptr that are themselves grouping tables. The cmopt + parameter defines whether the merged grouping table HDUs remain after + merging (cmopt == OPT\_CMT\_MBR) or if they are deleted after merging + (cmopt == OPT\_CMT\_MBR\_DEL). If the grouping table contains no direct + member HDUs that are themselves grouping tables then this function + does nothing. Note that this function is not recursive, i.e., only the +> direct member HDUs of gfptr are considered for merging. \label{ffgtcm} +- + int fits_compact_group / ffgtcm + (fitsfile *gfptr, int cmopt, > int *status) +- +>8 Verify the integrity of the grouping table pointed to by gfptr to make + sure that all group members are accessible and that all links to other + grouping tables are valid. The firstfailed parameter returns the member + ID (row number) of the first member HDU to fail verification (if positive + value) or the first group link to fail (if negative value). If gfptr is +> successfully verified then firstfailed contains a return value of 0. \label{ffgtvf} +- + int fits_verify_group / ffgtvf + (fitsfile *gfptr, > long *firstfailed, int *status) +- +>9 Open a grouping table that contains the member HDU pointed to by mfptr. + The grouping table to open is defined by the grpid parameter, which + contains the keyword index value of the GRPIDn/GRPLCn keyword(s) that + link the member HDU mfptr to the grouping table. If the grouping table + resides in a file other than the member HDUs file then an attempt is + first made to open the file readwrite, and failing that readonly. A + pointer to the opened grouping table HDU is returned in gfptr. + + Note that it is possible, although unlikely and undesirable, for the + GRPIDn/GRPLCn keywords in a member HDU header to be non-continuous, e.g., + GRPID1, GRPID2, GRPID5, GRPID6. In such cases, the grpid index value + specified in the function call shall identify the (grpid)th GRPID value. + In the above example, if grpid == 3, then the group specified by GRPID5 +> would be opened. \label{ffgtop} +- + int fits_open_group / ffgtop + (fitsfile *mfptr, int group, > fitsfile **gfptr, int *status) +- +>10 Add a member HDU to an existing grouping table pointed to by gfptr. + The member HDU may either be pointed to mfptr (which must be positioned + to the member HDU) or, if mfptr == NULL, identified by the hdupos parameter + (the HDU position number, Primary array == 1) if both the grouping table + and the member HDU reside in the same FITS file. The new member HDU shall + have the appropriate GRPIDn and GRPLCn keywords created in its header. + Note that if the member HDU is already a member of the group then it will +> not be added a second time. \label{ffgtam} +- + int fits_add_group_member / ffgtam + (fitsfile *gfptr, fitsfile *mfptr, int hdupos, > int *status) +- + +**B. Group Member Routines + +>1 Return the number of member HDUs in a grouping table gfptr. The number + member HDUs is just the NAXIS2 value (number of rows) of the grouping +> table. \label{ffgtnm} +- + int fits_get_num_members / ffgtnm + (fitsfile *gfptr, > long *nmembers, int *status) +- +>2 Return the number of groups to which the HDU pointed to by mfptr is + linked, as defined by the number of GRPIDn/GRPLCn keyword records that + appear in its header. Note that each time this function is called, the + indices of the GRPIDn/GRPLCn keywords are checked to make sure they + are continuous (ie no gaps) and are re-enumerated to eliminate gaps if +> found. \label{ffgmng} +- + int fits_get_num_groups / ffgmng + (fitsfile *mfptr, > long *nmembers, int *status) +- +>3 Open a member of the grouping table pointed to by gfptr. The member to + open is identified by its row number within the grouping table as given + by the parameter 'member' (first member == 1) . A fitsfile pointer to + the opened member HDU is returned as mfptr. Note that if the member HDU + resides in a FITS file different from the grouping table HDU then the +> member file is first opened readwrite and, failing this, opened readonly. \label{ffgmop} +- + int fits_open_member / ffgmop + (fitsfile *gfptr, long member, > fitsfile **mfptr, int *status) +- +>4 Copy (append) a member HDU of the grouping table pointed to by gfptr. + The member HDU is identified by its row number within the grouping table + as given by the parameter 'member' (first member == 1). The copy of the + group member HDU will be appended to the FITS file pointed to by mfptr, + and upon return mfptr shall point to the copied member HDU. The cpopt + parameter may take on the following values: OPT\_MCP\_ADD which adds a new + entry in gfptr for the copied member HDU, OPT\_MCP\_NADD which does not add + an entry in gfptr for the copied member, and OPT\_MCP\_REPL which replaces +> the original member entry with the copied member entry. \label{ffgmcp} +- + int fits_copy_member / ffgmcp + (fitsfile *gfptr, fitsfile *mfptr, long member, int cpopt, > int *status) +- +>5 Transfer a group member HDU from the grouping table pointed to by + infptr to the grouping table pointed to by outfptr. The member HDU to + transfer is identified by its row number within infptr as specified by + the parameter 'member' (first member == 1). If tfopt == OPT\_MCP\_ADD then + the member HDU is made + a member of outfptr and remains a member of infptr. If tfopt == OPT\_MCP\_MOV +> then the member HDU is deleted from infptr after the transfer to outfptr. \label{ffgmtf} +- + int fits_transfer_member / ffgmtf + (fitsfile *infptr, fitsfile *outfptr, long member, int tfopt, + > int *status) +- +>6 Remove a member HDU from the grouping table pointed to by gfptr. The + member HDU to be deleted is identified by its row number in the grouping + table as specified by the parameter 'member' (first member == 1). The rmopt + parameter may take on the following values: OPT\_RM\_ENTRY which + removes the member HDU entry from the grouping table and updates the + member's GRPIDn/GRPLCn keywords, and OPT\_RM\_MBR which removes the member +> HDU entry from the grouping table and deletes the member HDU itself. \label{ffgmrm} +- + int fits_remove_member / ffgmrm + (fitsfile *fptr, long member, int rmopt, > int *status) +- + +*IX Specialized CFITSIO Interface Routines + +The basic interface routines described previously are recommended +for most uses, but the routines described in this chapter +are also available if necessary. Some of these routines perform more +specialized function that cannot easily be done with the basic +interface routines while others duplicate the functionality of the +basic routines but have a slightly different calling sequence. +See Appendix B for the definition of each function parameter. + +**A. FITS File Access Routines + +>1 Open an existing FITS file residing in core computer memory. This +routine is analogous to fits\_open\_file. The 'filename' is +currently ignored by this routine and may be any arbitrary string. In +general, the application must have preallocated an initial block of +memory to hold the FITS file prior to calling this routine: 'memptr' +points to the starting address and 'memsize' gives the initial size of +the block of memory. 'mem\_realloc' is a pointer to an optional +function that CFITSIO can call to allocate additional memory, if needed +(only if mode = READWRITE), and is modeled after the standard C +'realloc' function; a null pointer may be given if the initial +allocation of memory is all that will be required (e.g., if the file is +opened with mode = READONLY). The 'deltasize' parameter may be used to +suggest a minimum amount of additional memory that should be allocated +during each call to the memory reallocation function. By default, +CFITSIO will reallocate enough additional space to hold the entire +currently defined FITS file (as given by the NAXISn keywords) or 1 FITS +block (= 2880 bytes), which ever is larger. Values of deltasize less +than 2880 will be ignored. Since the memory reallocation operation can +be computationally expensive, allocating a larger initial block of +memory, and/or specifying a larger deltasize value may help to reduce +the number of reallocation calls and make the application program run +faster. Note that values of the memptr and memsize pointers will be updated +by CFITSIO if the location or size of the FITS file in memory +>should change as a result of allocating more memory. \label{ffomem} +- + int fits_open_memfile / ffomem + (fitsfile **fptr, const char *filename, int mode, void **memptr, + size_t *memsize, size_t deltasize, + void *(*mem_realloc)(void *p, size_t newsize), int *status) +- +>2 Create a new FITS file residing in core computer memory. This +routine is analogous to fits\_create\_file. In general, the +application must have preallocated an initial block of memory to hold +the FITS file prior to calling this routine: 'memptr' points to the +starting address and 'memsize' gives the initial size of the block of +memory. 'mem\_realloc' is a pointer to an optional function that +CFITSIO can call to allocate additional memory, if needed, and is +modeled after the standard C 'realloc' function; a null pointer may be +given if the initial allocation of memory is all that will be +required. The 'deltasize' parameter may be used to suggest a minimum +amount of additional memory that should be allocated during each call +to the memory reallocation function. By default, CFITSIO will +reallocate enough additional space to hold 1 FITS block (= 2880 bytes) +and values of deltasize less than 2880 will be ignored. Since the +memory reallocation operation can be computationally expensive, +allocating a larger initial block of memory, and/or specifying a larger +deltasize value may help to reduce the number of reallocation calls +and make the application program run +faster. Note that values of the memptr and memsize pointers will be updated +by CFITSIO if the location or size of the FITS file in memory +>should change as a result of allocating more memory. \label{ffimem} +- + int fits_create_memfile / ffimem + (fitsfile **fptr, void **memptr, + size_t *memsize, size_t deltasize, + void *(*mem_realloc)(void *p, size_t newsize), int *status) +- +>3 Reopen a FITS file that was previously opened with + fits\_open\_file or fits\_create\_file. The new fitsfile + pointer may then be treated as a separate file, and one may + simultaneously read or write to 2 (or more) different extensions in + the same file. The fits\_open\_file routine (above) automatically + detects cases where a previously opened file is being opened again, + and then internally call fits\_reopen\_file, so programs should rarely + need to explicitly call this routine. +>\label{ffreopen} +- + int fits_reopen_file / ffreopen + (fitsfile *openfptr, fitsfile **newfptr, > int *status) +- + +>4 Create a new FITS file, using a template file to define its + initial size and structure. The template may be another FITS HDU + or an ASCII template file. If the input template file name pointer + is null, then this routine behaves the same as fits\_create\_file. + The currently supported format of the ASCII template file is described + under the fits\_parse\_template routine (in the general Utilities + section) +>\label{fftplt} +- + int fits_create_template / fftplt + (fitsfile **fptr, char *filename, char *tpltfile > int *status) +- + +>5 Parse the input filename or URL into its component parts, namely: +\begin{itemize} +\item +the file type (file://, ftp://, http://, etc), +\item +the base input file name, +\item +the name of the output file that the input file is to be copied to prior +to opening, +\item +the HDU or extension specification, +\item +the filtering specifier, +\item +the binning specifier, +\item +the column specifier, +\item +and the +image pixel filtering specifier. +\end{itemize} +A null pointer (0) may be be specified for any of the output string arguments +that are not needed. Null strings will be returned for any components that are not +present in the input file name. The calling routine must allocate sufficient +memory to hold the returned character strings. Allocating the string lengths +equal to FLEN\_FILENAME is guaranteed to be safe. +These routines are mainly for internal use +>by other CFITSIO routines. \label{ffiurl} +- + int fits_parse_input_url / ffiurl + (char *filename, > char *filetype, char *infile, char *outfile, char + *extspec, char *filter, char *binspec, char *colspec, int *status) + + int fits_parse_input_filename / ffifile + (char *filename, > char *filetype, char *infile, char *outfile, char + *extspec, char *filter, char *binspec, char *colspec, char *pixspec, + int *status) +- +>6 Parse the input filename and return the HDU number that would be +moved to if the file were opened with fits\_open\_file. The returned +HDU number begins with 1 for the primary array, so for example, if the +input filename = `myfile.fits[2]' then hdunum = 3 will be returned. +CFITSIO does not open the file to check if the extension actually +exists if an extension number is specified. If an extension name is +included in the file name specification (e.g. `myfile.fits[EVENTS]' +then this routine will have to open the FITS file and look for the +position of the named extension, then close file again. This is not +possible if the file is being read from the stdin stream, and an error +will be returned in this case. If the filename does not specify an +explicit extension (e.g. 'myfile.fits') then hdunum = -99 will be +returned, which is functionally equivalent to hdunum = 1. This routine +is mainly used for backward compatibility in the ftools software +package and is not recommended for general use. It is generally better +and more efficient to first open the FITS file with fits\_open\_file, +then use fits\_get\_hdu\_num to determine which HDU in the file has +been opened, rather than calling fits\_parse\_input\_url followed by a +call to fits\_open\_file. +> \label{ffextn} +- + int fits_parse_extnum / ffextn + (char *filename, > int *hdunum, int *status) +- +>7 Parse the input file name and return the root file name. The root +name includes the file type if specified, (e.g. 'ftp://' or 'http://') +and the full path name, to the extent that it is specified in the input +filename. It does not include the HDU name or number, or any filtering +specifications. The calling routine must allocate sufficient +memory to hold the returned rootname character string. Allocating the length +equal to FLEN\_FILENAME is guaranteed to be safe. +> \label{ffrtnm} +- + int fits_parse_rootname / ffrtnm + (char *filename, > char *rootname, int *status); +- +>8 Test if the input file or a compressed version of the file (with +a .gz, .Z, .z, or .zip extension) exists on disk. The returned value of +the 'exists' parameter will have 1 of the 4 following values: +- + 2: the file does not exist, but a compressed version does exist + 1: the disk file does exist + 0: neither the file nor a compressed version of the file exist + -1: the input file name is not a disk file (could be a ftp, http, + smem, or mem file, or a file piped in on the STDIN stream) +- + +> \label{ffexist} +- + int fits_file_exists / ffexist + (char *filename, > int *exists, int *status); +- +>9 Flush any internal buffers of data to the output FITS file. These + routines rarely need to be called, but can be useful in cases where + other processes need to access the same FITS file in real time, + either on disk or in memory. These routines also help to ensure + that if the application program subsequently aborts then the FITS + file will have been closed properly. The first routine, + fits\_flush\_file is more rigorous and completely closes, then + reopens, the current HDU, before flushing the internal buffers, thus + ensuring that the output FITS file is identical to what would be + produced if the FITS was closed at that point (i.e., with a call to + fits\_close\_file). The second routine, fits\_flush\_buffer simply + flushes the internal CFITSIO buffers of data to the output FITS + file, without updating and closing the current HDU. This is much + faster, but there may be circumstances where the flushed file does + not completely reflect the final state of the file as it will exist + when the file is actually closed. + + A typical use of these routines would be to flush the state of a + FITS table to disk after each row of the table is written. It is + recommend that fits\_flush\_file be called after the first row is + written, then fits\_flush\_buffer may be called after each + subsequent row is written. Note that this latter routine will not + automatically update the NAXIS2 keyword which records the number of + rows of data in the table, so this keyword must be explicitly + updated by the application program after each row is written. +> \label{ffflus} +- + int fits_flush_file / ffflus + (fitsfile *fptr, > int *status) + + int fits_flush_buffer / ffflsh + (fitsfile *fptr, 0, > int *status) + + (Note: The second argument must be 0). +- + +**B. HDU Access Routines + +>1 Get the byte offsets in the FITS file to the start of the header + and the start and end of the data in the CHDU. The difference + between headstart and dataend equals the size of the CHDU. If the + CHDU is the last HDU in the file, then dataend is also equal to the + size of the entire FITS file. Null pointers may be input for any +> of the address parameters if their values are not needed. \label{ffghad} +- + int fits_get_hduaddr / ffghad (only supports files up to 2.1 GB in size) + (fitsfile *fptr, > long *headstart, long *datastart, long *dataend, + int *status) + + int fits_get_hduaddrll / ffghadll (supports large files) + (fitsfile *fptr, > LONGLONG *headstart, LONGLONG *datastart, + LONGLONG *dataend, int *status) +- +>2 Create (append) a new empty HDU at the end of the FITS file. + This is now the CHDU but it is completely empty and has + no header keywords. It is recommended that fits\_create\_img or +> fits\_create\_tbl be used instead of this routine. \label{ffcrhd} +- + int fits_create_hdu / ffcrhd + (fitsfile *fptr, > int *status) +- +>3 Insert a new IMAGE extension immediately following the CHDU, or + insert a new Primary Array at the beginning of the file. Any + following extensions in the file will be shifted down to make room + for the new extension. If the CHDU is the last HDU in the file + then the new image extension will simply be appended to the end of + the file. One can force a new primary array to be inserted at the + beginning of the FITS file by setting status = PREPEND\_PRIMARY prior + to calling the routine. In this case the old primary array will be + converted to an IMAGE extension. The new extension (or primary + array) will become the CHDU. Refer to Chapter 9 for a list of +> pre-defined bitpix values. \label{ffiimg} +- + int fits_insert_img / ffiimg + (fitsfile *fptr, int bitpix, int naxis, long *naxes, > int *status) + + int fits_insert_imgll / ffiimgll + (fitsfile *fptr, int bitpix, int naxis, LONGLONG *naxes, > int *status) +- +>4 Insert a new ASCII or binary table extension immediately following the CHDU. + Any following extensions will be shifted down to make room for the + new extension. If there are no other following extensions then the + new table extension will simply be appended to the end of the + file. If the FITS file is currently empty then this routine will + create a dummy primary array before appending the table to it. The + new extension will become the CHDU. The tunit and extname + parameters are optional and a null pointer may be given if they are + not defined. When inserting an ASCII table with + fits\_insert\_atbl, a null pointer may given for the *tbcol + parameter in which case each column of the table will be separated + by a single space character. Similarly, if the input value of + rowlen is 0, then CFITSIO will calculate the default rowlength + based on the tbcol and ttype values. Under normal circumstances, + the nrows + paramenter should have a value of 0; CFITSIO will automatically update + the number of rows as data is written to the table. When inserting a binary table + with fits\_insert\_btbl, if there are following extensions in the + file and if the table contains variable length array columns then + pcount must specify the expected final size of the data heap, +> otherwise pcount must = 0. \label{ffitab} \label{ffibin} +- + int fits_insert_atbl / ffitab + (fitsfile *fptr, LONGLONG rowlen, LONGLONG nrows, int tfields, char *ttype[], + long *tbcol, char *tform[], char *tunit[], char *extname, > int *status) + + int fits_insert_btbl / ffibin + (fitsfile *fptr, LONGLONG nrows, int tfields, char **ttype, + char **tform, char **tunit, char *extname, long pcount, > int *status) +- +>5 Modify the size, dimensions, and/or data type of the current + primary array or image extension. If the new image, as specified + by the input arguments, is larger than the current existing image + in the FITS file then zero fill data will be inserted at the end + of the current image and any following extensions will be moved + further back in the file. Similarly, if the new image is + smaller than the current image then any following extensions + will be shifted up towards the beginning of the FITS file + and the image data will be truncated to the new size. + This routine rewrites the BITPIX, NAXIS, and NAXISn keywords +> with the appropriate values for the new image. \label{ffrsim} +- + int fits_resize_img / ffrsim + (fitsfile *fptr, int bitpix, int naxis, long *naxes, > int *status) + + int fits_resize_imgll / ffrsimll + (fitsfile *fptr, int bitpix, int naxis, LONGLONG *naxes, > int *status) +- +>6 Copy the data (and not the header) from the CHDU associated with infptr + to the CHDU associated with outfptr. This will overwrite any data + previously in the output CHDU. This low level routine is used by + fits\_copy\_hdu, but it may also be useful in certain application programs + that want to copy the data from one FITS file to another but also + want to modify the header keywords. The required FITS header keywords + which define the structure of the HDU must be written to the +> output CHDU before calling this routine. \label{ffcpdt} +- + int fits_copy_data / ffcpdt + (fitsfile *infptr, fitsfile *outfptr, > int *status) +- +>7 Read or write a specified number of bytes starting at the specified byte + offset from the start of the extension data unit. These low + level routine are intended mainly for accessing the data in + non-standard, conforming extensions, and should not be used for standard +> IMAGE, TABLE, or BINTABLE extensions. \label{ffgextn} +- + int fits_read_ext / ffgextn + (fitsfile *fptr, LONGLONG offset, LONGLONG nbytes, void *buffer) + int fits_write_ext / ffpextn + (fitsfile *fptr, LONGLONG offset, LONGLONG nbytes, void *buffer) +- +>8 This routine forces CFITSIO to rescan the current header keywords that + define the structure of the HDU (such as the NAXIS and BITPIX + keywords) so that it reinitializes the internal buffers that + describe the HDU structure. This routine is useful for + reinitializing the structure of an HDU if any of the required + keywords (e.g., NAXISn) have been modified. In practice it should + rarely be necessary to call this routine because CFITSIO +> internally calls it in most situations. \label{ffrdef} +- + int fits_set_hdustruc / ffrdef + (fitsfile *fptr, > int *status) (DEPRECATED) +- +**C. Specialized Header Keyword Routines + +***1. Header Information Routines + +>1 Reserve space in the CHU for MOREKEYS more header keywords. + This routine may be called to allocate space for additional keywords + at the time the header is created (prior to writing any data). + CFITSIO can dynamically add more space to the header when needed, + however it is more efficient to preallocate the required space +> if the size is known in advance. \label{ffhdef} +- + int fits_set_hdrsize / ffhdef + (fitsfile *fptr, int morekeys, > int *status) +- +>2 Return the number of keywords in the header (not counting the END + keyword) and the current position + in the header. The position is the number of the keyword record that + will be read next (or one greater than the position of the last keyword + that was read). A value of 1 is returned if the pointer is +> positioned at the beginning of the header. \label{ffghps} +- + int fits_get_hdrpos / ffghps + (fitsfile *fptr, > int *keysexist, int *keynum, int *status) +- + +***2. Read and Write the Required Keywords + +>1 Write the required extension header keywords into the CHU. + These routines are not required, and instead the appropriate + header may be constructed by writing each individual keyword in the + proper sequence. + + The simpler fits\_write\_imghdr routine is equivalent to calling + fits\_write\_grphdr with the default values of simple = TRUE, pcount + = 0, gcount = 1, and extend = TRUE. The PCOUNT, GCOUNT and EXTEND + keywords are not required in the primary header and are only written + if pcount is not equal to zero, gcount is not equal to zero or one, + and if extend is TRUE, respectively. When writing to an IMAGE + extension, the SIMPLE and EXTEND parameters are ignored. It is + recommended that fits\_create\_image or fits\_create\_tbl be used + instead of these routines to write the + required header keywords. The general fits\_write\_exthdr routine + may be used to write the header of any conforming FITS +> extension. \label{ffphpr} \label{ffphps} +- + int fits_write_imghdr / ffphps + (fitsfile *fptr, int bitpix, int naxis, long *naxes, > int *status) + + int fits_write_imghdrll / ffphpsll + (fitsfile *fptr, int bitpix, int naxis, LONGLONG *naxes, > int *status) + + int fits_write_grphdr / ffphpr + (fitsfile *fptr, int simple, int bitpix, int naxis, long *naxes, + LONGLONG pcount, LONGLONG gcount, int extend, > int *status) + + int fits_write_grphdrll / ffphprll + (fitsfile *fptr, int simple, int bitpix, int naxis, LONGLONG *naxes, + LONGLONG pcount, LONGLONG gcount, int extend, > int *status) + + int fits_write_exthdr /ffphext + (fitsfile *fptr, char *xtension, int bitpix, int naxis, long *naxes, + LONGLONG pcount, LONGLONG gcount, > int *status) + +- +>2 Write the ASCII table header keywords into the CHU. The optional + TUNITn and EXTNAME keywords are written only if the input pointers + are not null. A null pointer may given for the + *tbcol parameter in which case a single space will be inserted + between each column of the table. Similarly, if rowlen is + given = 0, then CFITSIO will calculate the default rowlength based on +> the tbcol and ttype values. \label{ffphtb} +- + int fits_write_atblhdr / ffphtb + (fitsfile *fptr, LONGLONG rowlen, LONGLONG nrows, int tfields, char **ttype, + long *tbcol, char **tform, char **tunit, char *extname, > int *status) +- +>3 Write the binary table header keywords into the CHU. The optional + TUNITn and EXTNAME keywords are written only if the input pointers + are not null. The pcount parameter, which specifies the + size of the variable length array heap, should initially = 0; + CFITSIO will automatically update the PCOUNT keyword value if any + variable length array data is written to the heap. The TFORM keyword + value for variable length vector columns should have the form 'Pt(len)' + or '1Pt(len)' where `t' is the data type code letter (A,I,J,E,D, etc.) + and `len' is an integer specifying the maximum length of the vectors + in that column (len must be greater than or equal to the longest + vector in the column). If `len' is not specified when the table is + created (e.g., the input TFORMn value is just '1Pt') then CFITSIO will + scan the column when the table is first closed and will append the + maximum length to the TFORM keyword value. Note that if the table + is subsequently modified to increase the maximum length of the vectors + then the modifying program is responsible for also updating the TFORM +> keyword value. \label{ffphbn} +- + int fits_write_btblhdr / ffphbn + (fitsfile *fptr, LONGLONG nrows, int tfields, char **ttype, + char **tform, char **tunit, char *extname, LONGLONG pcount, > int *status) +- +>4 Read the required keywords from the CHDU (image or table). When + reading from an IMAGE extension the SIMPLE and EXTEND parameters are + ignored. A null pointer may be supplied for any of the returned +> parameters that are not needed. \label{ffghpr} \label{ffghtb} \label{ffghbn} +- + int fits_read_imghdr / ffghpr + (fitsfile *fptr, int maxdim, > int *simple, int *bitpix, int *naxis, + long *naxes, long *pcount, long *gcount, int *extend, int *status) + + int fits_read_imghdrll / ffghprll + (fitsfile *fptr, int maxdim, > int *simple, int *bitpix, int *naxis, + LONGLONG *naxes, long *pcount, long *gcount, int *extend, int *status) + + int fits_read_atblhdr / ffghtb + (fitsfile *fptr,int maxdim, > long *rowlen, long *nrows, + int *tfields, char **ttype, LONGLONG *tbcol, char **tform, char **tunit, + char *extname, int *status) + + int fits_read_atblhdrll / ffghtbll + (fitsfile *fptr,int maxdim, > LONGLONG *rowlen, LONGLONG *nrows, + int *tfields, char **ttype, long *tbcol, char **tform, char **tunit, + char *extname, int *status) + + int fits_read_btblhdr / ffghbn + (fitsfile *fptr, int maxdim, > long *nrows, int *tfields, + char **ttype, char **tform, char **tunit, char *extname, + long *pcount, int *status) + + int fits_read_btblhdrll / ffghbnll + (fitsfile *fptr, int maxdim, > LONGLONG *nrows, int *tfields, + char **ttype, char **tform, char **tunit, char *extname, + long *pcount, int *status) +- +***3. Write Keyword Routines + +These routines simply append a new keyword to the header and do not +check to see if a keyword with the same name already exists. In +general it is preferable to use the fits\_update\_key routine to ensure +that the same keyword is not written more than once to the header. See +Appendix B for the definition of the parameters used in these +routines. + + +>1 Write (append) a new keyword of the appropriate data type into the CHU. + A null pointer may be entered for the comment parameter, which + will cause the comment field of the keyword to be left blank. The + flt, dbl, cmp, and dblcmp versions of this routine have the added + feature that if the 'decimals' parameter is negative, then the 'G' + display format rather then the 'E' format will be used when + constructing the keyword value, taking the absolute value of + 'decimals' for the precision. This will suppress trailing zeros, + and will use a fixed format rather than an exponential format, +> depending on the magnitude of the value. \label{ffpkyx} +- + int fits_write_key_str / ffpkys + (fitsfile *fptr, char *keyname, char *value, char *comment, + > int *status) + + int fits_write_key_[log, lng] / ffpky[lj] + (fitsfile *fptr, char *keyname, DTYPE numval, char *comment, + > int *status) + + int fits_write_key_[flt, dbl, fixflg, fixdbl] / ffpky[edfg] + (fitsfile *fptr, char *keyname, DTYPE numval, int decimals, + char *comment, > int *status) + + int fits_write_key_[cmp, dblcmp, fixcmp, fixdblcmp] / ffpk[yc,ym,fc,fm] + (fitsfile *fptr, char *keyname, DTYPE *numval, int decimals, + char *comment, > int *status) +- +>2 Write (append) a string valued keyword into the CHU which may be longer + than 68 characters in length. This uses the Long String Keyword + convention that is described in the`Local FITS Conventions' section + in Chapter 4. Since this uses a non-standard FITS convention to + encode the long keyword string, programs which use this routine + should also call the fits\_write\_key\_longwarn routine to add some + COMMENT keywords to warn users of the FITS file that this + convention is being used. The fits\_write\_key\_longwarn routine + also writes a keyword called LONGSTRN to record the version of the + longstring convention that has been used, in case a new convention + is adopted at some point in the future. If the LONGSTRN keyword + is already present in the header, then fits\_write\_key\_longwarn + will +> simply return without doing anything. \label{ffpkls} \label{ffplsw} +- + int fits_write_key_longstr / ffpkls + (fitsfile *fptr, char *keyname, char *longstr, char *comment, + > int *status) + + int fits_write_key_longwarn / ffplsw + (fitsfile *fptr, > int *status) +- +>3 Write (append) a numbered sequence of keywords into the CHU. The + starting index number (nstart) must be greater than 0. One may + append the same comment to every keyword (and eliminate the need + to have an array of identical comment strings, one for each keyword) by + including the ampersand character as the last non-blank character in the + (first) COMMENTS string parameter. This same string + will then be used for the comment field in all the keywords. + One may also enter a null pointer for the comment parameter to +> leave the comment field of the keyword blank. \label{ffpknx} +- + int fits_write_keys_str / ffpkns + (fitsfile *fptr, char *keyroot, int nstart, int nkeys, + char **value, char **comment, > int *status) + + int fits_write_keys_[log, lng] / ffpkn[lj] + (fitsfile *fptr, char *keyroot, int nstart, int nkeys, + DTYPE *numval, char **comment, int *status) + + int fits_write_keys_[flt, dbl, fixflg, fixdbl] / ffpkne[edfg] + (fitsfile *fptr, char *keyroot, int nstart, int nkey, + DTYPE *numval, int decimals, char **comment, > int *status) +- +>4 Copy an indexed keyword from one HDU to another, modifying + the index number of the keyword name in the process. For example, + this routine could read the TLMIN3 keyword from the input HDU + (by giving keyroot = `TLMIN' and innum = 3) and write it to the + output HDU with the keyword name TLMIN4 (by setting outnum = 4). + If the input keyword does not exist, then this routine simply +> returns without indicating an error. \label{ffcpky} +- + int fits_copy_key / ffcpky + (fitsfile *infptr, fitsfile *outfptr, int innum, int outnum, + char *keyroot, > int *status) +- +>5 Write (append) a `triple precision' keyword into the CHU in F28.16 format. + The floating point keyword value is constructed by concatenating the + input integer value with the input double precision fraction value + (which must have a value between 0.0 and 1.0). The ffgkyt routine should + be used to read this keyword value, because the other keyword reading +> routines will not preserve the full precision of the value. \label{ffpkyt} +- + int fits_write_key_triple / ffpkyt + (fitsfile *fptr, char *keyname, long intval, double frac, + char *comment, > int *status) +- +>6 Write keywords to the CHDU that are defined in an ASCII template file. + The format of the template file is described under the fits\_parse\_template +> routine. \label{ffpktp} +- + int fits_write_key_template / ffpktp + (fitsfile *fptr, const char *filename, > int *status) +- +***4. Insert Keyword Routines + +These insert routines are somewhat less efficient than the `update' or +`write' keyword routines because the following keywords in the header +must be shifted down to make room for the inserted keyword. See +Appendix B for the definition of the parameters used in these +routines. + +>1 Insert a new keyword record into the CHU at the specified position + (i.e., immediately preceding the (keynum)th keyword in the header.) +> \label{ffirec} +- + int fits_insert_record / ffirec + (fitsfile *fptr, int keynum, char *card, > int *status) +- +>2 Insert a new keyword into the CHU. The new keyword is inserted + immediately following the last keyword that has been read from the + header. The `longstr' version has the same functionality as the + `str' version except that it also supports the local long string + keyword convention for strings longer than 68 characters. A null + pointer may be entered for the comment parameter which will cause + the comment field to be left blank. The flt, dbl, cmp, and dblcmp + versions of this routine have the added + feature that if the 'decimals' parameter is negative, then the 'G' + display format rather then the 'E' format will be used when + constructing the keyword value, taking the absolute value of + 'decimals' for the precision. This will suppress trailing zeros, + and will use a fixed format rather than an exponential format, +> depending on the magnitude of the value. \label{ffikyx} +- + int fits_insert_card / ffikey + (fitsfile *fptr, char *card, > int *status) + + int fits_insert_key_[str, longstr] / ffi[kys, kls] + (fitsfile *fptr, char *keyname, char *value, char *comment, + > int *status) + + int fits_insert_key_[log, lng] / ffiky[lj] + (fitsfile *fptr, char *keyname, DTYPE numval, char *comment, + > int *status) + + int fits_insert_key_[flt, fixflt, dbl, fixdbl] / ffiky[edfg] + (fitsfile *fptr, char *keyname, DTYPE numval, int decimals, + char *comment, > int *status) + + int fits_insert_key_[cmp, dblcmp, fixcmp, fixdblcmp] / ffik[yc,ym,fc,fm] + (fitsfile *fptr, char *keyname, DTYPE *numval, int decimals, + char *comment, > int *status) +- +>3 Insert a new keyword with an undefined, or null, value into the CHU. +> The value string of the keyword is left blank in this case. \label{ffikyu} +- + int fits_insert_key_null / ffikyu + (fitsfile *fptr, char *keyname, char *comment, > int *status) +- + +***5. Read Keyword Routines + +Wild card characters may be used when specifying the name of the +keyword to be read. + +>1 Read a keyword value (with the appropriate data type) and comment from + the CHU. If a NULL comment pointer is given on input, then the comment + string will not be returned. If the value of the keyword is not defined + (i.e., the value field is blank) then an error status = VALUE\_UNDEFINED + will be returned and the input value will not be changed (except that + ffgkys will reset the value to a null string). +> \label{ffgkyx} \label{ffgkls} +- + int fits_read_key_str / ffgkys + (fitsfile *fptr, char *keyname, > char *value, char *comment, + int *status); + + NOTE: after calling the following routine, programs must explicitly free + the memory allocated for 'longstr' after it is no longer needed or + call fits_free_memory. + + int fits_read_key_longstr / ffgkls + (fitsfile *fptr, char *keyname, > char **longstr, char *comment, + int *status) + + int fits_free_memory / fffree + (char *longstr, int *status); + + int fits_read_key_[log, lng, flt, dbl, cmp, dblcmp] / ffgky[ljedcm] + (fitsfile *fptr, char *keyname, > DTYPE *numval, char *comment, + int *status) + + int fits_read_key_lnglng / ffgkyjj + (fitsfile *fptr, char *keyname, > LONGLONG *numval, char *comment, + int *status) +- +>2 Read a sequence of indexed keyword values (e.g., NAXIS1, NAXIS2, ...). + The input starting index number (nstart) must be greater than 0. + If the value of any of the keywords is not defined (i.e., the value + field is blank) then an error status = VALUE\_UNDEFINED will be + returned and the input value for the undefined keyword(s) will not + be changed. These routines do not support wild card characters in + the root name. If there are no indexed keywords in the header with + the input root name then these routines do not return a non-zero +> status value and instead simply return nfound = 0. \label{ffgknx} +- + int fits_read_keys_str / ffgkns + (fitsfile *fptr, char *keyname, int nstart, int nkeys, + > char **value, int *nfound, int *status) + + int fits_read_keys_[log, lng, flt, dbl] / ffgkn[ljed] + (fitsfile *fptr, char *keyname, int nstart, int nkeys, + > DTYPE *numval, int *nfound, int *status) +- +>3 Read the value of a floating point keyword, returning the integer and + fractional parts of the value in separate routine arguments. + This routine may be used to read any keyword but is especially + useful for reading the 'triple precision' keywords written by ffpkyt. +> \label{ffgkyt} +- + int fits_read_key_triple / ffgkyt + (fitsfile *fptr, char *keyname, > long *intval, double *frac, + char *comment, int *status) +- +***6. Modify Keyword Routines + +These routines modify the value of an existing keyword. An error is +returned if the keyword does not exist. Wild card characters may be +used when specifying the name of the keyword to be modified. See +Appendix B for the definition of the parameters used in these +routines. + +>>1 Modify (overwrite) the nth 80-character header record in the CHU. \label{ffmrec} +- + int fits_modify_record / ffmrec + (fitsfile *fptr, int keynum, char *card, > int *status) +- +>2 Modify (overwrite) the 80-character header record for the named keyword + in the CHU. This can be used to overwrite the name of the keyword as +> well as its value and comment fields. \label{ffmcrd} +- + int fits_modify_card / ffmcrd + (fitsfile *fptr, char *keyname, char *card, > int *status) +- +>5 Modify the value and comment fields of an existing keyword in the CHU. + The `longstr' version has the same functionality as the `str' + version except that it also supports the local long string keyword + convention for strings longer than 68 characters. Optionally, one + may modify only the value field and leave the comment field + unchanged by setting the input COMMENT parameter equal to the + ampersand character (\&) or by entering a null pointer for the + comment parameter. The flt, dbl, cmp, and dblcmp versions of this + routine have the added feature that if the 'decimals' parameter is + negative, then the 'G' display format rather then the 'E' format + will be used when constructing the keyword value, taking the + absolute value of 'decimals' for the precision. This will suppress + trailing zeros, and will use a fixed format rather than an + exponential format, +> depending on the magnitude of the value. \label{ffmkyx} +- + int fits_modify_key_[str, longstr] / ffm[kys, kls] + (fitsfile *fptr, char *keyname, char *value, char *comment, + > int *status); + + int fits_modify_key_[log, lng] / ffmky[lj] + (fitsfile *fptr, char *keyname, DTYPE numval, char *comment, + > int *status) + + int fits_modify_key_[flt, dbl, fixflt, fixdbl] / ffmky[edfg] + (fitsfile *fptr, char *keyname, DTYPE numval, int decimals, + char *comment, > int *status) + + int fits_modify_key_[cmp, dblcmp, fixcmp, fixdblcmp] / ffmk[yc,ym,fc,fm] + (fitsfile *fptr, char *keyname, DTYPE *numval, int decimals, + char *comment, > int *status) +- +>6 Modify the value of an existing keyword to be undefined, or null. + The value string of the keyword is set to blank. + Optionally, one may leave the comment field unchanged by setting the + input COMMENT parameter equal to +> the ampersand character (\&) or by entering a null pointer. \label{ffmkyu} +- + int fits_modify_key_null / ffmkyu + (fitsfile *fptr, char *keyname, char *comment, > int *status) +- +***7. Update Keyword Routines + +>1 These update routines modify the value, and optionally the comment field, + of the keyword if it already exists, otherwise the new keyword is + appended to the header. A separate routine is provided for each + keyword data type. The `longstr' version has the same functionality + as the `str' version except that it also supports the local long + string keyword convention for strings longer than 68 characters. A + null pointer may be entered for the comment parameter which will + leave the comment field unchanged or blank. The flt, dbl, cmp, and + dblcmp versions of this routine have the added feature that if the + 'decimals' parameter is negative, then the 'G' display format + rather then the 'E' format will be used when constructing the + keyword value, taking the absolute value of 'decimals' for the + precision. This will suppress trailing zeros, and will use a fixed + format rather than an exponential format, +> depending on the magnitude of the value. \label{ffukyx} +- + int fits_update_key_[str, longstr] / ffu[kys, kls] + (fitsfile *fptr, char *keyname, char *value, char *comment, + > int *status) + + int fits_update_key_[log, lng] / ffuky[lj] + (fitsfile *fptr, char *keyname, DTYPE numval, char *comment, + > int *status) + + int fits_update_key_[flt, dbl, fixflt, fixdbl] / ffuky[edfg] + (fitsfile *fptr, char *keyname, DTYPE numval, int decimals, + char *comment, > int *status) + + int fits_update_key_[cmp, dblcmp, fixcmp, fixdblcmp] / ffuk[yc,ym,fc,fm] + (fitsfile *fptr, char *keyname, DTYPE *numval, int decimals, + char *comment, > int *status) +- + +**D. Define Data Scaling and Undefined Pixel Parameters + +These routines set or modify the internal parameters used by CFITSIO +to either scale the data or to represent undefined pixels. Generally +CFITSIO will scale the data according to the values of the BSCALE and +BZERO (or TSCALn and TZEROn) keywords, however these routines may be +used to override the keyword values. This may be useful when one wants +to read or write the raw unscaled values in the FITS file. Similarly, +CFITSIO generally uses the value of the BLANK or TNULLn keyword to +signify an undefined pixel, but these routines may be used to override +this value. These routines do not create or modify the corresponding +header keyword values. See Appendix B for the definition of the +parameters used in these routines. + +>1 Reset the scaling factors in the primary array or image extension; does + not change the BSCALE and BZERO keyword values and only affects the + automatic scaling performed when the data elements are written/read + to/from the FITS file. When reading from a FITS file the returned + data value = (the value given in the FITS array) * BSCALE + BZERO. + The inverse formula is used when writing data values to the FITS +> file. \label{ffpscl} +- + int fits_set_bscale / ffpscl + (fitsfile *fptr, double scale, double zero, > int *status) +- +>2 Reset the scaling parameters for a table column; does not change + the TSCALn or TZEROn keyword values and only affects the automatic + scaling performed when the data elements are written/read to/from + the FITS file. When reading from a FITS file the returned data + value = (the value given in the FITS array) * TSCAL + TZERO. The + inverse formula is used when writing data values to the FITS file. +> \label{fftscl} +- + int fits_set_tscale / fftscl + (fitsfile *fptr, int colnum, double scale, double zero, + > int *status) +- +>3 Define the integer value to be used to signify undefined pixels in the + primary array or image extension. This is only used if BITPIX = 8, 16, + or 32. This does not create or change the value of the BLANK keyword in +> the header. \label{ffpnul} +- + int fits_set_imgnull / ffpnul + (fitsfile *fptr, LONGLONG nulval, > int *status) +- +>4 Define the string to be used to signify undefined pixels in + a column in an ASCII table. This does not create or change the value +> of the TNULLn keyword. \label{ffsnul} +- + int fits_set_atblnull / ffsnul + (fitsfile *fptr, int colnum, char *nulstr, > int *status) +- +>5 Define the value to be used to signify undefined pixels in + an integer column in a binary table (where TFORMn = 'B', 'I', or 'J'). + This does not create or change the value of the TNULLn keyword. +> \label{fftnul} +- + int fits_set_btblnull / fftnul + (fitsfile *fptr, int colnum, LONGLONG nulval, > int *status) +- + +**E. Specialized FITS Primary Array or IMAGE Extension I/O Routines + +These routines read or write data values in the primary data array +(i.e., the first HDU in the FITS file) or an IMAGE extension. +Automatic data type conversion is performed for if the data type of the +FITS array (as defined by the BITPIX keyword) differs from the data +type of the array in the calling routine. The data values are +automatically scaled by the BSCALE and BZERO header values as they are +being written or read from the FITS array. Unlike the basic routines +described in the previous chapter, most of these routines specifically +support the FITS random groups format. See Appendix B for the +definition of the parameters used in these routines. + +The more primitive reading and writing routines (i. e., ffppr\_, +ffppn\_, ffppn, ffgpv\_, or ffgpf\_) simply treat the primary array as +a long 1-dimensional array of pixels, ignoring the intrinsic +dimensionality of the array. When dealing with a 2D image, for +example, the application program must calculate the pixel offset in the +1-D array that corresponds to any particular X, Y coordinate in the +image. C programmers should note that the ordering of arrays in FITS +files, and hence in all the CFITSIO calls, is more similar to the +dimensionality of arrays in Fortran rather than C. For instance if a +FITS image has NAXIS1 = 100 and NAXIS2 = 50, then a 2-D array just +large enough to hold the image should be declared as array[50][100] and +not as array[100][50]. + +For convenience, higher-level routines are also provided to specifically +deal with 2D images (ffp2d\_ and ffg2d\_) and 3D data cubes (ffp3d\_ +and ffg3d\_). The dimensionality of the FITS image is passed by the +naxis1, naxis2, and naxis3 parameters and the declared dimensions of +the program array are passed in the dim1 and dim2 parameters. Note +that the dimensions of the program array may be larger than the +dimensions of the FITS array. For example if a FITS image with NAXIS1 += NAXIS2 = 400 is read into a program array which is dimensioned as 512 +x 512 pixels, then the image will just fill the lower left corner of +the array with pixels in the range 1 - 400 in the X an Y directions. +This has the effect of taking a contiguous set of pixel value in the +FITS array and writing them to a non-contiguous array in program memory +(i.e., there are now some blank pixels around the edge of the image in +the program array). + +The most general set of routines (ffpss\_, ffgsv\_, and ffgsf\_) may be +used to transfer a rectangular subset of the pixels in a FITS +N-dimensional image to or from an array which has been declared in the +calling program. The fpixel and lpixel parameters are integer arrays +which specify the starting and ending pixel coordinate in each dimension +(starting with 1, not 0) of the FITS image that is to be read or +written. It is important to note that these are the starting and +ending pixels in the FITS image, not in the declared array in the +program. The array parameter in these routines is treated simply as a +large one-dimensional array of the appropriate data type containing the +pixel values; The pixel values in the FITS array are read/written +from/to this program array in strict sequence without any gaps; it is +up to the calling routine to correctly interpret the dimensionality of +this array. The two FITS reading routines (ffgsv\_ and ffgsf\_ ) also +have an `inc' parameter which defines the data sampling interval in +each dimension of the FITS array. For example, if inc[0]=2 and +inc[1]=3 when reading a 2-dimensional FITS image, then only every other +pixel in the first dimension and every 3rd pixel in the second +dimension will be returned to the 'array' parameter. + +Two types of routines are provided to read the data array which differ in +the way undefined pixels are handled. The first type of routines (e.g., +ffgpv\_) simply return an array of data elements in which undefined +pixels are set equal to a value specified by the user in the `nulval' +parameter. An additional feature of these routines is that if the user +sets nulval = 0, then no checks for undefined pixels will be performed, +thus reducing the amount of CPU processing. The second type of routines +(e.g., ffgpf\_) returns the data element array and, in addition, a char +array that indicates whether the value of the corresponding data pixel +is undefined (= 1) or defined (= 0). The latter type of routines may +be more convenient to use in some circumstances, however, it requires +an additional array of logical values which can be unwieldy when working +with large data arrays. + +>1 Write elements into the FITS data array. +> \label{ffppr} \label{ffpprx} \label{ffppn} \label{ffppnx} +- + int fits_write_img / ffppr + (fitsfile *fptr, int datatype, LONGLONG firstelem, LONGLONG nelements, + DTYPE *array, int *status); + + int fits_write_img_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffppr[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, LONGLONG firstelem, LONGLONG nelements, + DTYPE *array, > int *status); + + int fits_write_imgnull / ffppn + (fitsfile *fptr, int datatype, LONGLONG firstelem, LONGLONG nelements, + DTYPE *array, DTYPE *nulval, > int *status); + + int fits_write_imgnull_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffppn[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, LONGLONG firstelem, + LONGLONG nelements, DTYPE *array, DTYPE nulval, > int *status); +- +>>2 Set data array elements as undefined. \label{ffppru} +- + int fits_write_img_null / ffppru + (fitsfile *fptr, long group, LONGLONG firstelem, LONGLONG nelements, + > int *status) +- +>3 Write values into group parameters. This routine only applies + to the `Random Grouped' FITS format which has been used for + applications in radio interferometry, but is officially deprecated +> for future use. \label{ffpgpx} +- + int fits_write_grppar_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffpgp[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, long firstelem, long nelements, + > DTYPE *array, int *status) +- +>>4 Write a 2-D or 3-D image into the data array. \label{ffp2dx} \label{ffp3dx} +- + int fits_write_2d_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffp2d[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, LONGLONG dim1, LONGLONG naxis1, + LONGLONG naxis2, DTYPE *array, > int *status) + + int fits_write_3d_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffp3d[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, LONGLONG dim1, LONGLONG dim2, LONGLONG naxis1, + LONGLONG naxis2, LONGLONG naxis3, DTYPE *array, > int *status) +- +>>5 Write an arbitrary data subsection into the data array. \label{ffpssx} +- + int fits_write_subset_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffpss[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, long naxis, long *naxes, + long *fpixel, long *lpixel, DTYPE *array, > int *status) +- +>6 Read elements from the FITS data array. +> \label{ffgpv} \label{ffgpvx} \label{ffgpf} \label{ffgpfx} +- + int fits_read_img / ffgpv + (fitsfile *fptr, int datatype, long firstelem, long nelements, + DTYPE *nulval, > DTYPE *array, int *anynul, int *status) + + int fits_read_img_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffgpv[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, long firstelem, long nelements, + DTYPE nulval, > DTYPE *array, int *anynul, int *status) + + int fits_read_imgnull / ffgpf + (fitsfile *fptr, int datatype, long firstelem, long nelements, + > DTYPE *array, char *nullarray, int *anynul, int *status) + + int fits_read_imgnull_[byt, sht, usht, int, uint, lng, ulng, flt, dbl] / + ffgpf[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, long firstelem, long nelements, + > DTYPE *array, char *nullarray, int *anynul, int *status) +- +>7 Read values from group parameters. This routine only applies + to the `Random Grouped' FITS format which has been used for + applications in radio interferometry, but is officially deprecated +> for future use. \label{ffggpx} +- + int fits_read_grppar_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffggp[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, long firstelem, long nelements, + > DTYPE *array, int *status) +- +>8 Read 2-D or 3-D image from the data array. Undefined + pixels in the array will be set equal to the value of 'nulval', + unless nulval=0 in which case no testing for undefined pixels will +> be performed. \label{ffg2dx} \label{ffg3dx} +- + int fits_read_2d_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffg2d[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, DTYPE nulval, LONGLONG dim1, LONGLONG naxis1, + LONGLONG naxis2, > DTYPE *array, int *anynul, int *status) + + int fits_read_3d_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffg3d[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, long group, DTYPE nulval, LONGLONG dim1, + LONGLONG dim2, LONGLONG naxis1, LONGLONG naxis2, LONGLONG naxis3, + > DTYPE *array, int *anynul, int *status) +- +>9 Read an arbitrary data subsection from the data array. +> \label{ffgsvx} \label{ffgsfx} +- + int fits_read_subset_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffgsv[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, int group, int naxis, long *naxes, + long *fpixel, long *lpixel, long *inc, DTYPE nulval, + > DTYPE *array, int *anynul, int *status) + + int fits_read_subsetnull_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffgsf[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, int group, int naxis, long *naxes, + long *fpixel, long *lpixel, long *inc, > DTYPE *array, + char *nullarray, int *anynul, int *status) +- + +**F. Specialized FITS ASCII and Binary Table Routines + +***1. General Column Routines + +>1 Get information about an existing ASCII or binary table column. A null + pointer may be given for any of the output parameters that are not + needed. DATATYPE is a character string which returns the data type + of the column as defined by the TFORMn keyword (e.g., 'I', 'J','E', + 'D', etc.). In the case of an ASCII character column, typecode + will have a value of the form 'An' where 'n' is an integer + expressing the width of the field in characters. For example, if + TFORM = '160A8' then ffgbcl will return typechar='A8' and + repeat=20. All the returned parameters are scalar quantities. +> \label{ffgacl} \label{ffgbcl} +- + int fits_get_acolparms / ffgacl + (fitsfile *fptr, int colnum, > char *ttype, long *tbcol, + char *tunit, char *tform, double *scale, double *zero, + char *nulstr, char *tdisp, int *status) + + int fits_get_bcolparms / ffgbcl + (fitsfile *fptr, int colnum, > char *ttype, char *tunit, + char *typechar, long *repeat, double *scale, double *zero, + long *nulval, char *tdisp, int *status) + + int fits_get_bcolparmsll / ffgbclll + (fitsfile *fptr, int colnum, > char *ttype, char *tunit, + char *typechar, LONGLONG *repeat, double *scale, double *zero, + LONGLONG *nulval, char *tdisp, int *status) +- +>2 Return optimal number of rows to read or write at one time for + maximum I/O efficiency. Refer to the + ``Optimizing Code'' section in Chapter 5 for more discussion on how +> to use this routine. \label{ffgrsz} +- + int fits_get_rowsize / ffgrsz + (fitsfile *fptr, long *nrows, *status) +- +>3 Define the zero indexed byte offset of the 'heap' measured from + the start of the binary table data. By default the heap is assumed + to start immediately following the regular table data, i.e., at + location NAXIS1 x NAXIS2. This routine is only relevant for + binary tables which contain variable length array columns (with + TFORMn = 'Pt'). This routine also automatically writes + the value of theap to a keyword in the extension header. This + routine must be called after the required keywords have been + written (with ffphbn) +> but before any data is written to the table. \label{ffpthp} +- + int fits_write_theap / ffpthp + (fitsfile *fptr, long theap, > int *status) +- +>4 Test the contents of the binary table variable array heap, returning + the size of the heap, the number of unused bytes that are not currently + pointed to by any of the descriptors, and the number of bytes which are + pointed to by multiple descriptors. It also returns valid = FALSE if + any of the descriptors point to invalid addresses out of range of the +> heap. \label{fftheap} +- + int fits_test_heap / fftheap + (fitsfile *fptr, > LONGLONG *heapsize, LONGLONG *unused, LONGLONG *overlap, + int *validheap, int *status) +- +>5 Re-pack the vectors in the binary table variable array heap to recover + any unused space. Normally, when a vector in a variable length + array column is rewritten the previously written array remains in + the heap as wasted unused space. This routine will repack the + arrays that are still in use, thus eliminating any bytes in the + heap that are no longer in use. Note that if several vectors point + to the same bytes in the heap, then this routine will make + duplicate copies of the bytes for each vector, which will actually +> expand the size of the heap. \label{ffcmph} +- + int fits_compress_heap / ffcmph + (fitsfile *fptr, > int *status) +- + +***2. Low-Level Table Access Routines + +The following 2 routines provide low-level access to the data in ASCII +or binary tables and are mainly useful as an efficient way to copy all +or part of a table from one location to another. These routines simply +read or write the specified number of consecutive bytes in an ASCII or +binary table, without regard for column boundaries or the row length in +the table. These routines do not perform any machine dependent data +conversion or byte swapping. See Appendix B for the definition of the +parameters used in these routines. + +>1 Read or write a consecutive array of bytes from an ASCII or binary +> table \label{ffgtbb} \label{ffptbb} +- + int fits_read_tblbytes / ffgtbb + (fitsfile *fptr, LONGLONG firstrow, LONGLONG firstchar, LONGLONG nchars, + > unsigned char *values, int *status) + + int fits_write_tblbytes / ffptbb + (fitsfile *fptr, LONGLONG firstrow, LONGLONG firstchar, LONGLONG nchars, + unsigned char *values, > int *status) +- + +***3. Write Column Data Routines + +>1 Write elements into an ASCII or binary table column (in the CDU). + The data type of the array is implied by the suffix of the +> routine name. \label{ffpcls} +- + int fits_write_col_str / ffpcls + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG firstelem, + LONGLONG nelements, char **array, > int *status) + + int fits_write_col_[log,byt,sht,usht,int,uint,lng,ulng,lnglng,flt,dbl,cmp,dblcmp] / + ffpcl[l,b,i,ui,k,uk,j,uj,jj,e,d,c,m] + (fitsfile *fptr, int colnum, LONGLONG firstrow, + LONGLONG firstelem, LONGLONG nelements, DTYPE *array, > int *status) +- +>2 Write elements into an ASCII or binary table column + substituting the appropriate FITS null value for any elements that +> are equal to the nulval parameter. \label{ffpcnx} +- + int fits_write_colnull_[log, byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffpcn[l,b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG firstelem, + LONGLONG nelements, DTYPE *array, DTYPE nulval, > int *status) +- +>3 Write string elements into a binary table column (in the CDU) + substituting the FITS null value for any elements that +> are equal to the nulstr string. \label{ffpcns} +- + int fits_write_colnull_str / ffpcns + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG firstelem, + LONGLONG nelements, char **array, char *nulstr, > int *status) +- +>4 Write bit values into a binary byte ('B') or bit ('X') table column (in + the CDU). Larray is an array of characters corresponding to the + sequence of bits to be written. If an element of larray is true + (not equal to zero) then the corresponding bit in the FITS table is + set to 1, otherwise the bit is set to 0. The 'X' column in a FITS + table is always padded out to a multiple of 8 bits where the bit + array starts with the most significant bit of the byte and works + down towards the 1's bit. For example, a '4X' array, with the + first bit = 1 and the remaining 3 bits = 0 is equivalent to the 8-bit + unsigned byte decimal value of 128 ('1000 0000B'). In the case of + 'X' columns, CFITSIO can write to all 8 bits of each byte whether + they are formally valid or not. Thus if the column is defined as + '4X', and one calls ffpclx with firstbit=1 and nbits=8, then all + 8 bits will be written into the first byte (as opposed to writing + the first 4 bits into the first row and then the next 4 bits into + the next row), even though the last 4 bits of each byte are formally + not defined and should all be set = 0. It should also be noted that + it is more efficient to write 'X' columns an entire byte at a time, + instead of bit by bit. Any of the CFITSIO routines that write to + columns (e.g. fits\_write\_col\_byt) may be used for this purpose. + These routines will interpret 'X' columns as though they were 'B' + columns (e.g., '1X' through '8X' is equivalent +> to '1B', and '9X' through '16X' is equivalent to '2B'). \label{ffpclx} +- + int fits_write_col_bit / ffpclx + (fitsfile *fptr, int colnum, LONGLONG firstrow, long firstbit, + long nbits, char *larray, > int *status) +- +>5 Write the descriptor for a variable length column in a binary table. + This routine can be used in conjunction with ffgdes to enable + 2 or more arrays to point to the same storage location to save +> storage space if the arrays are identical. \label{ffpdes} +- + int fits_write_descript / ffpdes + (fitsfile *fptr, int colnum, LONGLONG rownum, LONGLONG repeat, + LONGLONG offset, > int *status) +- +***4. Read Column Data Routines + +Two types of routines are provided to get the column data which differ +in the way undefined pixels are handled. The first set of routines +(ffgcv) simply return an array of data elements in which undefined +pixels are set equal to a value specified by the user in the 'nullval' +parameter. If nullval = 0, then no checks for undefined pixels will be +performed, thus increasing the speed of the program. The second set of +routines (ffgcf) returns the data element array and in addition a +logical array of flags which defines whether the corresponding data +pixel is undefined. See Appendix B for the definition of the +parameters used in these routines. + + Any column, regardless of it's intrinsic data type, may be read as a + string. It should be noted however that reading a numeric column as + a string is 10 - 100 times slower than reading the same column as a number + due to the large overhead in constructing the formatted strings. + The display format of the returned strings will be + determined by the TDISPn keyword, if it exists, otherwise by the + data type of the column. The length of the returned strings (not + including the null terminating character) can be determined with + the fits\_get\_col\_display\_width routine. The following TDISPn + display formats are currently supported: +- + Iw.m Integer + Ow.m Octal integer + Zw.m Hexadecimal integer + Fw.d Fixed floating point + Ew.d Exponential floating point + Dw.d Exponential floating point + Gw.d General; uses Fw.d if significance not lost, else Ew.d +- + where w is the width in characters of the displayed values, m is + the minimum number of digits displayed, and d is the number of + digits to the right of the decimal. The .m field is optional. + +>1 Read elements from an ASCII or binary table column (in the CDU). These + routines return the values of the table column array elements. Undefined + array elements will be returned with a value = nulval, unless nulval = 0 + (or = ' ' for ffgcvs) in which case no checking for undefined values will + be performed. The ANYF parameter is set to true if any of the returned +> elements are undefined. \label{ffgcvx} +- + int fits_read_col_str / ffgcvs + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG firstelem, + LONGLONG nelements, char *nulstr, > char **array, int *anynul, + int *status) + + int fits_read_col_[log,byt,sht,usht,int,uint,lng,ulng, lnglng, flt, dbl, cmp, dblcmp] / + ffgcv[l,b,i,ui,k,uk,j,uj,jj,e,d,c,m] + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG firstelem, + LONGLONG nelements, DTYPE nulval, > DTYPE *array, int *anynul, + int *status) +- +>2 Read elements and null flags from an ASCII or binary table column (in the + CHDU). These routines return the values of the table column array elements. + Any undefined array elements will have the corresponding nullarray element + set equal to TRUE. The anynul parameter is set to true if any of the +> returned elements are undefined. \label{ffgcfx} +- + int fits_read_colnull_str / ffgcfs + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG firstelem, + LONGLONG nelements, > char **array, char *nullarray, int *anynul, + int *status) + + int fits_read_colnull_[log,byt,sht,usht,int,uint,lng,ulng,lnglng,flt,dbl,cmp,dblcmp] / + ffgcf[l,b,i,ui,k,uk,j,uj,jj,e,d,c,m] + (fitsfile *fptr, int colnum, LONGLONG firstrow, + LONGLONG firstelem, LONGLONG nelements, > DTYPE *array, + char *nullarray, int *anynul, int *status) +- +>3 Read an arbitrary data subsection from an N-dimensional array + in a binary table vector column. Undefined pixels + in the array will be set equal to the value of 'nulval', + unless nulval=0 in which case no testing for undefined pixels will + be performed. The first and last rows in the table to be read + are specified by fpixel(naxis+1) and lpixel(naxis+1), and hence + are treated as the next higher dimension of the FITS N-dimensional + array. The INC parameter specifies the sampling interval in +> each dimension between the data elements that will be returned. \label{ffgsvx2} +- + int fits_read_subset_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffgsv[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, int colnum, int naxis, long *naxes, long *fpixel, + long *lpixel, long *inc, DTYPE nulval, > DTYPE *array, int *anynul, + int *status) +- +>4 Read an arbitrary data subsection from an N-dimensional array + in a binary table vector column. Any Undefined + pixels in the array will have the corresponding 'nullarray' + element set equal to TRUE. The first and last rows in the table + to be read are specified by fpixel(naxis+1) and lpixel(naxis+1), + and hence are treated as the next higher dimension of the FITS + N-dimensional array. The INC parameter specifies the sampling + interval in each dimension between the data elements that will be +> returned. \label{ffgsfx2} +- + int fits_read_subsetnull_[byt, sht, usht, int, uint, lng, ulng, lnglng, flt, dbl] / + ffgsf[b,i,ui,k,uk,j,uj,jj,e,d] + (fitsfile *fptr, int colnum, int naxis, long *naxes, + long *fpixel, long *lpixel, long *inc, > DTYPE *array, + char *nullarray, int *anynul, int *status) +- +>5 Read bit values from a byte ('B') or bit (`X`) table column (in the + CDU). Larray is an array of logical values corresponding to the + sequence of bits to be read. If larray is true then the + corresponding bit was set to 1, otherwise the bit was set to 0. + The 'X' column in a FITS table is always padded out to a multiple + of 8 bits where the bit array starts with the most significant bit + of the byte and works down towards the 1's bit. For example, a + '4X' array, with the first bit = 1 and the remaining 3 bits = 0 is + equivalent to the 8-bit unsigned byte value of 128. + Note that in the case of 'X' columns, CFITSIO can read all 8 bits + of each byte whether they are formally valid or not. Thus if the + column is defined as '4X', and one calls ffgcx with firstbit=1 and + nbits=8, then all 8 bits will be read from the first byte (as + opposed to reading the first 4 bits from the first row and then the + first 4 bits from the next row), even though the last 4 bits of + each byte are formally not defined. It should also be noted that + it is more efficient to read 'X' columns an entire byte at a time, + instead of bit by bit. Any of the CFITSIO routines that read + columns (e.g. fits\_read\_col\_byt) may be used for this + purpose. These routines will interpret 'X' columns as though they + were 'B' columns (e.g., '8X' is equivalent to '1B', and '16X' is +> equivalent to '2B'). \label{ffgcx} +- + int fits_read_col_bit / ffgcx + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG firstbit, + LONGLONG nbits, > char *larray, int *status) +- +>6 Read any consecutive set of bits from an 'X' or 'B' column and + interpret them as an unsigned n-bit integer. nbits must be less + than 16 or 32 in ffgcxui and ffgcxuk, respectively. If nrows + is greater than 1, then the same set of bits will be read from + each row, starting with firstrow. The bits are numbered with + 1 = the most significant bit of the first element of the column. +> \label{ffgcxui} +- + int fits_read_col_bit_[usht, uint] / ffgcx[ui,uk] + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG, nrows, + long firstbit, long nbits, > DTYPE *array, int *status) +- +>7 Return the descriptor for a variable length column in a binary table. + The descriptor consists of 2 integer parameters: the number of elements + in the array and the starting offset relative to the start of the heap. + The first pair of routine returns a single descriptor whereas the second + pair of routine + returns the descriptors for a range of rows in the table. The only + difference between the 2 routines in each pair is that one returns + the parameters as 'long' integers, whereas the other returns the values + as 64-bit 'LONGLONG' integers. +> \label{ffgdes} +- + int fits_read_descript / ffgdes + (fitsfile *fptr, int colnum, LONGLONG rownum, > long *repeat, + long *offset, int *status) + + int fits_read_descriptll / ffgdesll + (fitsfile *fptr, int colnum, LONGLONG rownum, > LONGLONG *repeat, + LONGLONG *offset, int *status) + + int fits_read_descripts / ffgdess + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG nrows + > long *repeat, long *offset, int *status) + + int fits_read_descriptsll / ffgdessll + (fitsfile *fptr, int colnum, LONGLONG firstrow, LONGLONG nrows + > LONGLONG *repeat, LONGLONG *offset, int *status) +- + +*X. Extended File Name Syntax + +**A. Overview + +CFITSIO supports an extended syntax when specifying the name of the +data file to be opened or created that includes the following +features: + +\begin{itemize} +\item +CFITSIO can read IRAF format images which have header file names that +end with the '.imh' extension, as well as reading and writing FITS +files, This feature is implemented in CFITSIO by first converting the +IRAF image into a temporary FITS format file in memory, then opening +the FITS file. Any of the usual CFITSIO routines then may be used to +read the image header or data. Similarly, raw binary data arrays can +be read by converting them on the fly into virtual FITS images. + +\item +FITS files on the Internet can be read (and sometimes written) using the FTP, +HTTP, or ROOT protocols. + +\item +FITS files can be piped between tasks on the stdin and stdout streams. + +\item +FITS files can be read and written in shared memory. This can +potentially achieve better data I/O performance compared to reading and +writing the same FITS files on magnetic disk. + +\item +Compressed FITS files in gzip or Unix COMPRESS format can be directly read. + +\item +Output FITS files can be written directly in compressed gzip format, +thus saving disk space. + +\item +FITS table columns can be created, modified, or deleted 'on-the-fly' as +the table is opened by CFITSIO. This creates a virtual FITS file containing +the modifications that is then opened by the application program. + +\item +Table rows may be selected, or filtered out, on the fly when the table +is opened by CFITSIO, based on an user-specified expression. +Only rows for which the expression evaluates to 'TRUE' are retained +in the copy of the table that is opened by the application program. + +\item +Histogram images may be created on the fly by binning the values in +table columns, resulting in a virtual N-dimensional FITS image. The +application program then only sees the FITS image (in the primary +array) instead of the original FITS table. +\end{itemize} + +The latter 3 table filtering features in particular add very powerful +data processing capabilities directly into CFITSIO, and hence into +every task that uses CFITSIO to read or write FITS files. For example, +these features transform a very simple program that just copies an +input FITS file to a new output file (like the `fitscopy' program that +is distributed with CFITSIO) into a multipurpose FITS file processing +tool. By appending fairly simple qualifiers onto the name of the input +FITS file, the user can perform quite complex table editing operations +(e.g., create new columns, or filter out rows in a table) or create +FITS images by binning or histogramming the values in table columns. +In addition, these functions have been coded using new state-of-the art +algorithms that are, in some cases, 10 - 100 times faster than previous +widely used implementations. + +Before describing the complete syntax for the extended FITS file names +in the next section, here are a few examples of FITS file names that +give a quick overview of the allowed syntax: + +\begin{itemize} +\item +{\tt myfile.fits}: the simplest case of a FITS file on disk in the current +directory. + +\item +{\tt myfile.imh}: opens an IRAF format image file and converts it on the +fly into a temporary FITS format image in memory which can then be read with +any other CFITSIO routine. + +\item +{\tt rawfile.dat[i512,512]}: opens a raw binary data array (a 512 x 512 +short integer array in this case) and converts it on the fly into a +temporary FITS format image in memory which can then be read with any +other CFITSIO routine. + +\item +{\tt myfile.fits.gz}: if this is the name of a new output file, the '.gz' +suffix will cause it to be compressed in gzip format when it is written to +disk. + +\item +{\tt myfile.fits.gz[events, 2]}: opens and uncompresses the gzipped file +myfile.fits then moves to the extension with the keywords EXTNAME += 'EVENTS' and EXTVER = 2. + +\item +{\tt -}: a dash (minus sign) signifies that the input file is to be read +from the stdin file stream, or that the output file is to be written to +the stdout stream. See also the stream:// driver which provides a +more efficient, but more restricted method of reading or writing to +the stdin or stdout streams. + +\item +{\tt ftp://legacy.gsfc.nasa.gov/test/vela.fits}: FITS files in any ftp +archive site on the Internet may be directly opened with read-only +access. + +\item +{\tt http://legacy.gsfc.nasa.gov/software/test.fits}: any valid URL to a +FITS file on the Web may be opened with read-only access. + +\item +{\tt root://legacy.gsfc.nasa.gov/test/vela.fits}: similar to ftp access +except that it provides write as well as read access to the files +across the network. This uses the root protocol developed at CERN. + +\item +{\tt shmem://h2[events]}: opens the FITS file in a shared memory segment and +moves to the EVENTS extension. + +\item +{\tt mem://}: creates a scratch output file in core computer memory. The +resulting 'file' will disappear when the program exits, so this +is mainly useful for testing purposes when one does not want a +permanent copy of the output file. + +\item +{\tt myfile.fits[3; Images(10)]}: opens a copy of the image contained in the +10th row of the 'Images' column in the binary table in the 3th extension +of the FITS file. The virtual file that is opened by the application just +contains this single image in the primary array. + +\item +{\tt myfile.fits[1:512:2, 1:512:2]}: opens a section of the input image +ranging from the 1st to the 512th pixel in X and Y, and selects every +second pixel in both dimensions, resulting in a 256 x 256 pixel input image +in this case. + +\item +{\tt myfile.fits[EVENTS][col Rad = sqrt(X**2 + Y**2)]}: creates and opens +a virtual file on the fly that is identical to +myfile.fits except that it will contain a new column in the EVENTS +extension called 'Rad' whose value is computed using the indicated +expression which is a function of the values in the X and Y columns. + +\item +{\tt myfile.fits[EVENTS][PHA > 5]}: creates and opens a virtual FITS +files that is identical to 'myfile.fits' except that the EVENTS table +will only contain the rows that have values of the PHA column greater +than 5. In general, any arbitrary boolean expression using a C or +Fortran-like syntax, which may combine AND and OR operators, +may be used to select rows from a table. + +\item +{\tt myfile.fits[EVENTS][bin (X,Y)=1,2048,4]}: creates a temporary FITS +primary array image which is computed on the fly by binning (i.e, +computing the 2-dimensional histogram) of the values in the X and Y +columns of the EVENTS extension. In this case the X and Y coordinates +range from 1 to 2048 and the image pixel size is 4 units in both +dimensions, so the resulting image is 512 x 512 pixels in size. + +\item +The final example combines many of these feature into one complex +expression (it is broken into several lines for clarity): +- + ftp://legacy.gsfc.nasa.gov/data/sample.fits.gz[EVENTS] + [col phacorr = pha * 1.1 - 0.3][phacorr >= 5.0 && phacorr <= 14.0] + [bin (X,Y)=32] +- +In this case, CFITSIO (1) copies and uncompresses the FITS file from +the ftp site on the legacy machine, (2) moves to the 'EVENTS' +extension, (3) calculates a new column called 'phacorr', (4) selects +the rows in the table that have phacorr in the range 5 to 14, and +finally (5) bins the remaining rows on the X and Y column coordinates, +using a pixel size = 32 to create a 2D image. All this processing is +completely transparent to the application program, which simply sees +the final 2-D image in the primary array of the opened file. +\end{itemize} + +The full extended CFITSIO FITS file name can contain several different +components depending on the context. These components are described in +the following sections: +- +When creating a new file: + filetype://BaseFilename(templateName)[compress] + +When opening an existing primary array or image HDU: + filetype://BaseFilename(outName)[HDUlocation][ImageSection][pixFilter] + +When opening an existing table HDU: + filetype://BaseFilename(outName)[HDUlocation][colFilter][rowFilter][binSpec] +- +The filetype, BaseFilename, outName, HDUlocation, ImageSection, and pixFilter +components, if present, must be given in that order, but the colFilter, +rowFilter, and binSpec specifiers may follow in any order. Regardless +of the order, however, the colFilter specifier, if present, will be +processed first by CFITSIO, followed by the rowFilter specifier, and +finally by the binSpec specifier. + +**A. Filetype + +The type of file determines the medium on which the file is located +(e.g., disk or network) and, hence, which internal device driver is used by +CFITSIO to read and/or write the file. Currently supported types are +- + file:// - file on local magnetic disk (default) + ftp:// - a readonly file accessed with the anonymous FTP protocol. + It also supports ftp://username:password@hostname/... + for accessing password-protected ftp sites. + http:// - a readonly file accessed with the HTTP protocol. It + supports username:password just like the ftp driver. + Proxy HTTP servers are supported using the http_proxy + environment variable (see following note). + stream:// - special driver to read an input FITS file from the stdin + stream, and/or write an output FITS file to the stdout + stream. This driver is fragile and has limited + functionality (see the following note). + gsiftp:// - access files on a computational grid using the gridftp + protocol in the Globus toolkit (see following note). + root:// - uses the CERN root protocol for writing as well as + reading files over the network (see following note). + shmem:// - opens or creates a file which persists in the computer's + shared memory (see following note). + mem:// - opens a temporary file in core memory. The file + disappears when the program exits so this is mainly + useful for test purposes when a permanent output file + is not desired. +- +If the filetype is not specified, then type file:// is assumed. +The double slashes '//' are optional and may be omitted in most cases. + +***1. Notes about HTTP proxy servers + +A proxy HTTP server may be used by defining the address (URL) and port +number of the proxy server with the http\_proxy environment variable. +For example +- + setenv http_proxy http://heasarc.gsfc.nasa.gov:3128 +- +will cause CFITSIO to use port 3128 on the heasarc proxy server whenever +reading a FITS file with HTTP. + +***2. Notes about the stream filetype driver + +The stream driver can be used to efficiently read a FITS file from the stdin +file stream or write a FITS to the stdout file stream. However, because these +input and output streams must be accessed sequentially, the FITS file reading or +writing application must also read and write the file sequentially, at least +within the tolerances described below. + +CFITSIO supports 2 different methods for accessing FITS files on the stdin and +stdout streams. The original method, which is invoked by specifying a dash +character, "-", as the name of the file when opening or creating it, works by +storing a complete copy of the entire FITS file in memory. In this case, when +reading from stdin, CFITSIO will copy the entire stream into memory before doing +any processing of the file. Similarly, when writing to stdout, CFITSIO will +create a copy of the entire FITS file in memory, before finally flushing it out +to the stdout stream when the FITS file is closed. Buffering the entire FITS +file in this way allows the application to randomly access any part of the FITS +file, in any order, but it also requires that the user have sufficient available +memory (or virtual memory) to store the entire file, which may not be possible +in the case of very large files. + +The newer stream filetype provides a more memory-efficient method of accessing +FITS files on the stdin or stdout streams. Instead of storing a copy of the +entire FITS file in memory, CFITSIO only uses a set of internal buffer which by +default can store 40 FITS blocks, or about 100K bytes of the FITS file. The +application program must process the FITS file sequentially from beginning to +end, within this 100K buffer. Generally speaking the application program must +conform to the following restrictions: + +\begin{itemize} +\item +The program must finish reading or writing the header keywords +before reading or writing any data in the HDU. +\item +The HDU can contain at most about 1400 header keywords. This is the +maximum that can fit in the nominal 40 FITS block buffer. In principle, +this limit could be increased by recompiling CFITSIO with a larger +buffer limit, which is set by the NIOBUF parameter in fitsio2.h. +\item +The program must read or write the data in a sequential manner from the +beginning to the end of the HDU. Note that CFITSIO's internal +100K buffer allows a little latitude in meeting this requirement. +\item +The program cannot move back to a previous HDU in the FITS file. +\item +Reading or writing of variable length array columns in binary tables is not +supported on streams, because this requires moving back and forth between the +fixed-length portion of the binary table and the following heap area where the +arrays are actually stored. +\item +Reading or writing of tile-compressed images is not supported on streams, +because the images are internally stored using variable length arrays. +\end{itemize} + +***3. Notes about the gsiftp filetype + +DEPENDENCIES: Globus toolkit (2.4.3 or higher) (GT) should be installed. +There are two different ways to install GT: + +1) goto the globus toolkit web page www.globus.org and follow the + download and compilation instructions; + +2) goto the Virtual Data Toolkit web page http://vdt.cs.wisc.edu/ + and follow the instructions (STRONGLY SUGGESTED); + +Once a globus client has been installed in your system with a specific flavour +it is possible to compile and install the CFITSIO libraries. +Specific configuration flags must be used: + +1) --with-gsiftp[[=PATH]] Enable Globus Toolkit gsiftp protocol support + PATH=GLOBUS\_LOCATION i.e. the location of your globus installation + +2) --with-gsiftp-flavour[[=PATH] defines the specific Globus flavour + ex. gcc32 + +Both the flags must be used and it is mandatory to set both the PATH and the +flavour. + +USAGE: To access files on a gridftp server it is necessary to use a gsiftp prefix: + +example: gsiftp://remote\_server\_fqhn/directory/filename + +The gridftp driver uses a local buffer on a temporary file the file is located +in the /tmp directory. If you have special permissions on /tmp or you do not have a /tmp +directory, it is possible to force another location setting the GSIFTP\_TMPFILE environment +variable (ex. export GSIFTP\_TMPFILE=/your/location/yourtmpfile). + +Grid FTP supports multi channel transfer. By default a single channel transmission is +available. However, it is possible to modify this behavior setting the GSIFTP\_STREAMS +environment variable (ex. export GSIFTP\_STREAMS=8). + + +***4. Notes about the root filetype + +The original rootd server can be obtained from: +\verb-ftp://root.cern.ch/root/rootd.tar.gz- +but, for it to work correctly with CFITSIO one has to use a modified +version which supports a command to return the length of the file. +This modified version is available in rootd subdirectory +in the CFITSIO ftp area at +- + ftp://legacy.gsfc.nasa.gov/software/fitsio/c/root/rootd.tar.gz. +- + +This small server is started either by inetd when a client requests a +connection to a rootd server or by hand (i.e. from the command line). +The rootd server works with the ROOT TNetFile class. It allows remote +access to ROOT database files in either read or write mode. By default +TNetFile assumes port 432 (which requires rootd to be started as root). +To run rootd via inetd add the following line to /etc/services: +- + rootd 432/tcp +- +and to /etc/inetd.conf, add the following line: +- + rootd stream tcp nowait root /user/rdm/root/bin/rootd rootd -i +- +Force inetd to reread its conf file with \verb+kill -HUP <pid inetd>+. +You can also start rootd by hand running directly under your private +account (no root system privileges needed). For example to start +rootd listening on port 5151 just type: \verb+rootd -p 5151+ +Notice that no \& is needed. Rootd will go into background by itself. +- + Rootd arguments: + -i says we were started by inetd + -p port# specifies a different port to listen on + -d level level of debug info written to syslog + 0 = no debug (default) + 1 = minimum + 2 = medium + 3 = maximum +- +Rootd can also be configured for anonymous usage (like anonymous ftp). +To setup rootd to accept anonymous logins do the following (while being +logged in as root): +- + - Add the following line to /etc/passwd: + + rootd:*:71:72:Anonymous rootd:/var/spool/rootd:/bin/false + + where you may modify the uid, gid (71, 72) and the home directory + to suite your system. + + - Add the following line to /etc/group: + + rootd:*:72:rootd + + where the gid must match the gid in /etc/passwd. + + - Create the directories: + + mkdir /var/spool/rootd + mkdir /var/spool/rootd/tmp + chmod 777 /var/spool/rootd/tmp + + Where /var/spool/rootd must match the rootd home directory as + specified in the rootd /etc/passwd entry. + + - To make writeable directories for anonymous do, for example: + + mkdir /var/spool/rootd/pub + chown rootd:rootd /var/spool/rootd/pub +- +That's all. Several additional remarks: you can login to an anonymous +server either with the names "anonymous" or "rootd". The password should +be of type user@host.do.main. Only the @ is enforced for the time +being. In anonymous mode the top of the file tree is set to the rootd +home directory, therefore only files below the home directory can be +accessed. Anonymous mode only works when the server is started via +inetd. + +***5. Notes about the shmem filetype: + +Shared memory files are currently supported on most Unix platforms, +where the shared memory segments are managed by the operating system +kernel and `live' independently of processes. They are not deleted (by +default) when the process which created them terminates, although they +will disappear if the system is rebooted. Applications can create +shared memory files in CFITSIO by calling: +- + fit_create_file(&fitsfileptr, "shmem://h2", &status); +- +where the root `file' names are currently restricted to be 'h0', 'h1', +'h2', 'h3', etc., up to a maximum number defined by the the value of +SHARED\_MAXSEG (equal to 16 by default). This is a prototype +implementation of the shared memory interface and a more robust +interface, which will have fewer restrictions on the number of files +and on their names, may be developed in the future. + +When opening an already existing FITS file in shared memory one calls +the usual CFITSIO routine: +- + fits_open_file(&fitsfileptr, "shmem://h7", mode, &status) +- +The file mode can be READWRITE or READONLY just as with disk files. +More than one process can operate on READONLY mode files at the same +time. CFITSIO supports proper file locking (both in READONLY and +READWRITE modes), so calls to fits\_open\_file may be locked out until +another other process closes the file. + +When an application is finished accessing a FITS file in a shared +memory segment, it may close it (and the file will remain in the +system) with fits\_close\_file, or delete it with fits\_delete\_file. +Physical deletion is postponed until the last process calls +ffclos/ffdelt. fits\_delete\_file tries to obtain a READWRITE lock on +the file to be deleted, thus it can be blocked if the object was not +opened in READWRITE mode. + +A shared memory management utility program called `smem', is included +with the CFITSIO distribution. It can be built by typing `make smem'; +then type `smem -h' to get a list of valid options. Executing smem +without any options causes it to list all the shared memory segments +currently residing in the system and managed by the shared memory +driver. To get a list of all the shared memory objects, run the system +utility program `ipcs [-a]'. + +**B. Base Filename + +The base filename is the name of the file optionally including the +director/subdirectory path, and in the case of `ftp', `http', and `root' +filetypes, the machine identifier. Examples: +- + myfile.fits + !data.fits + /data/myfile.fits + fits.gsfc.nasa.gov/ftp/sampledata/myfile.fits.gz +- + +When creating a new output file on magnetic disk (of type file://) if +the base filename begins with an exclamation point (!) then any +existing file with that same basename will be deleted prior to creating +the new FITS file. Otherwise if the file to be created already exists, +then CFITSIO will return an error and will not overwrite the existing +file. Note that the exclamation point, '!', is a special UNIX +character, so if it is used on the command line rather than entered at +a task prompt, it must be preceded by a backslash to force the UNIX +shell to pass it verbatim to the application program. + +If the output disk file name ends with the suffix '.gz', then CFITSIO +will compress the file using the gzip compression algorithm before +writing it to disk. This can reduce the amount of disk space used by +the file. Note that this feature requires that the uncompressed file +be constructed in memory before it is compressed and written to disk, +so it can fail if there is insufficient available memory. + +An input FITS file may be compressed with the gzip or Unix compress +algorithms, in which case CFITSIO will uncompress the file on the fly +into a temporary file (in memory or on disk). Compressed files may +only be opened with read-only permission. When specifying the name of +a compressed FITS file it is not necessary to append the file suffix +(e.g., `.gz' or `.Z'). If CFITSIO cannot find the input file name +without the suffix, then it will automatically search for a compressed +file with the same root name. In the case of reading ftp and http type +files, CFITSIO generally looks for a compressed version of the file +first, before trying to open the uncompressed file. By default, +CFITSIO copies (and uncompressed if necessary) the ftp or http FITS +file into memory on the local machine before opening it. This will +fail if the local machine does not have enough memory to hold the whole +FITS file, so in this case, the output filename specifier (see the next +section) can be used to further control how CFITSIO reads ftp and http +files. + +If the input file is an IRAF image file (*.imh file) then CFITSIO will +automatically convert it on the fly into a virtual FITS image before it +is opened by the application program. IRAF images can only be opened +with READONLY file access. + +Similarly, if the input file is a raw binary data array, then CFITSIO +will convert it on the fly into a virtual FITS image with the basic set +of required header keywords before it is opened by the application +program (with READONLY access). In this case the data type and +dimensions of the image must be specified in square brackets following +the filename (e.g. rawfile.dat[ib512,512]). The first character (case +insensitive) defines the data type of the array: +- + b 8-bit unsigned byte + i 16-bit signed integer + u 16-bit unsigned integer + j 32-bit signed integer + r or f 32-bit floating point + d 64-bit floating point +- +An optional second character specifies the byte order of the array +values: b or B indicates big endian (as in FITS files and the native +format of SUN UNIX workstations and Mac PCs) and l or L indicates +little endian (native format of DEC OSF workstations and IBM PCs). If +this character is omitted then the array is assumed to have the native +byte order of the local machine. These data type characters are then +followed by a series of one or more integer values separated by commas +which define the size of each dimension of the raw array. Arrays with +up to 5 dimensions are currently supported. Finally, a byte offset to +the position of the first pixel in the data file may be specified by +separating it with a ':' from the last dimension value. If omitted, it +is assumed that the offset = 0. This parameter may be used to skip +over any header information in the file that precedes the binary data. +Further examples: +- + raw.dat[b10000] 1-dimensional 10000 pixel byte array + raw.dat[rb400,400,12] 3-dimensional floating point big-endian array + img.fits[ib512,512:2880] reads the 512 x 512 short integer array in + a FITS file, skipping over the 2880 byte header +- + +One special case of input file is where the filename = `-' (a dash or +minus sign) or 'stdin' or 'stdout', which signifies that the input file +is to be read from the stdin stream, or written to the stdout stream if +a new output file is being created. In the case of reading from stdin, +CFITSIO first copies the whole stream into a temporary FITS file (in +memory or on disk), and subsequent reading of the FITS file occurs in +this copy. When writing to stdout, CFITSIO first constructs the whole +file in memory (since random access is required), then flushes it out +to the stdout stream when the file is closed. In addition, if the +output filename = '-.gz' or 'stdout.gz' then it will be gzip compressed +before being written to stdout. + +This ability to read and write on the stdin and stdout steams allows +FITS files to be piped between tasks in memory rather than having to +create temporary intermediate FITS files on disk. For example if task1 +creates an output FITS file, and task2 reads an input FITS file, the +FITS file may be piped between the 2 tasks by specifying +- + task1 - | task2 - +- +where the vertical bar is the Unix piping symbol. This assumes that the 2 +tasks read the name of the FITS file off of the command line. + +**C. Output File Name when Opening an Existing File + +An optional output filename may be specified in parentheses immediately +following the base file name to be opened. This is mainly useful in +those cases where CFITSIO creates a temporary copy of the input FITS +file before it is opened and passed to the application program. This +happens by default when opening a network FTP or HTTP-type file, when +reading a compressed FITS file on a local disk, when reading from the +stdin stream, or when a column filter, row filter, or binning specifier +is included as part of the input file specification. By default this +temporary file is created in memory. If there is not enough memory to +create the file copy, then CFITSIO will exit with an error. In these +cases one can force a permanent file to be created on disk, instead of +a temporary file in memory, by supplying the name in parentheses +immediately following the base file name. The output filename can +include the '!' clobber flag. + +Thus, if the input filename to CFITSIO is: +\verb+file1.fits.gz(file2.fits)+ +then CFITSIO will uncompress `file1.fits.gz' into the local disk file +`file2.fits' before opening it. CFITSIO does not automatically delete +the output file, so it will still exist after the application program +exits. + +The output filename "mem://" is also allowed, which will write the +output file into memory, and also allow write access to the file. This +'file' will disappear when it is closed, but this may be useful for +some applications which only need to modify a temporary copy of the file. + +In some cases, several different temporary FITS files will be created +in sequence, for instance, if one opens a remote file using FTP, then +filters rows in a binary table extension, then create an image by +binning a pair of columns. In this case, the remote file will be +copied to a temporary local file, then a second temporary file will be +created containing the filtered rows of the table, and finally a third +temporary file containing the binned image will be created. In cases +like this where multiple files are created, the outfile specifier will +be interpreted the name of the final file as described below, in descending +priority: + +\begin{itemize} +\item +as the name of the final image file if an image within a single binary +table cell is opened or if an image is created by binning a table column. +\item +as the name of the file containing the filtered table if a column filter +and/or a row filter are specified. +\item +as the name of the local copy of the remote FTP or HTTP file. +\item +as the name of the uncompressed version of the FITS file, if a +compressed FITS file on local disk has been opened. +\item +otherwise, the output filename is ignored. +\end{itemize} + +The output file specifier is useful when reading FTP or HTTP-type +FITS files since it can be used to create a local disk copy of the file +that can be reused in the future. If the output file name = `*' then a +local file with the same name as the network file will be created. +Note that CFITSIO will behave differently depending on whether the +remote file is compressed or not as shown by the following examples: +\begin{itemize} +\item +\verb+ftp://remote.machine/tmp/myfile.fits.gz(*)+ - the remote compressed +file is copied to the local compressed file `myfile.fits.gz', which +is then uncompressed in local memory before being opened and passed +to the application program. + +\item +\verb+ftp://remote.machine/tmp/myfile.fits.gz(myfile.fits)+ - the +remote compressed file is copied and uncompressed into the local file +`myfile.fits'. This example requires less local memory than the +previous example since the file is uncompressed on disk instead of in +memory. + +\item +\verb+ftp://remote.machine/tmp/myfile.fits(myfile.fits.gz)+ - this will +usually produce an error since CFITSIO itself cannot compress files. +\end{itemize} + +The exact behavior of CFITSIO in the latter case depends on the type of +ftp server running on the remote machine and how it is configured. In +some cases, if the file `myfile.fits.gz' exists on the remote machine, +then the server will copy it to the local machine. In other cases the +ftp server will automatically create and transmit a compressed version +of the file if only the uncompressed version exists. This can get +rather confusing, so users should use a certain amount of caution when +using the output file specifier with FTP or HTTP file types, to make +sure they get the behavior that they expect. + +**D. Template File Name when Creating a New File + +When a new FITS file is created with a call to fits\_create\_file, the +name of a template file may be supplied in parentheses immediately +following the name of the new file to be created. This template is +used to define the structure of one or more HDUs in the new file. The +template file may be another FITS file, in which case the newly created +file will have exactly the same keywords in each HDU as in the template +FITS file, but all the data units will be filled with zeros. The +template file may also be an ASCII text file, where each line (in +general) describes one FITS keyword record. The format of the ASCII +template file is described in the following Template Files chapter. + +**E. Image Tile-Compression Specification + +When specifying the name of the output FITS file to be created, the +user can indicate that images should be written in tile-compressed +format (see section 5.5, ``Primary Array or IMAGE Extension I/O +Routines'') by enclosing the compression parameters in square brackets +following the root disk file name. Here are some examples of the +syntax for specifying tile-compressed output images: +- + myfile.fit[compress] - use Rice algorithm and default tile size + + myfile.fit[compress GZIP] - use the specified compression algorithm; + myfile.fit[compress Rice] only the first letter of the algorithm + myfile.fit[compress PLIO] name is required. + + myfile.fit[compress Rice 100,100] - use 100 x 100 pixel tile size + myfile.fit[compress Rice 100,100;2] - as above, and use noisebits = 2 +- + +**F. HDU Location Specification + +The optional HDU location specifier defines which HDU (Header-Data +Unit, also known as an `extension') within the FITS file to initially +open. It must immediately follow the base file name (or the output +file name if present). If it is not specified then the first HDU (the +primary array) is opened. The HDU location specifier is required if +the colFilter, rowFilter, or binSpec specifiers are present, because +the primary array is not a valid HDU for these operations. The HDU may +be specified either by absolute position number, starting with 0 for +the primary array, or by reference to the HDU name, and optionally, the +version number and the HDU type of the desired extension. The location +of an image within a single cell of a binary table may also be +specified, as described below. + +The absolute position of the extension is specified either by enclosed +the number in square brackets (e.g., `[1]' = the first extension +following the primary array) or by preceded the number with a plus sign +(`+1'). To specify the HDU by name, give the name of the desired HDU +(the value of the EXTNAME or HDUNAME keyword) and optionally the +extension version number (value of the EXTVER keyword) and the +extension type (value of the XTENSION keyword: IMAGE, ASCII or TABLE, +or BINTABLE), separated by commas and all enclosed in square brackets. +If the value of EXTVER and XTENSION are not specified, then the first +extension with the correct value of EXTNAME is opened. The extension +name and type are not case sensitive, and the extension type may be +abbreviated to a single letter (e.g., I = IMAGE extension or primary +array, A or T = ASCII table extension, and B = binary table BINTABLE +extension). If the HDU location specifier is equal to `[PRIMARY]' or +`[P]', then the primary array (the first HDU) will be opened. + +An optional pound sign character ("\#") may be appended to the extension +name or number to signify that any other extensions in the file should +be ignored during any subsequent file filtering operations. For example, +when doing row filtering operations on a table extension, CFITSIO normally +creates a copy of the filtered table in memory, along with a verbatim +copy of all the other extensions in the input FITS file. If the pound +sign is appended to the table extension name, then only that extension, +and none of the other extensions in the file, will by copied to memory, +as in the following example: +- + myfile.fit[events#][TIME > 10000] +- + +FITS images are most commonly stored in the primary array or an image +extension, but images can also be stored as a vector in a single cell +of a binary table (i.e. each row of the vector column contains a +different image). Such an image can be opened with CFITSIO by +specifying the desired column name and the row number after the binary +table HDU specifier as shown in the following examples. The column name +is separated from the HDU specifier by a semicolon and the row number +is enclosed in parentheses. In this case CFITSIO copies the image from +the table cell into a temporary primary array before it is opened. The +application program then just sees the image in the primary array, +without any extensions. The particular row to be opened may be +specified either by giving an absolute integer row number (starting +with 1 for the first row), or by specifying a boolean expression that +evaluates to TRUE for the desired row. The first row that satisfies +the expression will be used. The row selection expression has the same +syntax as described in the Row Filter Specifier section, below. + + Examples: +- + myfile.fits[3] - open the 3rd HDU following the primary array + myfile.fits+3 - same as above, but using the FTOOLS-style notation + myfile.fits[EVENTS] - open the extension that has EXTNAME = 'EVENTS' + myfile.fits[EVENTS, 2] - same as above, but also requires EXTVER = 2 + myfile.fits[events,2,b] - same, but also requires XTENSION = 'BINTABLE' + myfile.fits[3; images(17)] - opens the image in row 17 of the 'images' + column in the 3rd extension of the file. + myfile.fits[3; images(exposure > 100)] - as above, but opens the image + in the first row that has an 'exposure' column value + greater than 100. +- + +**G. Image Section + +A virtual file containing a rectangular subsection of an image can be +extracted and opened by specifying the range of pixels (start:end) +along each axis to be extracted from the original image. One can also +specify an optional pixel increment (start:end:step) for each axis of +the input image. A pixel step = 1 will be assumed if it is not +specified. If the start pixel is larger then the end pixel, then the +image will be flipped (producing a mirror image) along that dimension. +An asterisk, '*', may be used to specify the entire range of an axis, +and '-*' will flip the entire axis. The input image can be in the +primary array, in an image extension, or contained in a vector cell of +a binary table. In the later 2 cases the extension name or number must +be specified before the image section specifier. + + Examples: +- + myfile.fits[1:512:2, 2:512:2] - open a 256x256 pixel image + consisting of the odd numbered columns (1st axis) and + the even numbered rows (2nd axis) of the image in the + primary array of the file. + + myfile.fits[*, 512:256] - open an image consisting of all the columns + in the input image, but only rows 256 through 512. + The image will be flipped along the 2nd axis since + the starting pixel is greater than the ending pixel. + + myfile.fits[*:2, 512:256:2] - same as above but keeping only + every other row and column in the input image. + + myfile.fits[-*, *] - copy the entire image, flipping it along + the first axis. + + myfile.fits[3][1:256,1:256] - opens a subsection of the image that + is in the 3rd extension of the file. + + myfile.fits[4; images(12)][1:10,1:10] - open an image consisting + of the first 10 pixels in both dimensions. The original + image resides in the 12th row of the 'images' vector + column in the table in the 4th extension of the file. +- + +When CFITSIO opens an image section it first creates a temporary file +containing the image section plus a copy of any other HDUs in the +file. (If a `\#' character is appended to the name or number of the +image HDU, as in "myfile.fits[1\#][1:200,1:200]", then the other +HDUs in the input file will not be copied into memory). +This temporary file is then opened by the application program, +so it is not possible to write to or modify the input file when +specifying an image section. Note that CFITSIO automatically updates +the world coordinate system keywords in the header of the image +section, if they exist, so that the coordinate associated with each +pixel in the image section will be computed correctly. + +**H. Image Transform Filters + +CFITSIO can apply a user-specified mathematical function to the value +of every pixel in a FITS image, thus creating a new virtual image +in computer memory that is then opened and read by the application +program. The original FITS image is not modified by this process. + +The image transformation specifier is appended to the input +FITS file name and is enclosed in square brackets. It begins with the +letters 'PIX' to distinguish it from other types of FITS file filters +that are recognized by CFITSIO. The image transforming function may +use any of the mathematical operators listed in the following +'Row Filtering Specification' section of this document. +Some examples of image transform filters are: +- + [pix X * 2.0] - multiply each pixel by 2.0 + [pix sqrt(X)] - take the square root of each pixel + [pix X + #ZEROPT - add the value of the ZEROPT keyword + [pix X>0 ? log10(X) : -99.] - if the pixel value is greater + than 0, compute the base 10 log, + else set the pixel = -99. +- +Use the letter 'X' in the expression to represent the current pixel value +in the image. The expression is evaluated +independently for each pixel in the image and may be a function of 1) the +original pixel value, 2) the value of other pixels in the image at +a given relative offset from the position of the pixel that is being +evaluated, and 3) the value of +any header keywords. Header keyword values are represented +by the name of the keyword preceded by the '\#' sign. + + +To access the the value of adjacent pixels in the image, +specify the (1-D) offset from the current pixel in curly brackets. +For example +- + [pix (x{-1} + x + x{+1}) / 3] +- +will replace each pixel value with the running mean of the values of that +pixel and it's 2 neighboring pixels. Note that in this notation the image +is treated as a 1-D array, where each row of the image (or higher dimensional +cube) is appended one after another in one long array of pixels. +It is possible to refer to pixels +in the rows above or below the current pixel by using the value of the +NAXIS1 header keyword. For example +- + [pix (x{-#NAXIS1} + x + x{#NAXIS1}) / 3] +- +will compute the mean of each image pixel and the pixels immediately +above and below it in the adjacent rows of the image. +The following more complex example +creates a smoothed virtual image where each pixel +is a 3 x 3 boxcar average of the input image pixels: +- + [pix (X + X{-1} + X{+1} + + X{-#NAXIS1} + X{-#NAXIS1 - 1} + X{-#NAXIS1 + 1} + + X{#NAXIS1} + X{#NAXIS1 - 1} + X{#NAXIS1 + 1}) / 9.] +- +If the pixel offset +extends beyond the first or last pixel in the image, the function will +evaluate to undefined, or NULL. + +For complex or commonly used image filtering operations, +one can write the expression into an external text file and +then import it into the +filter using the syntax '[pix @filename.txt]'. The mathematical +expression can +extend over multiple lines of text in the file. +Any lines in the external text file +that begin with 2 slash characters ('//') will be ignored and may be +used to add comments into the file. + +By default, the datatype of the resulting image will be the same as +the original image, but one may force a different datatype by appended +a code letter to the 'pix' keyword: +- + pixb - 8-bit byte image with BITPIX = 8 + pixi - 16-bit integer image with BITPIX = 16 + pixj - 32-bit integer image with BITPIX = 32 + pixr - 32-bit float image with BITPIX = -32 + pixd - 64-bit float image with BITPIX = -64 +- +Also by default, any other HDUs in the input file will be copied without +change to the +output virtual FITS file, but one may discard the other HDUs by adding +the number '1' to the 'pix' keyword (and following any optional datatype code +letter). For example: +- + myfile.fits[3][pixr1 sqrt(X)] +- +will create a virtual FITS file containing only a primary array image +with 32-bit floating point pixels that have a value equal to the square +root of the pixels in the image that is in the 3rd extension +of the 'myfile.fits' file. + + +**I. Column and Keyword Filtering Specification + +The optional column/keyword filtering specifier is used to modify the +column structure and/or the header keywords in the HDU that was +selected with the previous HDU location specifier. This filtering +specifier must be enclosed in square brackets and can be distinguished +from a general row filter specifier (described below) by the fact that +it begins with the string 'col ' and is not immediately followed by an +equals sign. The original file is not changed by this filtering +operation, and instead the modifications are made on a copy of the +input FITS file (usually in memory), which also contains a copy of all +the other HDUs in the file. (If a `\#' character is appended to the name +or number of the +table HDU then only the primary array, and none of the other +HDUs in the input file will be copied into memory). +This temporary file is passed to the +application program and will persist only until the file is closed or +until the program exits, unless the outfile specifier (see above) is +also supplied. + +The column/keyword filter can be used to perform the following +operations. More than one operation may be specified by separating +them with commas or semi-colons. + +\begin{itemize} + +\item +Copy only a specified list of columns columns to the filtered input file. +The list of column name should be separated by semi-colons. Wild card +characters may be used in the column names to match multiple columns. +If the expression contains both a list of columns to be included and +columns to be deleted, then all the columns in the original table +except the explicitly deleted columns will appear in the filtered +table (i.e., there is no need to explicitly list the columns to +be included if any columns are being deleted). + +\item +Delete a column or keyword by listing the name preceded by a minus sign +or an exclamation mark (!), e.g., '-TIME' will delete the TIME column +if it exists, otherwise the TIME keyword. An error is returned if +neither a column nor keyword with this name exists. Note that the +exclamation point, '!', is a special UNIX character, so if it is used +on the command line rather than entered at a task prompt, it must be +preceded by a backslash to force the UNIX shell to ignore it. + +\item +Rename an existing column or keyword with the syntax 'NewName == +OldName'. An error is returned if neither a column nor keyword with +this name exists. + +\item +Append a new column or keyword to the table. To create a column, +give the new name, optionally followed by the data type in parentheses, +followed by a single equals sign and an expression to be used to +compute the value (e.g., 'newcol(1J) = 0' will create a new 32-bit +integer column called 'newcol' filled with zeros). The data type is +specified using the same syntax that is allowed for the value of the +FITS TFORMn keyword (e.g., 'I', 'J', 'E', 'D', etc. for binary tables, +and 'I8', F12.3', 'E20.12', etc. for ASCII tables). If the data type is +not specified then an appropriate data type will be chosen depending on +the form of the expression (may be a character string, logical, bit, long +integer, or double column). An appropriate vector count (in the case +of binary tables) will also be added if not explicitly specified. + +When creating a new keyword, the keyword name must be preceded by a +pound sign '\#', and the expression must evaluate to a scalar +(i.e., cannot have a column name in the expression). The comment +string for the keyword may be specified in parentheses immediately +following the keyword name (instead of supplying a data type as in +the case of creating a new column). If the keyword name ends with a +pound sign '\#', then cfitsio will substitute the number of the +most recently referenced column for the \# character . +This is especially useful when writing +a column-related keyword like TUNITn for a newly created column, +as shown in the following examples. + +\item +Recompute (overwrite) the values in an existing column or keyword by +giving the name followed by an equals sign and an arithmetic +expression. +\end{itemize} + +The expression that is used when appending or recomputing columns or +keywords can be arbitrarily complex and may be a function of other +header keyword values and other columns (in the same row). The full +syntax and available functions for the expression are described below +in the row filter specification section. + +If the expression contains both a list of columns to be included and +columns to be deleted, then all the columns in the original table +except the explicitly deleted columns will appear in the filtered +table. If no columns to be deleted are specified, then only the +columns that are explicitly listed will be included in the filtered +output table. To include all the columns, add the '*' wildcard +specifier at the end of the list, as shown in the examples. + +For complex or commonly used operations, one can place the +operations into an external text file and import it into the column +filter using the syntax '[col @filename.txt]'. The operations can +extend over multiple lines of the file, but multiple operations must +still be separated by semicolons. Any lines in the external text file +that begin with 2 slash characters ('//') will be ignored and may be +used to add comments into the file. + +Examples: +- + [col Time; rate] - only the Time and rate columns will + appear in the filtered input file. + + [col Time, *raw] - include the Time column and any other + columns whose name ends with 'raw'. + + [col -TIME; Good == STATUS] - deletes the TIME column and + renames the status column to 'Good' + + [col PI=PHA * 1.1 + 0.2; #TUNIT#(column units) = 'counts';*] + - creates new PI column from PHA values + and also writes the TUNITn keyword + for the new column. The final '*' + expression means preserve all the + columns in the input table in the + virtual output table; without the '*' + the output table would only contain + the single 'PI' column. + + [col rate = rate/exposure; TUNIT#(&) = 'counts/s';*] + - recomputes the rate column by dividing + it by the EXPOSURE keyword value. This + also modifies the value of the TUNITn + keyword for this column. The use of the + '&' character for the keyword comment + string means preserve the existing + comment string for that keyword. The + final '*' preserves all the columns + in the input table in the virtual + output table. +- + +**J. Row Filtering Specification + + When entering the name of a FITS table that is to be opened by a + program, an optional row filter may be specified to select a subset + of the rows in the table. A temporary new FITS file is created on + the fly which contains only those rows for which the row filter + expression evaluates to true. The primary array and any other + extensions in the input file are also copied to the temporary + file. +(If a `\#' character is appended to the name +or number of the +table HDU then only the primary array, and none of the other +HDUs in the input file will be copied into the temporary file). + The original FITS file is closed and the new virtual file + is opened by the application program. The row filter expression is + enclosed in square brackets following the file name and extension + name (e.g., 'file.fits[events][GRADE==50]' selects only those rows + where the GRADE column value equals 50). When dealing with tables + where each row has an associated time and/or 2D spatial position, + the row filter expression can also be used to select rows based on + the times in a Good Time Intervals (GTI) extension, or on spatial + position as given in a SAO-style region file. + +***1. General Syntax + + The row filtering expression can be an arbitrarily complex series + of operations performed on constants, keyword values, and column + data taken from the specified FITS TABLE extension. The expression + must evaluate to a boolean value for each row of the table, where + a value of FALSE means that the row will be excluded. + + For complex or commonly used filters, one can place the expression + into a text file and import it into the row filter using the syntax + '[@filename.txt]'. The expression can be arbitrarily complex and + extend over multiple lines of the file. Any lines in the external + text file that begin with 2 slash characters ('//') will be ignored + and may be used to add comments into the file. + + Keyword and column data are referenced by name. Any string of + characters not surrounded by quotes (ie, a constant string) or + followed by an open parentheses (ie, a function name) will be + initially interpreted as a column name and its contents for the + current row inserted into the expression. If no such column exists, + a keyword of that name will be searched for and its value used, if + found. To force the name to be interpreted as a keyword (in case + there is both a column and keyword with the same name), precede the + keyword name with a single pound sign, '\#', as in '\#NAXIS2'. Due to + the generalities of FITS column and keyword names, if the column or + keyword name contains a space or a character which might appear as + an arithmetic term then enclose the name in '\$' characters as in + \$MAX PHA\$ or \#\$MAX-PHA\$. Names are case insensitive. + + To access a table entry in a row other than the current one, follow + the column's name with a row offset within curly braces. For + example, 'PHA\{-3\}' will evaluate to the value of column PHA, 3 rows + above the row currently being processed. One cannot specify an + absolute row number, only a relative offset. Rows that fall outside + the table will be treated as undefined, or NULLs. + + Boolean operators can be used in the expression in either their + Fortran or C forms. The following boolean operators are available: +- + "equal" .eq. .EQ. == "not equal" .ne. .NE. != + "less than" .lt. .LT. < "less than/equal" .le. .LE. <= =< + "greater than" .gt. .GT. > "greater than/equal" .ge. .GE. >= => + "or" .or. .OR. || "and" .and. .AND. && + "negation" .not. .NOT. ! "approx. equal(1e-7)" ~ +- + +Note that the exclamation +point, '!', is a special UNIX character, so if it is used on the +command line rather than entered at a task prompt, it must be preceded +by a backslash to force the UNIX shell to ignore it. + + The expression may also include arithmetic operators and functions. + Trigonometric functions use radians, not degrees. The following + arithmetic operators and functions can be used in the expression + (function names are case insensitive). A null value will be returned + in case of illegal operations such as divide by zero, sqrt(negative) + log(negative), log10(negative), arccos(.gt. 1), arcsin(.gt. 1). + +- + "addition" + "subtraction" - + "multiplication" * "division" / + "negation" - "exponentiation" ** ^ + "absolute value" abs(x) "cosine" cos(x) + "sine" sin(x) "tangent" tan(x) + "arc cosine" arccos(x) "arc sine" arcsin(x) + "arc tangent" arctan(x) "arc tangent" arctan2(y,x) + "hyperbolic cos" cosh(x) "hyperbolic sin" sinh(x) + "hyperbolic tan" tanh(x) "round to nearest int" round(x) + "round down to int" floor(x) "round up to int" ceil(x) + "exponential" exp(x) "square root" sqrt(x) + "natural log" log(x) "common log" log10(x) + "modulus" x % y "random # [0.0,1.0)" random() + "random Gaussian" randomn() "random Poisson" randomp(x) + "minimum" min(x,y) "maximum" max(x,y) + "cumulative sum" accum(x) "sequential difference" seqdiff(x) + "if-then-else" b?x:y + "angular separation" angsep(ra1,dec1,ra2,de2) (all in degrees) + "substring" strmid(s,p,n) "string search" strstr(s,r) +- +Three different random number functions are provided: random(), with +no arguments, produces a uniform random deviate between 0 and 1; +randomn(), also with no arguments, produces a normal (Gaussian) random +deviate with zero mean and unit standard deviation; randomp(x) +produces a Poisson random deviate whose expected number of counts is +X. X may be any positive real number of expected counts, including +fractional values, but the return value is an integer. + +When the random functions are used in a vector expression, by default +the same random value will be used when evaluating each element of the vector. +If different random numbers are desired, then the name of a vector +column should be supplied as the single argument to the random +function (e.g., "flux + 0.1 * random(flux)", where "flux' is the +name of a vector column). This will create a vector of +random numbers that will be used in sequence when evaluating each +element of the vector expression. + +An alternate syntax for the min and max functions has only a single +argument which should be a vector value (see below). The result +will be the minimum/maximum element contained within the vector. + +The accum(x) function forms the cumulative sum of x, element by element. +Vector columns are supported simply by performing the summation process +through all the values. Null values are treated as 0. The seqdiff(x) +function forms the sequential difference of x, element by element. +The first value of seqdiff is the first value of x. A single null +value in x causes a pair of nulls in the output. The seqdiff and +accum functions are functional inverses, i.e., seqdiff(accum(x)) == x +as long as no null values are present. + +In the if-then-else expression, "b?x:y", b is an explicit boolean +value or expression. There is no automatic type conversion from +numeric to boolean values, so one needs to use "iVal!=0" instead of +merely "iVal" as the boolean argument. x and y can be any scalar data +type (including string). + +The angsep function computes the angular separation in degrees +between 2 celestial positions, where the first 2 parameters +give the RA-like and Dec-like coordinates (in decimal degrees) +of the first position, and the 3rd and 4th parameters give the +coordinates of the second position. + +The substring function strmid(S,P,N) extracts a substring from S, +starting at string position P, with a substring length N. The first +character position in S is labeled as 1. If P is 0, or refers to a +position beyond the end of S, then the extracted substring will be +NULL. S, P, and N may be functions of other columns. + +The string search function strstr(S,R) searches for the first occurrence +of the substring R in S. The result is an integer, indicating the +character position of the first match (where 1 is the first character +position of S). If no match is found, then strstr() returns a NULL +value. + +The following type casting operators are available, where the +inclosing parentheses are required and taken from the C language +usage. Also, the integer to real casts values to double precision: +- + "real to integer" (int) x (INT) x + "integer to real" (float) i (FLOAT) i +- + + In addition, several constants are built in for use in numerical + expressions: + +- + #pi 3.1415... #e 2.7182... + #deg #pi/180 #row current row number + #null undefined value #snull undefined string +- + + A string constant must be enclosed in quotes as in 'Crab'. The + "null" constants are useful for conditionally setting table values + to a NULL, or undefined, value (eg., "col1==-99 ? \#NULL : col1"). + + There is also a function for testing if two values are close to + each other, i.e., if they are "near" each other to within a user + specified tolerance. The arguments, value\_1 and value\_2 can be + integer or real and represent the two values who's proximity is + being tested to be within the specified tolerance, also an integer + or real: +- + near(value_1, value_2, tolerance) +- + When a NULL, or undefined, value is encountered in the FITS table, + the expression will evaluate to NULL unless the undefined value is + not actually required for evaluation, e.g. "TRUE .or. NULL" + evaluates to TRUE. The following two functions allow some NULL + detection and handling: +- + "a null value?" ISNULL(x) + "define a value for null" DEFNULL(x,y) +- + The former + returns a boolean value of TRUE if the argument x is NULL. The + later "defines" a value to be substituted for NULL values; it + returns the value of x if x is not NULL, otherwise it returns the + value of y. + + + +***2. Bit Masks + + Bit masks can be used to select out rows from bit columns (TFORMn = + \#X) in FITS files. To represent the mask, binary, octal, and hex + formats are allowed: + +- + binary: b0110xx1010000101xxxx0001 + octal: o720x1 -> (b111010000xxx001) + hex: h0FxD -> (b00001111xxxx1101) +- + + In all the representations, an x or X is allowed in the mask as a + wild card. Note that the x represents a different number of wild + card bits in each representation. All representations are case + insensitive. + + To construct the boolean expression using the mask as the boolean + equal operator described above on a bit table column. For example, + if you had a 7 bit column named flags in a FITS table and wanted + all rows having the bit pattern 0010011, the selection expression + would be: + +- + flags == b0010011 + or + flags .eq. b10011 +- + + It is also possible to test if a range of bits is less than, less + than equal, greater than and greater than equal to a particular + boolean value: + +- + flags <= bxxx010xx + flags .gt. bxxx100xx + flags .le. b1xxxxxxx +- + + Notice the use of the x bit value to limit the range of bits being + compared. + + It is not necessary to specify the leading (most significant) zero + (0) bits in the mask, as shown in the second expression above. + + Bit wise AND, OR and NOT operations are also possible on two or + more bit fields using the '\&'(AND), '$|$'(OR), and the '!'(NOT) + operators. All of these operators result in a bit field which can + then be used with the equal operator. For example: + +- + (!flags) == b1101100 + (flags & b1000001) == bx000001 +- + + Bit fields can be appended as well using the '+' operator. Strings + can be concatenated this way, too. + +***3. Vector Columns + + Vector columns can also be used in building the expression. No + special syntax is required if one wants to operate on all elements + of the vector. Simply use the column name as for a scalar column. + Vector columns can be freely intermixed with scalar columns or + constants in virtually all expressions. The result will be of the + same dimension as the vector. Two vectors in an expression, though, + need to have the same number of elements and have the same + dimensions. + + Arithmetic and logical operations are all performed on an element by + element basis. Comparing two vector columns, eg "COL1 == COL2", + thus results in another vector of boolean values indicating which + elements of the two vectors are equal. + + Eight functions are available that operate on a vector and return a + scalar result: +- + "minimum" MIN(V) "maximum" MAX(V) + "average" AVERAGE(V) "median" MEDIAN(V) + "summation" SUM(V) "standard deviation" STDDEV(V) + "# of values" NELEM(V) "# of non-null values" NVALID(V) +- + where V represents the name of a vector column or a manually + constructed vector using curly brackets as described below. The + first 6 of these functions ignore any null values in the vector when + computing the result. The STDDEV() function computes the sample + standard deviation, i.e. it is proportional to 1/SQRT(N-1) instead + of 1/SQRT(N), where N is NVALID(V). + + The SUM function literally sums all the elements in x, returning a + scalar value. If V is a boolean vector, SUM returns the number + of TRUE elements. The NELEM function returns the number of elements + in vector V whereas NVALID return the number of non-null elements in + the vector. (NELEM also operates on bit and string columns, + returning their column widths.) As an example, to test whether all + elements of two vectors satisfy a given logical comparison, one can + use the expression +- + SUM( COL1 > COL2 ) == NELEM( COL1 ) +- + + which will return TRUE if all elements of COL1 are greater than + their corresponding elements in COL2. + + To specify a single element of a vector, give the column name + followed by a comma-separated list of coordinates enclosed in + square brackets. For example, if a vector column named PHAS exists + in the table as a one dimensional, 256 component list of numbers + from which you wanted to select the 57th component for use in the + expression, then PHAS[57] would do the trick. Higher dimensional + arrays of data may appear in a column. But in order to interpret + them, the TDIMn keyword must appear in the header. Assuming that a + (4,4,4,4) array is packed into each row of a column named ARRAY4D, + the (1,2,3,4) component element of each row is accessed by + ARRAY4D[1,2,3,4]. Arrays up to dimension 5 are currently + supported. Each vector index can itself be an expression, although + it must evaluate to an integer value within the bounds of the + vector. Vector columns which contain spaces or arithmetic operators + must have their names enclosed in "\$" characters as with + \$ARRAY-4D\$[1,2,3,4]. + + A more C-like syntax for specifying vector indices is also + available. The element used in the preceding example alternatively + could be specified with the syntax ARRAY4D[4][3][2][1]. Note the + reverse order of indices (as in C), as well as the fact that the + values are still ones-based (as in Fortran -- adopted to avoid + ambiguity for 1D vectors). With this syntax, one does not need to + specify all of the indices. To extract a 3D slice of this 4D + array, use ARRAY4D[4]. + + Variable-length vector columns are not supported. + + Vectors can be manually constructed within the expression using a + comma-separated list of elements surrounded by curly braces ('\{\}'). + For example, '\{1,3,6,1\}' is a 4-element vector containing the values + 1, 3, 6, and 1. The vector can contain only boolean, integer, and + real values (or expressions). The elements will be promoted to the + highest data type present. Any elements which are themselves + vectors, will be expanded out with each of its elements becoming an + element in the constructed vector. + +***4. Good Time Interval Filtering + + A common filtering method involves selecting rows which have a time + value which lies within what is called a Good Time Interval or GTI. + The time intervals are defined in a separate FITS table extension + which contains 2 columns giving the start and stop time of each + good interval. The filtering operation accepts only those rows of + the input table which have an associated time which falls within + one of the time intervals defined in the GTI extension. A high + level function, gtifilter(a,b,c,d), is available which evaluates + each row of the input table and returns TRUE or FALSE depending + whether the row is inside or outside the good time interval. The + syntax is +- + gtifilter( [ "gtifile" [, expr [, "STARTCOL", "STOPCOL" ] ] ] ) + or + gtifilter( [ 'gtifile' [, expr [, 'STARTCOL', 'STOPCOL' ] ] ] ) +- + where each "[]" demarks optional parameters. Note that the quotes + around the gtifile and START/STOP column are required. Either single + or double quotes may be used. In cases where this expression is + entered on the Unix command line, enclose the entire expression in + double quotes, and then use single quotes within the expression to + enclose the 'gtifile' and other terms. It is also usually possible + to do the reverse, and enclose the whole expression in single quotes + and then use double quotes within the expression. The gtifile, + if specified, can be blank ("") which will mean to use the first + extension with the name "*GTI*" in the current file, a plain + extension specifier (eg, "+2", "[2]", or "[STDGTI]") which will be + used to select an extension in the current file, or a regular + filename with or without an extension specifier which in the latter + case will mean to use the first extension with an extension name + "*GTI*". Expr can be any arithmetic expression, including simply + the time column name. A vector time expression will produce a + vector boolean result. STARTCOL and STOPCOL are the names of the + START/STOP columns in the GTI extension. If one of them is + specified, they both must be. + + In its simplest form, no parameters need to be provided -- default + values will be used. The expression "gtifilter()" is equivalent to +- + gtifilter( "", TIME, "*START*", "*STOP*" ) +- + This will search the current file for a GTI extension, filter the + TIME column in the current table, using START/STOP times taken from + columns in the GTI extension with names containing the strings + "START" and "STOP". The wildcards ('*') allow slight variations in + naming conventions such as "TSTART" or "STARTTIME". The same + default values apply for unspecified parameters when the first one + or two parameters are specified. The function automatically + searches for TIMEZERO/I/F keywords in the current and GTI + extensions, applying a relative time offset, if necessary. + +***5. Spatial Region Filtering + + Another common filtering method selects rows based on whether the + spatial position associated with each row is located within a given + 2-dimensional region. The syntax for this high-level filter is +- + regfilter( "regfilename" [ , Xexpr, Yexpr [ , "wcs cols" ] ] ) +- + where each "[]" demarks optional parameters. The region file name + is required and must be enclosed in quotes. The remaining + parameters are optional. There are 2 supported formats for the + region file: ASCII file or FITS binary table. The region file + contains a list of one or more geometric shapes (circle, + ellipse, box, etc.) which defines a region on the celestial sphere + or an area within a particular 2D image. The region file is + typically generated using an image display program such as fv/POW + (distribute by the HEASARC), or ds9 (distributed by the Smithsonian + Astrophysical Observatory). Users should refer to the documentation + provided with these programs for more details on the syntax used in + the region files. The FITS region file format is defined in a document + available from the FITS Support Office at + http://fits.gsfc.nasa.gov/ registry/ region.html + + In its simplest form, (e.g., regfilter("region.reg") ) the + coordinates in the default 'X' and 'Y' columns will be used to + determine if each row is inside or outside the area specified in + the region file. Alternate position column names, or expressions, + may be entered if needed, as in +- + regfilter("region.reg", XPOS, YPOS) +- + Region filtering can be applied most unambiguously if the positions + in the region file and in the table to be filtered are both give in + terms of absolute celestial coordinate units. In this case the + locations and sizes of the geometric shapes in the region file are + specified in angular units on the sky (e.g., positions given in + R.A. and Dec. and sizes in arcseconds or arcminutes). Similarly, + each row of the filtered table will have a celestial coordinate + associated with it. This association is usually implemented using + a set of so-called 'World Coordinate System' (or WCS) FITS keywords + that define the coordinate transformation that must be applied to + the values in the 'X' and 'Y' columns to calculate the coordinate. + + Alternatively, one can perform spatial filtering using unitless + 'pixel' coordinates for the regions and row positions. In this + case the user must be careful to ensure that the positions in the 2 + files are self-consistent. A typical problem is that the region + file may be generated using a binned image, but the unbinned + coordinates are given in the event table. The ROSAT events files, + for example, have X and Y pixel coordinates that range from 1 - + 15360. These coordinates are typically binned by a factor of 32 to + produce a 480x480 pixel image. If one then uses a region file + generated from this image (in image pixel units) to filter the + ROSAT events file, then the X and Y column values must be converted + to corresponding pixel units as in: +- + regfilter("rosat.reg", X/32.+.5, Y/32.+.5) +- + Note that this binning conversion is not necessary if the region + file is specified using celestial coordinate units instead of pixel + units because CFITSIO is then able to directly compare the + celestial coordinate of each row in the table with the celestial + coordinates in the region file without having to know anything + about how the image may have been binned. + + The last "wcs cols" parameter should rarely be needed. If supplied, + this string contains the names of the 2 columns (space or comma + separated) which have the associated WCS keywords. If not supplied, + the filter will scan the X and Y expressions for column names. + If only one is found in each expression, those columns will be + used, otherwise an error will be returned. + + These region shapes are supported (names are case insensitive): +- + Point ( X1, Y1 ) <- One pixel square region + Line ( X1, Y1, X2, Y2 ) <- One pixel wide region + Polygon ( X1, Y1, X2, Y2, ... ) <- Rest are interiors with + Rectangle ( X1, Y1, X2, Y2, A ) | boundaries considered + Box ( Xc, Yc, Wdth, Hght, A ) V within the region + Diamond ( Xc, Yc, Wdth, Hght, A ) + Circle ( Xc, Yc, R ) + Annulus ( Xc, Yc, Rin, Rout ) + Ellipse ( Xc, Yc, Rx, Ry, A ) + Elliptannulus ( Xc, Yc, Rinx, Riny, Routx, Routy, Ain, Aout ) + Sector ( Xc, Yc, Amin, Amax ) +- + where (Xc,Yc) is the coordinate of the shape's center; (X\#,Y\#) are + the coordinates of the shape's edges; Rxxx are the shapes' various + Radii or semimajor/minor axes; and Axxx are the angles of rotation + (or bounding angles for Sector) in degrees. For rotated shapes, the + rotation angle can be left off, indicating no rotation. Common + alternate names for the regions can also be used: rotbox = box; + rotrectangle = rectangle; (rot)rhombus = (rot)diamond; and pie + = sector. When a shape's name is preceded by a minus sign, '-', + the defined region is instead the area *outside* its boundary (ie, + the region is inverted). All the shapes within a single region + file are OR'd together to create the region, and the order is + significant. The overall way of looking at region files is that if + the first region is an excluded region then a dummy included region + of the whole detector is inserted in the front. Then each region + specification as it is processed overrides any selections inside of + that region specified by previous regions. Another way of thinking + about this is that if a previous excluded region is completely + inside of a subsequent included region the excluded region is + ignored. + + The positional coordinates may be given either in pixel units, + decimal degrees or hh:mm:ss.s, dd:mm:ss.s units. The shape sizes + may be given in pixels, degrees, arcminutes, or arcseconds. Look + at examples of region file produced by fv/POW or ds9 for further + details of the region file format. + + There are three low-level functions that are primarily for use with + regfilter function, but they can be called directly. They + return a boolean true or false depending on whether a two + dimensional point is in the region or not. The positional coordinates + must be given in pixel units: +- + "point in a circular region" + circle(xcntr,ycntr,radius,Xcolumn,Ycolumn) + + "point in an elliptical region" + ellipse(xcntr,ycntr,xhlf_wdth,yhlf_wdth,rotation,Xcolumn,Ycolumn) + + "point in a rectangular region" + box(xcntr,ycntr,xfll_wdth,yfll_wdth,rotation,Xcolumn,Ycolumn) + + where + (xcntr,ycntr) are the (x,y) position of the center of the region + (xhlf_wdth,yhlf_wdth) are the (x,y) half widths of the region + (xfll_wdth,yfll_wdth) are the (x,y) full widths of the region + (radius) is half the diameter of the circle + (rotation) is the angle(degrees) that the region is rotated with + respect to (xcntr,ycntr) + (Xcoord,Ycoord) are the (x,y) coordinates to test, usually column + names + NOTE: each parameter can itself be an expression, not merely a + column name or constant. +- + +***5. Example Row Filters +- + [ binary && mag <= 5.0] - Extract all binary stars brighter + than fifth magnitude (note that + the initial space is necessary to + prevent it from being treated as a + binning specification) + + [#row >= 125 && #row <= 175] - Extract row numbers 125 through 175 + + [IMAGE[4,5] .gt. 100] - Extract all rows that have the + (4,5) component of the IMAGE column + greater than 100 + + [abs(sin(theta * #deg)) < 0.5] - Extract all rows having the + absolute value of the sine of theta + less than a half where the angles + are tabulated in degrees + + [SUM( SPEC > 3*BACKGRND )>=1] - Extract all rows containing a + spectrum, held in vector column + SPEC, with at least one value 3 + times greater than the background + level held in a keyword, BACKGRND + + [VCOL=={1,4,2}] - Extract all rows whose vector column + VCOL contains the 3-elements 1, 4, and + 2. + + [@rowFilter.txt] - Extract rows using the expression + contained within the text file + rowFilter.txt + + [gtifilter()] - Search the current file for a GTI + extension, filter the TIME + column in the current table, using + START/STOP times taken from + columns in the GTI extension + + [regfilter("pow.reg")] - Extract rows which have a coordinate + (as given in the X and Y columns) + within the spatial region specified + in the pow.reg region file. + + [regfilter("pow.reg", Xs, Ys)] - Same as above, except that the + Xs and Ys columns will be used to + determine the coordinate of each + row in the table. +- + +**J. Binning or Histogramming Specification + +The optional binning specifier is enclosed in square brackets and can +be distinguished from a general row filter specification by the fact +that it begins with the keyword 'bin' not immediately followed by an +equals sign. When binning is specified, a temporary N-dimensional FITS +primary array is created by computing the histogram of the values in +the specified columns of a FITS table extension. After the histogram +is computed the input FITS file containing the table is then closed and +the temporary FITS primary array is opened and passed to the +application program. Thus, the application program never sees the +original FITS table and only sees the image in the new temporary file +(which has no additional extensions). Obviously, the application +program must be expecting to open a FITS image and not a FITS table in +this case. + +The data type of the FITS histogram image may be specified by appending +'b' (for 8-bit byte), 'i' (for 16-bit integers), 'j' (for 32-bit +integer), 'r' (for 32-bit floating points), or 'd' (for 64-bit double +precision floating point) to the 'bin' keyword (e.g. '[binr X]' +creates a real floating point image). If the data type is not +explicitly specified then a 32-bit integer image will be created by +default, unless the weighting option is also specified in which case +the image will have a 32-bit floating point data type by default. + +The histogram image may have from 1 to 4 dimensions (axes), depending +on the number of columns that are specified. The general form of the +binning specification is: +- + [bin{bijrd} Xcol=min:max:binsize, Ycol= ..., Zcol=..., Tcol=...; weight] +- +in which up to 4 columns, each corresponding to an axis of the image, +are listed. The column names are case insensitive, and the column +number may be given instead of the name, preceded by a pound sign +(e.g., [bin \#4=1:512]). If the column name is not specified, then +CFITSIO will first try to use the 'preferred column' as specified by +the CPREF keyword if it exists (e.g., 'CPREF = 'DETX,DETY'), otherwise +column names 'X', 'Y', 'Z', and 'T' will be assumed for each of the 4 +axes, respectively. In cases where the column name could be confused +with an arithmetic expression, enclose the column name in parentheses to +force the name to be interpreted literally. + +Each column name may be followed by an equals sign and then the lower +and upper range of the histogram, and the size of the histogram bins, +separated by colons. Spaces are allowed before and after the equals +sign but not within the 'min:max:binsize' string. The min, max and +binsize values may be integer or floating point numbers, or they may be +the names of keywords in the header of the table. If the latter, then +the value of that keyword is substituted into the expression. + +Default values for the min, max and binsize quantities will be +used if not explicitly given in the binning expression as shown +in these examples: +- + [bin x = :512:2] - use default minimum value + [bin x = 1::2] - use default maximum value + [bin x = 1:512] - use default bin size + [bin x = 1:] - use default maximum value and bin size + [bin x = :512] - use default minimum value and bin size + [bin x = 2] - use default minimum and maximum values + [bin x] - use default minimum, maximum and bin size + [bin 4] - default 2-D image, bin size = 4 in both axes + [bin] - default 2-D image +- +CFITSIO will use the value of the TLMINn, TLMAXn, and TDBINn keywords, +if they exist, for the default min, max, and binsize, respectively. If +they do not exist then CFITSIO will use the actual minimum and maximum +values in the column for the histogram min and max values. The default +binsize will be set to 1, or (max - min) / 10., whichever is smaller, +so that the histogram will have at least 10 bins along each axis. + +A shortcut notation is allowed if all the columns/axes have the same +binning specification. In this case all the column names may be listed +within parentheses, followed by the (single) binning specification, as +in: +- + [bin (X,Y)=1:512:2] + [bin (X,Y) = 5] +- + +The optional weighting factor is the last item in the binning specifier +and, if present, is separated from the list of columns by a +semi-colon. As the histogram is accumulated, this weight is used to +incremented the value of the appropriated bin in the histogram. If the +weighting factor is not specified, then the default weight = 1 is +assumed. The weighting factor may be a constant integer or floating +point number, or the name of a keyword containing the weighting value. +Or the weighting factor may be the name of a table column in which case +the value in that column, on a row by row basis, will be used. + +In some cases, the column or keyword may give the reciprocal of the +actual weight value that is needed. In this case, precede the weight +keyword or column name by a slash '/' to tell CFITSIO to use the +reciprocal of the value when constructing the histogram. + +For complex or commonly used histograms, one can also place its +description into a text file and import it into the binning +specification using the syntax [bin @filename.txt]. The file's +contents can extend over multiple lines, although it must still +conform to the no-spaces rule for the min:max:binsize syntax and each +axis specification must still be comma-separated. Any lines in the +external text file that begin with 2 slash characters ('//') will be +ignored and may be used to add comments into the file. + + Examples: + +- + [bini detx, dety] - 2-D, 16-bit integer histogram + of DETX and DETY columns, using + default values for the histogram + range and binsize + + [bin (detx, dety)=16; /exposure] - 2-D, 32-bit real histogram of DETX + and DETY columns with a bin size = 16 + in both axes. The histogram values + are divided by the EXPOSURE keyword + value. + + [bin time=TSTART:TSTOP:0.1] - 1-D lightcurve, range determined by + the TSTART and TSTOP keywords, + with 0.1 unit size bins. + + [bin pha, time=8000.:8100.:0.1] - 2-D image using default binning + of the PHA column for the X axis, + and 1000 bins in the range + 8000. to 8100. for the Y axis. + + [bin @binFilter.txt] - Use the contents of the text file + binFilter.txt for the binning + specifications. + +- +*X. Template Files + +When a new FITS file is created with a call to fits\_create\_file, the +name of a template file may be supplied in parentheses immediately +following the name of the new file to be created. This template is +used to define the structure of one or more HDUs in the new file. The +template file may be another FITS file, in which case the newly created +file will have exactly the same keywords in each HDU as in the template +FITS file, but all the data units will be filled with zeros. The +template file may also be an ASCII text file, where each line (in +general) describes one FITS keyword record. The format of the ASCII +template file is described in the following sections. + +**A Detailed Template Line Format + +The format of each ASCII template line closely follows the format of a +FITS keyword record: +- + KEYWORD = KEYVALUE / COMMENT +- +except that free format may be used (e.g., the equals sign may appear +at any position in the line) and TAB characters are allowed and are +treated the same as space characters. The KEYVALUE and COMMENT fields +are optional. The equals sign character is also optional, but it is +recommended that it be included for clarity. Any template line that +begins with the pound '\#' character is ignored by the template parser +and may be use to insert comments into the template file itself. + +The KEYWORD name field is limited to 8 characters in length and only +the letters A-Z, digits 0-9, and the hyphen and underscore characters +may be used, without any embedded spaces. Lowercase letters in the +template keyword name will be converted to uppercase. Leading spaces +in the template line preceding the keyword name are generally ignored, +except if the first 8 characters of a template line are all blank, then +the entire line is treated as a FITS comment keyword (with a blank +keyword name) and is copied verbatim into the FITS header. + +The KEYVALUE field may have any allowed FITS data type: character +string, logical, integer, real, complex integer, or complex real. The +character string values need not be enclosed in single quote characters +unless they are necessary to distinguish the string from a different +data type (e.g. 2.0 is a real but '2.0' is a string). The keyword has +an undefined (null) value if the template record only contains blanks +following the "=" or between the "=" and the "/" comment field +delimiter. + +String keyword values longer than 68 characters (the maximum length +that will fit in a single FITS keyword record) are permitted using the +CFITSIO long string convention. They can either be specified as a +single long line in the template, or by using multiple lines where the +continuing lines contain the 'CONTINUE' keyword, as in this example: +- + LONGKEY = 'This is a long string value that is contin&' + CONTINUE 'ued over 2 records' / comment field goes here +- +The format of template lines with CONTINUE keyword is very strict: 3 +spaces must follow CONTINUE and the rest of the line is copied verbatim +to the FITS file. + +The start of the optional COMMENT field must be preceded by "/", which +is used to separate it from the keyword value field. Exceptions are if +the KEYWORD name field contains COMMENT, HISTORY, CONTINUE, or if the +first 8 characters of the template line are blanks. + +More than one Header-Data Unit (HDU) may be defined in the template +file. The start of an HDU definition is denoted with a SIMPLE or +XTENSION template line: + +1) SIMPLE begins a Primary HDU definition. SIMPLE may only appear as +the first keyword in the template file. If the template file begins +with XTENSION instead of SIMPLE, then a default empty Primary HDU is +created, and the template is then assumed to define the keywords +starting with the first extension following the Primary HDU. + +2) XTENSION marks the beginning of a new extension HDU definition. The +previous HDU will be closed at this point and processing of the next +extension begins. + +**B Auto-indexing of Keywords + +If a template keyword name ends with a "\#" character, it is said to be +'auto-indexed'. Each "\#" character will be replaced by the current +integer index value, which gets reset = 1 at the start of each new HDU +in the file (or 7 in the special case of a GROUP definition). The +FIRST indexed keyword in each template HDU definition is used as the +'incrementor'; each subsequent occurrence of this SAME keyword will +cause the index value to be incremented. This behavior can be rather +subtle, as illustrated in the following examples in which the TTYPE +keyword is the incrementor in both cases: +- + TTYPE# = TIME + TFORM# = 1D + TTYPE# = RATE + TFORM# = 1E +- +will create TTYPE1, TFORM1, TTYPE2, and TFORM2 keywords. But if the +template looks like, +- + TTYPE# = TIME + TTYPE# = RATE + TFORM# = 1D + TFORM# = 1E +- +this results in a FITS files with TTYPE1, TTYPE2, TFORM2, and TFORM2, +which is probably not what was intended! + +**C Template Parser Directives + +In addition to the template lines which define individual keywords, the +template parser recognizes 3 special directives which are each preceded +by the backslash character: \verb+ \include, \group+, and \verb+ \end+. + +The 'include' directive must be followed by a filename. It forces the +parser to temporarily stop reading the current template file and begin +reading the include file. Once the parser reaches the end of the +include file it continues parsing the current template file. Include +files can be nested, and HDU definitions can span multiple template +files. + +The start of a GROUP definition is denoted with the 'group' directive, +and the end of a GROUP definition is denoted with the 'end' directive. +Each GROUP contains 0 or more member blocks (HDUs or GROUPs). Member +blocks of type GROUP can contain their own member blocks. The GROUP +definition itself occupies one FITS file HDU of special type (GROUP +HDU), so if a template specifies 1 group with 1 member HDU like: +- +\group +grpdescr = 'demo' +xtension bintable +# this bintable has 0 cols, 0 rows +\end +- +then the parser creates a FITS file with 3 HDUs : +- +1) dummy PHDU +2) GROUP HDU (has 1 member, which is bintable in HDU number 3) +3) bintable (member of GROUP in HDU number 2) +- +Technically speaking, the GROUP HDU is a BINTABLE with 6 columns. Applications +can define additional columns in a GROUP HDU using TFORMn and TTYPEn +(where n is 7, 8, ....) keywords or their auto-indexing equivalents. + +For a more complicated example of a template file using the group directives, +look at the sample.tpl file that is included in the CFITSIO distribution. + +**D Formal Template Syntax + +The template syntax can formally be defined as follows: +- + TEMPLATE = BLOCK [ BLOCK ... ] + + BLOCK = { HDU | GROUP } + + GROUP = \GROUP [ BLOCK ... ] \END + + HDU = XTENSION [ LINE ... ] { XTENSION | \GROUP | \END | EOF } + + LINE = [ KEYWORD [ = ] ] [ VALUE ] [ / COMMENT ] + + X ... - X can be present 1 or more times + { X | Y } - X or Y + [ X ] - X is optional +- + +At the topmost level, the template defines 1 or more template blocks. Blocks +can be either HDU (Header Data Unit) or a GROUP. For each block the parser +creates 1 (or more for GROUPs) FITS file HDUs. + + +**E Errors + +In general the fits\_execute\_template() function tries to be as atomic +as possible, so either everything is done or nothing is done. If an +error occurs during parsing of the template, fits\_execute\_template() +will (try to) delete the top level BLOCK (with all its children if any) +in which the error occurred, then it will stop reading the template file +and it will return with an error. + +**F Examples + +1. This template file will create a 200 x 300 pixel image, with 4-byte +integer pixel values, in the primary HDU: +- + SIMPLE = T + BITPIX = 32 + NAXIS = 2 / number of dimensions + NAXIS1 = 100 / length of first axis + NAXIS2 = 200 / length of second axis + OBJECT = NGC 253 / name of observed object +- +The allowed values of BITPIX are 8, 16, 32, -32, or -64, +representing, respectively, 8-bit integer, 16-bit integer, 32-bit +integer, 32-bit floating point, or 64 bit floating point pixels. + +2. To create a FITS table, the template first needs to include +XTENSION = TABLE or BINTABLE to define whether it is an ASCII or binary +table, and NAXIS2 to define the number of rows in the table. Two +template lines are then needed to define the name (TTYPEn) and FITS data +format (TFORMn) of the columns, as in this example: +- + xtension = bintable + naxis2 = 40 + ttype# = Name + tform# = 10a + ttype# = Npoints + tform# = j + ttype# = Rate + tunit# = counts/s + tform# = e +- +The above example defines a null primary array followed by a 40-row +binary table extension with 3 columns called 'Name', 'Npoints', and +'Rate', with data formats of '10A' (ASCII character string), '1J' +(integer) and '1E' (floating point), respectively. Note that the other +required FITS keywords (BITPIX, NAXIS, NAXIS1, PCOUNT, GCOUNT, TFIELDS, +and END) do not need to be explicitly defined in the template because +their values can be inferred from the other keywords in the template. +This example also illustrates that the templates are generally +case-insensitive (the keyword names and TFORMn values are converted to +upper-case in the FITS file) and that string keyword values generally +do not need to be enclosed in quotes. + +*XI. Local FITS Conventions + +CFITSIO supports several local FITS conventions which are not +defined in the official NOST FITS standard and which are not +necessarily recognized or supported by other FITS software packages. +Programmers should be cautious about using these features, especially +if the FITS files that are produced are expected to be processed by +other software systems which do not use the CFITSIO interface. + +**A. 64-Bit Long Integers + +CFITSIO supports reading and writing FITS images or table columns containing +64-bit integer data values. Support for 64-bit integers was added to the +official FITS Standard in December 2005. + FITS 64-bit images have BITPIX = +64, and the 64-bit binary table columns have TFORMn = 'K'. CFITSIO also +supports the 'Q' variable-length array table column format which is +analogous to the 'P' column format except that the array descriptor +is stored as a pair of 64-bit integers. + +For the convenience of C programmers, the fitsio.h include file +defines (with a typedef statement) the 'LONGLONG' datatype to be +equivalent to an appropriate 64-bit integer datatype on each platform. +Since there is currently no universal standard +for the name of the 64-bit integer datatype (it might be defined as +'long long', 'long', or '\_\_int64' depending on the platform) +C programmers may prefer to use the 'LONGLONG' datatype when +declaring or allocating 64-bit integer quantities when writing +code which needs to run on multiple platforms. +Note that CFITSIO will implicitly convert the datatype when reading +or writing FITS 64-bit integer images and columns with data arrays of +a different integer or floating point datatype, but there is an +increased risk of loss of numerical precision or +numerical overflow in this case. + +**B. Long String Keyword Values. + +The length of a standard FITS string keyword is limited to 68 +characters because it must fit entirely within a single FITS header +keyword record. In some instances it is necessary to encode strings +longer than this limit, so CFITSIO supports a local convention in which +the string value is continued over multiple keywords. This +continuation convention uses an ampersand character at the end of each +substring to indicate that it is continued on the next keyword, and the +continuation keywords all have the name CONTINUE without an equal sign +in column 9. The string value may be continued in this way over as many +additional CONTINUE keywords as is required. The following lines +illustrate this continuation convention which is used in the value of +the STRKEY keyword: +- +LONGSTRN= 'OGIP 1.0' / The OGIP Long String Convention may be used. +STRKEY = 'This is a very long string keyword&' / Optional Comment +CONTINUE ' value that is continued over 3 keywords in the & ' +CONTINUE 'FITS header.' / This is another optional comment. +- +It is recommended that the LONGSTRN keyword, as shown here, always be +included in any HDU that uses this longstring convention as a warning +to any software that must read the keywords. A routine called fits\_write\_key\_longwarn +has been provided in CFITSIO to write this keyword if it does not +already exist. + +This long string convention is supported by the following CFITSIO +routines: +- + fits_write_key_longstr - write a long string keyword value + fits_insert_key_longstr - insert a long string keyword value + fits_modify_key_longstr - modify a long string keyword value + fits_update_key_longstr - modify a long string keyword value + fits_read_key_longstr - read a long string keyword value + fits_delete_key - delete a keyword +- +The fits\_read\_key\_longstr routine is unique among all the CFITSIO +routines in that it internally allocates memory for the long string +value; all the other CFITSIO routines that deal with arrays require +that the calling program pre-allocate adequate space to hold the array +of data. Consequently, programs which use the fits\_read\_key\_longstr +routine must be careful to free the allocated memory for the string +when it is no longer needed. + +The following 2 routines also have limited support for this long string +convention, +- + fits_modify_key_str - modify an existing string keyword value + fits_update_key_str - update a string keyword value +- +in that they will correctly overwrite an existing long string value, +but the new string value is limited to a maximum of 68 characters in +length. + +The more commonly used CFITSIO routines to write string valued keywords +(fits\_update\_key and fits\_write\_key) do not support this long +string convention and only support strings up to 68 characters in +length. This has been done deliberately to prevent programs from +inadvertently writing keywords using this non-standard convention +without the explicit intent of the programmer or user. The +fits\_write\_key\_longstr routine must be called instead to write long +strings. This routine can also be used to write ordinary string values +less than 68 characters in length. + +**C. Arrays of Fixed-Length Strings in Binary Tables + +CFITSIO supports 2 ways to specify that a character column in a binary +table contains an array of fixed-length strings. The first way, which +is officially supported by the FITS Standard document, uses the TDIMn keyword. +For example, if TFORMn = '60A' and TDIMn = '(12,5)' then that +column will be interpreted as containing an array of 5 strings, each 12 +characters long. + +CFITSIO also supports a +local convention for the format of the TFORMn keyword value of the form +'rAw' where 'r' is an integer specifying the total width in characters +of the column, and 'w' is an integer specifying the (fixed) length of +an individual unit string within the vector. For example, TFORM1 = +'120A10' would indicate that the binary table column is 120 characters +wide and consists of 12 10-character length strings. This convention +is recognized by the CFITSIO routines that read or write strings in +binary tables. The Binary Table definition document specifies that +other optional characters may follow the data type code in the TFORM +keyword, so this local convention is in compliance with the +FITS standard although other FITS readers may not +recognize this convention. + +The Binary Table definition document that was approved by the IAU in +1994 contains an appendix describing an alternate convention for +specifying arrays of fixed or variable length strings in a binary table +character column (with the form 'rA:SSTRw/nnn)'. This appendix was not +officially voted on by the IAU and hence is still provisional. CFITSIO +does not currently support this proposal. + +**D. Keyword Units Strings + +One limitation of the current FITS Standard is that it does not define +a specific convention for recording the physical units of a keyword +value. The TUNITn keyword can be used to specify the physical units of +the values in a table column, but there is no analogous convention for +keyword values. The comment field of the keyword is often used for +this purpose, but the units are usually not specified in a well defined +format that FITS readers can easily recognize and extract. + +To solve this problem, CFITSIO uses a local convention in which the +keyword units are enclosed in square brackets as the first token in the +keyword comment field; more specifically, the opening square bracket +immediately follows the slash '/' comment field delimiter and a single +space character. The following examples illustrate keywords that use +this convention: + +- +EXPOSURE= 1800.0 / [s] elapsed exposure time +V_HELIO = 16.23 / [km s**(-1)] heliocentric velocity +LAMBDA = 5400. / [angstrom] central wavelength +FLUX = 4.9033487787637465E-30 / [J/cm**2/s] average flux +- + +In general, the units named in the IAU(1988) Style Guide are +recommended, with the main exception that the preferred unit for angle +is 'deg' for degrees. + +The fits\_read\_key\_unit and fits\_write\_key\_unit routines in +CFITSIO read and write, respectively, the keyword unit strings in an +existing keyword. + +**E. HIERARCH Convention for Extended Keyword Names + +CFITSIO supports the HIERARCH keyword convention which allows keyword +names that are longer then 8 characters and may contain the full range +of printable ASCII text characters. This convention +was developed at the European Southern Observatory (ESO) to support +hierarchical FITS keyword such as: +- +HIERARCH ESO INS FOCU POS = -0.00002500 / Focus position +- +Basically, this convention uses the FITS keyword 'HIERARCH' to indicate +that this convention is being used, then the actual keyword name +({\tt'ESO INS FOCU POS'} in this example) begins in column 10 and can +contain any printable ASCII text characters, including spaces. The +equals sign marks the end of the keyword name and is followed by the +usual value and comment fields just as in standard FITS keywords. +Further details of this convention are described at +http://arcdev.hq.eso.org/dicb/dicd/dic-1-1.4.html (search for +HIERARCH). + +This convention allows a much broader range of keyword names +than is allowed by the FITS Standard. Here are more examples +of such keywords: +- +HIERARCH LongKeyword = 47.5 / Keyword has > 8 characters, and mixed case +HIERARCH XTE$TEMP = 98.6 / Keyword contains the '$' character +HIERARCH Earth is a star = F / Keyword contains embedded spaces +- +CFITSIO will transparently read and write these keywords, so application +programs do not in general need to know anything about the specific +implementation details of the HIERARCH convention. In particular, +application programs do not need to specify the `HIERARCH' part of the +keyword name when reading or writing keywords (although it +may be included if desired). When writing a keyword, CFITSIO first +checks to see if the keyword name is legal as a standard FITS keyword +(no more than 8 characters long and containing only letters, digits, or +a minus sign or underscore). If so it writes it as a standard FITS +keyword, otherwise it uses the hierarch convention to write the +keyword. The maximum keyword name length is 67 characters, which +leaves only 1 space for the value field. A more practical limit is +about 40 characters, which leaves enough room for most keyword values. +CFITSIO returns an error if there is not enough room for both the +keyword name and the keyword value on the 80-character card, except for +string-valued keywords which are simply truncated so that the closing +quote character falls in column 80. In the current implementation, +CFITSIO preserves the case of the letters when writing the keyword +name, but it is case-insensitive when reading or searching for a +keyword. The current implementation allows any ASCII text character +(ASCII 32 to ASCII 126) in the keyword name except for the '=' +character. A space is also required on either side of the equal sign. + +**F. Tile-Compressed Image Format + +CFITSIO supports a convention for compressing n-dimensional images and +storing the resulting byte stream in a variable-length column in a FITS +binary table. The general principle used in this convention is to +first divide the n-dimensional image into a rectangular grid of +subimages or `tiles'. Each tile is then compressed as a continuous +block of data, and the resulting compressed byte stream is stored in a +row of a variable length column in a FITS binary table. By dividing the +image into tiles it is generally possible to extract and uncompress +subsections of the image without having to uncompress the whole image. +The default tiling pattern treats each row of a 2-dimensional image (or +higher dimensional cube) as a tile, such that each tile contains NAXIS1 +pixels (except the default with the HCOMPRESS algorithm is to +compress the whole 2D image as a single tile). Any other rectangular +tiling pattern may also be defined. In +the case of relatively small images it may be sufficient to compress +the entire image as a single tile, resulting in an output binary table +with 1 row. In the case of 3-dimensional data cubes, it may be +advantageous to treat each plane of the cube as a separate tile if +application software typically needs to access the cube on a plane by +plane basis. + +See section 5.6 ``Image Compression'' +for more information on using this tile-compressed image format. + +*XII. Optimizing Programs + +CFITSIO has been carefully designed to obtain the highest possible +speed when reading and writing FITS files. In order to achieve the +best performance, however, application programmers must be careful to +call the CFITSIO routines appropriately and in an efficient sequence; +inappropriate usage of CFITSIO routines can greatly slow down the +execution speed of a program. + +The maximum possible I/O speed of CFITSIO depends of course on the type +of computer system that it is running on. As a rough guide, the +current generation of workstations can achieve speeds of 2 -- 10 MB/s +when reading or writing FITS images and similar, or slightly slower +speeds with FITS binary tables. Reading of FITS files can occur at +even higher rates (30MB/s or more) if the FITS file is still cached in +system memory following a previous read or write operation on the same +file. To more accurately predict the best performance that is possible +on any particular system, a diagnostic program called ``speed.c'' is +included with the CFITSIO distribution which can be run to +approximately measure the maximum possible speed of writing and reading +a test FITS file. + +The following 2 sections provide some background on how CFITSIO +internally manages the data I/O and describes some strategies that may +be used to optimize the processing speed of software that uses +CFITSIO. + +**A. How CFITSIO Manages Data I/O + +Many CFITSIO operations involve transferring only a small number of +bytes to or from the FITS file (e.g, reading a keyword, or writing a +row in a table); it would be very inefficient to physically read or +write such small blocks of data directly in the FITS file on disk, +therefore CFITSIO maintains a set of internal Input--Output (IO) +buffers in RAM memory that each contain one FITS block (2880 bytes) of +data. Whenever CFITSIO needs to access data in the FITS file, it first +transfers the FITS block containing those bytes into one of the IO +buffers in memory. The next time CFITSIO needs to access bytes in the +same block it can then go to the fast IO buffer rather than using a +much slower system disk access routine. The number of available IO +buffers is determined by the NIOBUF parameter (in fitsio2.h) and is +currently set to 40 by default. + +Whenever CFITSIO reads or writes data it first checks to see if that +block of the FITS file is already loaded into one of the IO buffers. +If not, and if there is an empty IO buffer available, then it will load +that block into the IO buffer (when reading a FITS file) or will +initialize a new block (when writing to a FITS file). If all the IO +buffers are already full, it must decide which one to reuse (generally +the one that has been accessed least recently), and flush the contents +back to disk if it has been modified before loading the new block. + +The one major exception to the above process occurs whenever a large +contiguous set of bytes are accessed, as might occur when reading or +writing a FITS image. In this case CFITSIO bypasses the internal IO +buffers and simply reads or writes the desired bytes directly in the +disk file with a single call to a low-level file read or write +routine. The minimum threshold for the number of bytes to read or +write this way is set by the MINDIRECT parameter and is currently set +to 3 FITS blocks = 8640 bytes. This is the most efficient way to read +or write large chunks of data and can achieve IO transfer rates of +5 -- 10MB/s or greater. Note that this fast direct IO process is not +applicable when accessing columns of data in a FITS table because the +bytes are generally not contiguous since they are interleaved by the +other columns of data in the table. This explains why the speed for +accessing FITS tables is generally slower than accessing +FITS images. + +Given this background information, the general strategy for efficiently +accessing FITS files should be apparent: when dealing with FITS +images, read or write large chunks of data at a time so that the direct +IO mechanism will be invoked; when accessing FITS headers or FITS +tables, on the other hand, once a particular FITS block has been +loading into one of the IO buffers, try to access all the needed +information in that block before it gets flushed out of the IO buffer. +It is important to avoid the situation where the same FITS block is +being read then flushed from a IO buffer multiple times. + +The following section gives more specific suggestions for optimizing +the use of CFITSIO. + +**B. Optimization Strategies + +1. Because the data in FITS files is always stored in "big-endian" byte order, +where the first byte of numeric values contains the most significant bits and the +last byte contains the least significant bits, CFITSIO must swap the order of the bytes +when reading or writing FITS files when running on little-endian machines (e.g., +Linux and Microsoft Windows operating systems running on PCs with x86 CPUs). + +On fairly new CPUs that support "SSSE3" machine instructions +(e.g., starting with Intel Core 2 CPUs in 2007, and in AMD CPUs +beginning in 2011) significantly faster 4-byte and 8-byte swapping +algorithms are available. These faster byte swapping functions are +not used by default in CFITSIO (because of the potential code +portablility issues), but users can enable them on supported +platforms by adding the appropriate compiler flags (-mssse3 with gcc +or icc on linux) when compiling the swapproc.c source file, which will +allow the compiler to generate code using the SSSE3 instruction set. +A convenient way to do this is to configure the CFITSIO library +with the following command: +- + > ./configure --enable-ssse3 +- +Note, however, that a binary executable file that is +created using these faster functions will only run on +machines that support the SSSE3 machine instructions. It will +crash on machines that do not support them. + +For faster 2-byte swaps on virtually all x86-64 CPUs (even those that +do not support SSSE3), a variant using only SSE2 instructions exists. +SSE2 is enabled by default on x86\_64 CPUs with 64-bit operating systems +(and is also automatically enabled by the --enable-ssse3 flag). +When running on x86\_64 CPUs with 32-bit operating systems, these faster +2-byte swapping algorithms are not used by default in CFITSIO, but can be +enabled explicitly with: +- +./configure --enable-sse2 +- +Preliminary testing indicates that these SSSE3 and SSE2 based +byte-swapping algorithms can boost the CFITSIO performance when +reading or writing FITS images by 20\% - 30\% or more. +It is important to note, however, that compiler optimization must be +turned on (e.g., by using the -O1 or -O2 flags in gcc) when building +programs that use these fast byte-swapping algorithms in order +to reap the full benefit of the SSSE3 and SSE2 instructions; without +optimization, the code may actually run slower than when using +more traditional byte-swapping techniques. + +2. When dealing with a FITS primary array or IMAGE extension, it is +more efficient to read or write large chunks of the image at a time +(at least 3 FITS blocks = 8640 bytes) so that the direct IO mechanism +will be used as described in the previous section. Smaller chunks of +data are read or written via the IO buffers, which is somewhat less +efficient because of the extra copy operation and additional +bookkeeping steps that are required. In principle it is more efficient +to read or write as big an array of image pixels at one time as +possible, however, if the array becomes so large that the operating +system cannot store it all in RAM, then the performance may be degraded +because of the increased swapping of virtual memory to disk. + +3. When dealing with FITS tables, the most important efficiency factor +in the software design is to read or write the data in the FITS file in +a single pass through the file. An example of poor program design +would be to read a large, 3-column table by sequentially reading the +entire first column, then going back to read the 2nd column, and +finally the 3rd column; this obviously requires 3 passes through the +file which could triple the execution time of an IO limited program. +For small tables this is not important, but when reading multi-megabyte +sized tables these inefficiencies can become significant. The more +efficient procedure in this case is to read or write only as many rows +of the table as will fit into the available internal IO buffers, then +access all the necessary columns of data within that range of rows. +Then after the program is completely finished with the data in those +rows it can move on to the next range of rows that will fit in the +buffers, continuing in this way until the entire file has been +processed. By using this procedure of accessing all the columns of a +table in parallel rather than sequentially, each block of the FITS file +will only be read or written once. + +The optimal number of rows to read or write at one time in a given +table depends on the width of the table row and on the number of IO +buffers that have been allocated in CFITSIO. The CFITSIO Iterator routine +will automatically use the optimal-sized buffer, but there is also a +CFITSIO routine that will return the optimal number of rows for a given +table: fits\_get\_rowsize. It is not critical to use exactly the +value of nrows returned by this routine, as long as one does not exceed +it. Using a very small value however can also lead to poor performance +because of the overhead from the larger number of subroutine calls. + +The optimal number of rows returned by fits\_get\_rowsize is valid only +as long as the application program is only reading or writing data in +the specified table. Any other calls to access data in the table +header would cause additional blocks of data +to be loaded into the IO buffers displacing data from the original +table, and should be avoided during the critical period while the table +is being read or written. + +4. Use the CFITSIO Iterator routine. This routine provides a +more `object oriented' way of reading and writing FITS files +which automatically uses the most appropriate data buffer size +to achieve the maximum I/O throughput. + +5. Use binary table extensions rather than ASCII table +extensions for better efficiency when dealing with tabular data. The +I/O to ASCII tables is slower because of the overhead in formatting or +parsing the ASCII data fields and because ASCII tables are about twice +as large as binary tables that have the same information content. + +6. Design software so that it reads the FITS header keywords in the +same order in which they occur in the file. When reading keywords, +CFITSIO searches forward starting from the position of the last keyword +that was read. If it reaches the end of the header without finding the +keyword, it then goes back to the start of the header and continues the +search down to the position where it started. In practice, as long as +the entire FITS header can fit at one time in the available internal IO +buffers, then the header keyword access will be relatively fast and it makes +little difference which order they are accessed. + +7. Avoid the use of scaling (by using the BSCALE and BZERO or TSCAL and +TZERO keywords) in FITS files since the scaling operations add to the +processing time needed to read or write the data. In some cases it may +be more efficient to temporarily turn off the scaling (using fits\_set\_bscale or +fits\_set\_tscale) and then read or write the raw unscaled values in the FITS +file. + +8. Avoid using the `implicit data type conversion' capability in +CFITSIO. For instance, when reading a FITS image with BITPIX = -32 +(32-bit floating point pixels), read the data into a single precision +floating point data array in the program. Forcing CFITSIO to convert +the data to a different data type can slow the program. + +9. Where feasible, design FITS binary tables using vector column +elements so that the data are written as a contiguous set of bytes, +rather than as single elements in multiple rows. For example, it is +faster to access the data in a table that contains a single row +and 2 columns with TFORM keywords equal to '10000E' and '10000J', than +it is to access the same amount of data in a table with 10000 rows +which has columns with the TFORM keywords equal to '1E' and '1J'. In +the former case the 10000 floating point values in the first column are +all written in a contiguous block of the file which can be read or +written quickly, whereas in the second case each floating point value +in the first column is interleaved with the integer value in the second +column of the same row so CFITSIO has to explicitly move to the +position of each element to be read or written. + +10. Avoid the use of variable length vector columns in binary tables, +since any reading or writing of these data requires that CFITSIO first +look up or compute the starting address of each row of data in the +heap. In practice, this is probably not a significant efficiency issue. + +11. When copying data from one FITS table to another, it is faster to +transfer the raw bytes instead of reading then writing each column of +the table. The CFITSIO routines fits\_read\_tblbytes and +fits\_write\_tblbytes will perform low-level reads or writes of any +contiguous range of bytes in a table extension. These routines can be +used to read or write a whole row (or multiple rows for even greater +efficiency) of a table with a single function call. These routines +are fast because they bypass all the usual data scaling, error checking +and machine dependent data conversion that is normally done by CFITSIO, +and they allow the program to write the data to the output file in +exactly the same byte order. For these same reasons, these routines +can corrupt the FITS data file if used incorrectly because no +validation or machine dependent conversion is performed by these +routines. These routines are only recommended for optimizing critical +pieces of code and should only be used by programmers who thoroughly +understand the internal format of the FITS tables they are reading or +writing. + +12. Another strategy for improving the speed of writing a FITS table, +similar to the previous one, is to directly construct the entire byte +stream for a whole table row (or multiple rows) within the application +program and then write it to the FITS file with +fits\_write\_tblbytes. This avoids all the overhead normally present +in the column-oriented CFITSIO write routines. This technique should +only be used for critical applications because it makes the code more +difficult to understand and maintain, and it makes the code more system +dependent (e.g., do the bytes need to be swapped before writing to the +FITS file?). + +13. Finally, external factors such as the speed of the data storage device, +the size of the data cache, the amount of disk fragmentation, and the amount of +RAM available on the system can all have a significant impact on +overall I/O efficiency. For critical applications, the entire hardware +and software system should be reviewed to identify any +potential I/O bottlenecks. + + +\appendix +*1 Index of Routines +\begin{tabular}{lr} +fits\_add\_group\_member & \pageref{ffgtam} \\ +fits\_ascii\_tform & \pageref{ffasfm} \\ +fits\_binary\_tform & \pageref{ffbnfm} \\ +fits\_calculator & \pageref{ffcalc} \\ +fits\_calculator\_rng & \pageref{ffcalcrng} \\ +fits\_calc\_binning & \pageref{calcbinning} \\ +fits\_calc\_rows & \pageref{ffcrow} \\ +fits\_change\_group & \pageref{ffgtch} \\ +fits\_clear\_errmark & \pageref{ffpmrk} \\ +fits\_clear\_errmsg & \pageref{ffcmsg} \\ +fits\_close\_file & \pageref{ffclos} \\ +fits\_compact\_group & \pageref{ffgtcm} \\ +fits\_compare\_str & \pageref{ffcmps} \\ +fits\_compress\_heap & \pageref{ffcmph} \\ +fits\_convert\_hdr2str & \pageref{ffhdr2str}, \pageref{hdr2str} \\ +fits\_copy\_cell2image & \pageref{copycell} \\ +fits\_copy\_col & \pageref{ffcpcl} \\ +fits\_copy\_data & \pageref{ffcpdt} \\ +fits\_copy\_file & \pageref{ffcpfl} \\ +fits\_copy\_group & \pageref{ffgtcp} \\ +fits\_copy\_hdu & \pageref{ffcopy} \\ +fits\_copy\_header & \pageref{ffcphd} \\ +fits\_copy\_image2cell & \pageref{copycell} \\ +fits\_copy\_image\_section & \pageref{ffcpimg} \\ +fits\_copy\_key & \pageref{ffcpky} \\ +fits\_copy\_member & \pageref{ffgmcp} \\ +fits\_copy\_pixlist2image & \pageref{copypixlist2image} \\ +fits\_copy\_rows & \pageref{ffcprw} \\ +fits\_create\_diskfile & \pageref{ffinit} \\ +fits\_create\_file & \pageref{ffinit} \\ +fits\_create\_group & \pageref{ffgtcr} \\ +fits\_create\_hdu & \pageref{ffcrhd} \\ + +\end{tabular} +\begin{tabular}{lr} +fits\_create\_img & \pageref{ffcrim} \\ +fits\_create\_memfile & \pageref{ffimem} \\ +fits\_create\_tbl & \pageref{ffcrtb} \\ +fits\_create\_template & \pageref{fftplt} \\ +fits\_date2str & \pageref{ffdt2s} \\ +fits\_decode\_chksum & \pageref{ffdsum} \\ +fits\_decode\_tdim & \pageref{ffdtdm} \\ +fits\_delete\_col & \pageref{ffdcol} \\ +fits\_delete\_file & \pageref{ffdelt} \\ +fits\_delete\_hdu & \pageref{ffdhdu} \\ +fits\_delete\_key & \pageref{ffdkey} \\ +fits\_delete\_record & \pageref{ffdrec} \\ +fits\_delete\_rowlist & \pageref{ffdrws} \\ +fits\_delete\_rowrange & \pageref{ffdrrg} \\ +fits\_delete\_rows & \pageref{ffdrow} \\ +fits\_delete\_str & \pageref{ffdkey} \\ +fits\_encode\_chksum & \pageref{ffesum} \\ +fits\_file\_exists & \pageref{ffexist} \\ +fits\_file\_mode & \pageref{ffflmd} \\ +fits\_file\_name & \pageref{ffflnm} \\ +fits\_find\_first\_row & \pageref{ffffrw} \\ +fits\_find\_nextkey & \pageref{ffgnxk} \\ +fits\_find\_rows & \pageref{fffrow} \\ +fits\_flush\_buffer & \pageref{ffflus} \\ +fits\_flush\_file & \pageref{ffflus} \\ +fits\_free\_memory & \pageref{ffgkls} \\ +fits\_get\_acolparms & \pageref{ffgacl} \\ +fits\_get\_bcolparms & \pageref{ffgbcl} \\ +fits\_get\_chksum & \pageref{ffgcks} \\ +fits\_get\_col\_display\_width & \pageref{ffgcdw} \\ +fits\_get\_colname & \pageref{ffgcnn} \\ +fits\_get\_colnum & \pageref{ffgcno} \\ +\end{tabular} +\begin{tabular}{lr} +fits\_get\_coltype & \pageref{ffgtcl} \\ +fits\_get\_compression\_type & \pageref{ffgetcomp} \\ +fits\_get\_eqcoltype & \pageref{ffgtcl} \\ +fits\_get\_errstatus & \pageref{ffgerr} \\ +fits\_get\_hdrpos & \pageref{ffghps} \\ +fits\_get\_hdrspace & \pageref{ffghsp} \\ +fits\_get\_hdu\_num & \pageref{ffghdn} \\ +fits\_get\_hdu\_type & \pageref{ffghdt} \\ +fits\_get\_hduaddr & \pageref{ffghad} \\ +fits\_get\_hduaddrll & \pageref{ffghad} \\ +fits\_get\_img\_dim & \pageref{ffgidm} \\ +fits\_get\_img\_equivtype & \pageref{ffgidt} \\ +fits\_get\_img\_param & \pageref{ffgipr} \\ +fits\_get\_img\_size & \pageref{ffgisz} \\ +fits\_get\_img\_type & \pageref{ffgidt} \\ +fits\_get\_inttype & \pageref{ffinttyp} \\ +fits\_get\_keyclass & \pageref{ffgkcl} \\ +fits\_get\_keyname & \pageref{ffgknm} \\ +fits\_get\_keytype & \pageref{ffdtyp} \\ +fits\_get\_noise\_bits & \pageref{ffgetcomp} \\ +fits\_get\_num\_cols & \pageref{ffgnrw} \\ +fits\_get\_num\_groups & \pageref{ffgmng} \\ +fits\_get\_num\_hdus & \pageref{ffthdu} \\ +fits\_get\_num\_members & \pageref{ffgtnm} \\ +fits\_get\_num\_rows & \pageref{ffgnrw} \\ +fits\_get\_rowsize & \pageref{ffgrsz} \\ +fits\_get\_system\_time & \pageref{ffdt2s} \\ +fits\_get\_tile\_dim & \pageref{ffgetcomp} \\ +fits\_get\_tbcol & \pageref{ffgabc} \\ +fits\_get\_version & \pageref{ffvers} \\ +fits\_hdr2str & \pageref{ffhdr2str}, \pageref{hdr2str} \\ +fits\_insert\_atbl & \pageref{ffitab} \\ +\end{tabular} +\newpage +\begin{tabular}{lr} +fits\_insert\_btbl & \pageref{ffibin} \\ +fits\_insert\_col & \pageref{fficol} \\ +fits\_insert\_cols & \pageref{fficls} \\ +fits\_insert\_group & \pageref{ffgtis} \\ +fits\_insert\_img & \pageref{ffiimg} \\ +fits\_insert\_key\_null & \pageref{ffikyu} \\ +fits\_insert\_key\_TYP & \pageref{ffikyx} \\ +fits\_insert\_record & \pageref{ffirec} \\ +fits\_insert\_rows & \pageref{ffirow} \\ +fits\_is\_reentrant & \pageref{reentrant} \\ +fits\_iterate\_data & \pageref{ffiter} \\ +fits\_make\_hist & \pageref{makehist} \\ +fits\_make\_keyn & \pageref{ffkeyn} \\ +fits\_make\_nkey & \pageref{ffnkey} \\ +fits\_merge\_groups & \pageref{ffgtmg} \\ +fits\_modify\_card & \pageref{ffmcrd} \\ +fits\_modify\_comment & \pageref{ffmcom} \\ +fits\_modify\_key\_null & \pageref{ffmkyu} \\ +fits\_modify\_key\_TYP & \pageref{ffmkyx} \\ +fits\_modify\_name & \pageref{ffmnam} \\ +fits\_modify\_record & \pageref{ffmrec} \\ +fits\_modify\_vector\_len & \pageref{ffmvec} \\ +fits\_movabs\_hdu & \pageref{ffmahd} \\ +fits\_movnam\_hdu & \pageref{ffmnhd} \\ +fits\_movrel\_hdu & \pageref{ffmrhd} \\ +fits\_null\_check & \pageref{ffnchk} \\ +fits\_open\_data & \pageref{ffopen} \\ +fits\_open\_diskfile & \pageref{ffopen} \\ +fits\_open\_file & \pageref{ffopen} \\ +fits\_open\_image & \pageref{ffopen} \\ +fits\_open\_table & \pageref{ffopen} \\ +fits\_open\_group & \pageref{ffgtop} \\ +fits\_open\_member & \pageref{ffgmop} \\ +fits\_open\_memfile & \pageref{ffomem} \\ +fits\_parse\_extnum & \pageref{ffextn} \\ +fits\_parse\_input\_filename & \pageref{ffiurl} \\ +fits\_parse\_input\_url & \pageref{ffiurl} \\ +fits\_parse\_range & \pageref{ffrwrg} \\ +fits\_parse\_rootname & \pageref{ffrtnm} \\ +fits\_parse\_template & \pageref{ffgthd} \\ +fits\_parse\_value & \pageref{ffpsvc} \\ +fits\_pix\_to\_world & \pageref{ffwldp} \\ +fits\_read\_2d\_TYP & \pageref{ffg2dx} \\ +fits\_read\_3d\_TYP & \pageref{ffg3dx} \\ +fits\_read\_atblhdr & \pageref{ffghtb} \\ +fits\_read\_btblhdr & \pageref{ffghbn} \\ +fits\_read\_card & \pageref{ffgcrd} \\ +fits\_read\_col & \pageref{ffgcv} \\ +\end{tabular} +\begin{tabular}{lr} +fits\_read\_col\_bit\_ & \pageref{ffgcx} \\ +fits\_read\_col\_TYP & \pageref{ffgcvx} \\ +fits\_read\_colnull & \pageref{ffgcf} \\ +fits\_read\_colnull\_TYP & \pageref{ffgcfx} \\ +fits\_read\_descript & \pageref{ffgdes} \\ +fits\_read\_descripts & \pageref{ffgdes} \\ +fits\_read\_errmsg & \pageref{ffgmsg} \\ +fits\_read\_ext & \pageref{ffgextn} \\ +fits\_read\_grppar\_TYP & \pageref{ffggpx} \\ +fits\_read\_img & \pageref{ffgpv} \\ +fits\_read\_img\_coord & \pageref{ffgics} \\ +fits\_read\_img\_TYP & \pageref{ffgpvx} \\ +fits\_read\_imghdr & \pageref{ffghpr} \\ +fits\_read\_imgnull & \pageref{ffgpf} \\ +fits\_read\_imgnull\_TYP & \pageref{ffgpfx} \\ +fits\_read\_key & \pageref{ffgky} \\ +fits\_read\_key\_longstr & \pageref{ffgkls} \\ +fits\_read\_key\_triple & \pageref{ffgkyt} \\ +fits\_read\_key\_unit & \pageref{ffgunt} \\ +fits\_read\_key\_TYP & \pageref{ffgkyx} \\ +fits\_read\_keyn & \pageref{ffgkyn} \\ +fits\_read\_keys\_TYP & \pageref{ffgknx} \\ +fits\_read\_keyword & \pageref{ffgkey} \\ +fits\_read\_pix & \pageref{ffgpxv} \\ +fits\_read\_pixnull & \pageref{ffgpxf} \\ +fits\_read\_record & \pageref{ffgrec} \\ +fits\_read\_str & \pageref{ffgcrd} \\ +fits\_read\_subset\_TYP & \pageref{ffgsvx} \pageref{ffgsvx2}\\ +fits\_read\_subsetnull\_TYP & \pageref{ffgsfx} \pageref{ffgsfx2} \\ +fits\_read\_tbl\_coord & \pageref{ffgtcs} \\ +fits\_read\_tblbytes & \pageref{ffgtbb} \\ +fits\_read\_tdim & \pageref{ffgtdm} \\ +fits\_read\_wcstab & \pageref{wcstab} \\ +fits\_rebin\_wcs & \pageref{rebinwcs} \\ +fits\_remove\_group & \pageref{ffgtrm} \\ +fits\_remove\_member & \pageref{ffgmrm} \\ +fits\_reopen\_file & \pageref{ffreopen} \\ +fits\_report\_error & \pageref{ffrprt} \\ +fits\_resize\_img & \pageref{ffrsim} \\ +fits\_rms\_float & \pageref{imageRMS} \\ +fits\_rms\_short & \pageref{imageRMS} \\ +fits\_select\_rows & \pageref{ffsrow} \\ +fits\_set\_atblnull & \pageref{ffsnul} \\ +fits\_set\_bscale & \pageref{ffpscl} \\ +fits\_set\_btblnull & \pageref{fftnul} \\ +fits\_set\_compression\_type & \pageref{ffsetcomp} \\ +fits\_set\_hdrsize & \pageref{ffhdef} \\ +fits\_set\_hdustruc & \pageref{ffrdef} \\ +\end{tabular} +\begin{tabular}{lr} +fits\_set\_imgnull & \pageref{ffpnul} \\ +fits\_set\_noise\_bits & \pageref{ffsetcomp} \\ +fits\_set\_tile\_dim & \pageref{ffsetcomp} \\ +fits\_set\_tscale & \pageref{fftscl} \\ +fits\_split\_names & \pageref{splitnames} \\ +fits\_str2date & \pageref{ffdt2s} \\ +fits\_str2time & \pageref{ffdt2s} \\ +fits\_test\_expr & \pageref{fftexp} \\ +fits\_test\_heap & \pageref{fftheap} \\ +fits\_test\_keyword & \pageref{fftkey} \\ +fits\_test\_record & \pageref{fftrec} \\ +fits\_time2str & \pageref{ffdt2s} \\ +fits\_transfer\_member & \pageref{ffgmtf} \\ +fits\_translate\_keyword & \pageref{translatekey} \\ +fits\_update\_card & \pageref{ffucrd} \\ +fits\_update\_chksum & \pageref{ffupck} \\ +fits\_update\_key & \pageref{ffuky} \\ +fits\_update\_key\_longstr & \pageref{ffukyx} \\ +fits\_update\_key\_null & \pageref{ffukyu} \\ +fits\_update\_key\_TYP & \pageref{ffukyx} \\ +fits\_uppercase & \pageref{ffupch} \\ +fits\_url\_type & \pageref{ffurlt} \\ +fits\_verify\_chksum & \pageref{ffvcks} \\ +fits\_verify\_group & \pageref{ffgtvf} \\ +fits\_world\_to\_pix & \pageref{ffxypx} \\ +fits\_write\_2d\_TYP & \pageref{ffp2dx} \\ +fits\_write\_3d\_TYP & \pageref{ffp3dx} \\ +fits\_write\_atblhdr & \pageref{ffphtb} \\ +fits\_write\_btblhdr & \pageref{ffphbn} \\ +fits\_write\_chksum & \pageref{ffpcks} \\ +fits\_write\_col & \pageref{ffpcl} \\ +fits\_write\_col\_bit & \pageref{ffpclx} \\ +fits\_write\_col\_TYP & \pageref{ffpcls} \\ +fits\_write\_col\_null & \pageref{ffpclu} \\ +fits\_write\_colnull & \pageref{ffpcn} \\ +fits\_write\_colnull\_TYP & \pageref{ffpcnx} \\ +fits\_write\_comment & \pageref{ffpcom} \\ +fits\_write\_date & \pageref{ffpdat} \\ +fits\_write\_descript & \pageref{ffpdes} \\ +fits\_write\_errmark & \pageref{ffpmrk} \\ +fits\_write\_errmsg & \pageref{ffpmsg} \\ +fits\_write\_ext & \pageref{ffgextn} \\ +fits\_write\_exthdr & \pageref{ffphps} \\ +fits\_write\_grphdr & \pageref{ffphpr} \\ +fits\_write\_grppar\_TYP & \pageref{ffpgpx} \\ +fits\_write\_hdu & \pageref{ffwrhdu} \\ +fits\_write\_history & \pageref{ffphis} \\ +fits\_write\_img & \pageref{ffppr} \\ +\end{tabular} +\newpage +\begin{tabular}{lr} +fits\_write\_img\_null & \pageref{ffppru} \\ +fits\_write\_img\_TYP & \pageref{ffpprx} \\ +fits\_write\_imghdr & \pageref{ffphps} \\ +fits\_write\_imgnull & \pageref{ffppn} \\ +fits\_write\_imgnull\_TYP & \pageref{ffppnx} \\ +fits\_write\_key & \pageref{ffpky} \\ +fits\_write\_key\_longstr & \pageref{ffpkls} \\ +fits\_write\_key\_longwarn & \pageref{ffplsw} \\ +fits\_write\_key\_null & \pageref{ffpkyu} \\ +fits\_write\_key\_template & \pageref{ffpktp} \\ +fits\_write\_key\_triple & \pageref{ffpkyt} \\ +fits\_write\_key\_unit & \pageref{ffpunt} \\ +fits\_write\_key\_TYP & \pageref{ffpkyx} \\ +fits\_write\_keys\_TYP & \pageref{ffpknx} \\ +fits\_write\_keys\_histo & \pageref{writekeyshisto} \\ +fits\_write\_null\_img & \pageref{ffpprn} \\ +fits\_write\_nullrows & \pageref{ffpclu} \\ +fits\_write\_pix & \pageref{ffppx} \\ +fits\_write\_pixnull & \pageref{ffppxn} \\ +fits\_write\_record & \pageref{ffprec} \\ +fits\_write\_subset & \pageref{ffpss} \\ +fits\_write\_subset\_TYP & \pageref{ffpssx} \\ +fits\_write\_tblbytes & \pageref{ffptbb} \\ +fits\_write\_tdim & \pageref{ffptdm} \\ +fits\_write\_theap & \pageref{ffpthp} \\ +\end{tabular} +\newpage +\begin{tabular}{lr} +ffasfm & \pageref{ffasfm} \\ +ffbnfm & \pageref{ffbnfm} \\ +ffcalc & \pageref{ffcalc} \\ +ffcalc\_rng & \pageref{ffcalcrng} \\ +ffclos & \pageref{ffclos} \\ +ffcmph & \pageref{ffcmph} \\ +ffcmps & \pageref{ffcmps} \\ +ffcmrk & \pageref{ffpmrk} \\ +ffcmsg & \pageref{ffcmsg} \\ +ffcopy & \pageref{ffcopy} \\ +ffcpcl & \pageref{ffcpcl} \\ +ffcpdt & \pageref{ffcpdt} \\ +ffcpfl & \pageref{ffcpfl} \\ +ffcphd & \pageref{ffcphd} \\ +ffcpimg & \pageref{ffcpimg} \\ +ffcpky & \pageref{ffcpky} \\ +ffcprw & \pageref{ffcprw} \\ +ffcrhd & \pageref{ffcrhd} \\ +ffcrim & \pageref{ffcrim} \\ +ffcrow & \pageref{ffcrow} \\ +ffcrtb & \pageref{ffcrtb} \\ +ffdcol & \pageref{ffdcol} \\ +ffdelt & \pageref{ffdelt} \\ +ffdhdu & \pageref{ffdhdu} \\ +ffdkey & \pageref{ffdkey} \\ +ffdkinit & \pageref{ffinit} \\ +ffdkopen & \pageref{ffopen} \\ +ffdopn & \pageref{ffopen} \\ +ffdrec & \pageref{ffdrec} \\ +ffdrow & \pageref{ffdrow} \\ +ffdrrg & \pageref{ffdrrg} \\ +ffdrws & \pageref{ffdrws} \\ +ffdstr & \pageref{ffdkey} \\ +ffdsum & \pageref{ffdsum} \\ +ffdt2s & \pageref{ffdt2s} \\ +ffdtdm & \pageref{ffdtdm} \\ +ffdtyp & \pageref{ffdtyp} \\ +ffeqty & \pageref{ffgtcl} \\ +ffesum & \pageref{ffesum} \\ +ffexest & \pageref{ffexist} \\ +ffextn & \pageref{ffextn} \\ +ffffrw & \pageref{ffffrw} \\ +ffflmd & \pageref{ffflmd} \\ +ffflnm & \pageref{ffflnm} \\ +ffflsh & \pageref{ffflus} \\ +ffflus & \pageref{ffflus} \\ +fffree & \pageref{ffgkls} \\ +fffrow & \pageref{fffrow} \\ +\end{tabular} +\begin{tabular}{lr} +ffg2d\_ & \pageref{ffg2dx} \\ +ffg3d\_ & \pageref{ffg3dx} \\ +ffgabc & \pageref{ffgabc} \\ +ffgacl & \pageref{ffgacl} \\ +ffgbcl & \pageref{ffgbcl} \\ +ffgcdw & \pageref{ffgcdw} \\ +ffgcf & \pageref{ffgcf} \\ +ffgcf\_ & \pageref{ffgcfx} \\ +ffgcks & \pageref{ffgcks} \\ +ffgcnn & \pageref{ffgcnn} \\ +ffgcno & \pageref{ffgcno} \\ +ffgcrd & \pageref{ffgcrd} \\ +ffgcv & \pageref{ffgcv} \\ +ffgcv\_ & \pageref{ffgcvx} \\ +ffgcx & \pageref{ffgcx} \\ +ffgdes & \pageref{ffgdes} \\ +ffgdess & \pageref{ffgdes} \\ +ffgerr & \pageref{ffgerr} \\ +ffgextn & \pageref{ffgextn} \\ +ffggp\_ & \pageref{ffggpx} \\ +ffghad & \pageref{ffghad} \\ +ffghbn & \pageref{ffghbn} \\ +ffghdn & \pageref{ffghdn} \\ +ffghdt & \pageref{ffghdt} \\ +ffghpr & \pageref{ffghpr} \\ +ffghps & \pageref{ffghps} \\ +ffghsp & \pageref{ffghsp} \\ +ffghtb & \pageref{ffghtb} \\ +ffgics & \pageref{ffgics} \\ +ffgidm & \pageref{ffgidm} \\ +ffgidt & \pageref{ffgidt} \\ +ffgiet & \pageref{ffgidt} \\ +ffgipr & \pageref{ffgipr} \\ +ffgisz & \pageref{ffgisz} \\ +ffgkcl & \pageref{ffgkcl} \\ +ffgkey & \pageref{ffgkey} \\ +ffgkls & \pageref{ffgkls} \\ +ffgkn\_ & \pageref{ffgknx} \\ +ffgknm & \pageref{ffgknm} \\ +ffgky & \pageref{ffgky} \\ +ffgkyn & \pageref{ffgkyn} \\ +ffgkyt & \pageref{ffgkyt} \\ +ffgky\_ & \pageref{ffgkyx} \\ +ffgmcp & \pageref{ffgmcp} \\ +ffgmng & \pageref{ffgmng} \\ +ffgmop & \pageref{ffgmop} \\ +ffgmrm & \pageref{ffgmrm} \\ +ffgmsg & \pageref{ffgmsg} \\ + +\end{tabular} +\begin{tabular}{lr} +ffgmtf & \pageref{ffgmtf} \\ +ffgncl & \pageref{ffgnrw} \\ +ffgnrw & \pageref{ffgnrw} \\ +ffgnxk & \pageref{ffgnxk} \\ +ffgpf & \pageref{ffgpf} \\ +ffgpf\_ & \pageref{ffgpfx} \\ +ffgpv & \pageref{ffgpv} \\ +ffgpv\_ & \pageref{ffgpvx} \\ +ffgpxv & \pageref{ffgpxv} \\ +ffgpxf & \pageref{ffgpxf} \\ +ffgrec & \pageref{ffgrec} \\ +ffgrsz & \pageref{ffgrsz} \\ +ffgsdt & \pageref{ffdt2s} \\ +ffgsf\_ & \pageref{ffgsfx} \pageref{ffgsfx2} \\ +ffgstm & \pageref{ffdt2s} \\ +ffgstr & \pageref{ffgcrd} \\ +ffgsv\_ & \pageref{ffgsvx} \pageref{ffgsvx2}\\ +ffgtam & \pageref{ffgtam} \\ +ffgtbb & \pageref{ffgtbb} \\ +ffgtch & \pageref{ffgtch} \\ +ffgtcl & \pageref{ffgtcl} \\ +ffgtcm & \pageref{ffgtcm} \\ +ffgtcp & \pageref{ffgtcp} \\ +ffgtcr & \pageref{ffgtcr} \\ +ffgtcs & \pageref{ffgtcs} \\ +ffgtdm & \pageref{ffgtdm} \\ +ffgthd & \pageref{ffgthd} \\ +ffgtis & \pageref{ffgtis} \\ +ffgtmg & \pageref{ffgtmg} \\ +ffgtnm & \pageref{ffgtnm} \\ +ffgtop & \pageref{ffgtop} \\ +ffgtrm & \pageref{ffgtrm} \\ +ffgtvf & \pageref{ffgtvf} \\ +ffgunt & \pageref{ffgunt} \\ +ffhdef & \pageref{ffhdef} \\ +ffibin & \pageref{ffibin} \\ +fficls & \pageref{fficls} \\ +fficol & \pageref{fficol} \\ +ffifile & \pageref{ffiurl} \\ +ffiimg & \pageref{ffiimg} \\ +ffikls & \pageref{ffikyx} \\ +ffikyu & \pageref{ffikyu} \\ +ffiky\_ & \pageref{ffikyx} \\ +ffimem & \pageref{ffimem} \\ +ffinit & \pageref{ffinit} \\ +ffinttyp & \pageref{ffinttyp} \\ +ffiopn & \pageref{ffopen} \\ +ffirec & \pageref{ffirec} \\ + +\end{tabular} +\begin{tabular}{lr} + +ffirow & \pageref{ffirow} \\ +ffitab & \pageref{ffitab} \\ +ffiter & \pageref{ffiter} \\ +ffiurl & \pageref{ffiurl} \\ +ffkeyn & \pageref{ffkeyn} \\ +ffmahd & \pageref{ffmahd} \\ +ffmcom & \pageref{ffmcom} \\ +ffmcrd & \pageref{ffmcrd} \\ +ffmkls & \pageref{ffmkyx} \\ +ffmkyu & \pageref{ffmkyu} \\ +ffmky\_ & \pageref{ffmkyx} \\ +ffmnam & \pageref{ffmnam} \\ +ffmnhd & \pageref{ffmnhd} \\ +ffmrec & \pageref{ffmrec} \\ +ffmrhd & \pageref{ffmrhd} \\ +ffmvec & \pageref{ffmvec} \\ +ffnchk & \pageref{ffnchk} \\ +ffnkey & \pageref{ffnkey} \\ +ffomem & \pageref{ffomem} \\ +ffopen & \pageref{ffopen} \\ +ffp2d\_ & \pageref{ffp2dx} \\ +ffp3d\_ & \pageref{ffp3dx} \\ +ffpcks & \pageref{ffpcks} \\ +ffpcl & \pageref{ffpcl} \\ +ffpcls & \pageref{ffpcls} \\ +ffpcl\_ & \pageref{ffpclx} \\ +ffpclu & \pageref{ffpclu} \\ +ffpcn & \pageref{ffpcn} \\ +ffpcn\_ & \pageref{ffpcnx} \\ +ffpcom & \pageref{ffpcom} \\ +ffpdat & \pageref{ffpdat} \\ +ffpdes & \pageref{ffpdes} \\ +ffpextn & \pageref{ffgextn} \\ +ffpgp\_ & \pageref{ffpgpx} \\ +ffphbn & \pageref{ffphbn} \\ +ffphext & \pageref{ffphpr} \\ +ffphis & \pageref{ffphis} \\ +ffphpr & \pageref{ffphpr} \\ +ffphps & \pageref{ffphps} \\ +ffphtb & \pageref{ffphtb} \\ +ffpkls & \pageref{ffpkls} \\ +ffpkn\_ & \pageref{ffpknx} \\ +ffpktp & \pageref{ffpktp} \\ +ffpky & \pageref{ffpky} \\ +ffpkyt & \pageref{ffpkyt} \\ +ffpkyu & \pageref{ffpkyu} \\ +ffpky\_ & \pageref{ffpkyx} \\ +ffplsw & \pageref{ffplsw} \\ + +\end{tabular} +\begin{tabular}{lr} + +ffpmrk & \pageref{ffpmrk} \\ +ffpmsg & \pageref{ffpmsg} \\ +ffpnul & \pageref{ffpnul} \\ +ffppn & \pageref{ffppn} \\ +ffppn\_ & \pageref{ffppnx} \\ +ffppr & \pageref{ffppr} \\ +ffpprn & \pageref{ffpprn} \\ +ffppru & \pageref{ffppru} \\ +ffppr\_ & \pageref{ffpprx} \\ +ffppx & \pageref{ffppx} \\ +ffppxn & \pageref{ffppxn} \\ +ffprec & \pageref{ffprec} \\ +ffprwu & \pageref{ffpclu} \\ +ffpscl & \pageref{ffpscl} \\ +ffpss & \pageref{ffpss} \\ +ffpss\_ & \pageref{ffpssx} \\ +ffpsvc & \pageref{ffpsvc} \\ +ffptbb & \pageref{ffptbb} \\ +ffptdm & \pageref{ffptdm} \\ +ffpthp & \pageref{ffpthp} \\ +ffpunt & \pageref{ffpunt} \\ +ffrdef & \pageref{ffrdef} \\ +ffreopen & \pageref{ffreopen} \\ +ffrprt & \pageref{ffrprt} \\ +ffrsim & \pageref{ffrsim} \\ +ffrtnm & \pageref{ffrtnm} \\ +ffrwrg & \pageref{ffrwrg} \\ +ffs2dt & \pageref{ffdt2s} \\ +ffs2tm & \pageref{ffdt2s} \\ +ffsnul & \pageref{ffsnul} \\ +ffsrow & \pageref{ffsrow} \\ +fftexp & \pageref{fftexp} \\ +ffthdu & \pageref{ffthdu} \\ +fftheap & \pageref{fftheap} \\ +fftkey & \pageref{fftkey} \\ +fftm2s & \pageref{ffdt2s} \\ +fftnul & \pageref{fftnul} \\ +fftopn & \pageref{ffopen} \\ +fftplt & \pageref{fftplt} \\ +fftrec & \pageref{fftrec} \\ +fftscl & \pageref{fftscl} \\ +ffucrd & \pageref{ffucrd} \\ +ffukls & \pageref{ffukyx} \\ +ffuky & \pageref{ffuky} \\ +ffukyu & \pageref{ffukyu} \\ +ffuky\_ & \pageref{ffukyx} \\ +ffupch & \pageref{ffupch} \\ +ffupck & \pageref{ffupck} \\ + +\end{tabular} +\newpage +\begin{tabular}{lr} + +ffurlt & \pageref{ffurlt} \\ +ffvcks & \pageref{ffvcks} \\ +ffvers & \pageref{ffvers} \\ +ffwldp & \pageref{ffwldp} \\ +ffwrhdu & \pageref{ffwrhdu} \\ +ffxypx & \pageref{ffxypx} \\ + +\end{tabular} + + +*2 Parameter Definitions +- +anynul - set to TRUE (=1) if any returned values are undefined, else FALSE +array - array of numerical data values to read or write +ascii - encoded checksum string +binspec - the input table binning specifier +bitpix - bits per pixel. The following symbolic mnemonics are predefined: + BYTE_IMG = 8 (unsigned char) + SHORT_IMG = 16 (signed short integer) + LONG_IMG = 32 (signed long integer) + LONGLONG_IMG = 64 (signed long 64-bit integer) + FLOAT_IMG = -32 (float) + DOUBLE_IMG = -64 (double). + The LONGLONG_IMG type is experimental and is not officially + recognized in the FITS Standard document. + Two additional values, USHORT_IMG and ULONG_IMG are also available + for creating unsigned integer images. These are equivalent to + creating a signed integer image with BZERO offset keyword values + of 32768 or 2147483648, respectively, which is the convention that + FITS uses to store unsigned integers. +card - header record to be read or written (80 char max, null-terminated) +casesen - CASESEN (=1) for case-sensitive string matching, else CASEINSEN (=0) +cmopt - grouping table "compact" option parameter. Allowed values are: + OPT_CMT_MBR and OPT_CMT_MBR_DEL. +colname - name of the column (null-terminated) +colnum - column number (first column = 1) +colspec - the input file column specification; used to delete, create, or rename + table columns +comment - the keyword comment field (72 char max, null-terminated) +complm - should the checksum be complemented? +comptype - compression algorithm to use: GZIP_1, RICE_1, HCOMPRESS_1, or PLIO_1 +coordtype- type of coordinate projection (-SIN, -TAN, -ARC, -NCP, + -GLS, -MER, or -AIT) +cpopt - grouping table copy option parameter. Allowed values are: + OPT_GCP_GPT, OPT_GCP_MBR, OPT_GCP_ALL, OPT_MCP_ADD, OPT_MCP_NADD, + OPT_MCP_REPL, amd OPT_MCP_MOV. +create_col- If TRUE, then insert a new column in the table, otherwise + overwrite the existing column. +current - if TRUE, then the current HDU will be copied +dataok - was the data unit verification successful (=1) or + not (= -1). Equals zero if the DATASUM keyword is not present. +datasum - 32-bit 1's complement checksum for the data unit +dataend - address (in bytes) of the end of the HDU +datastart- address (in bytes) of the start of the data unit +datatype - specifies the data type of the value. Allowed value are: TSTRING, + TLOGICAL, TBYTE, TSBYTE, TSHORT, TUSHORT, TINT, TUINT, TLONG, TULONG, + TFLOAT, TDOUBLE, TCOMPLEX, and TDBLCOMPLEX +datestr - FITS date/time string: 'YYYY-MM-DDThh:mm:ss.ddd', 'YYYY-MM-dd', + or 'dd/mm/yy' +day - calendar day (UTC) (1-31) +decimals - number of decimal places to be displayed +deltasize - increment for allocating more memory +dim1 - declared size of the first dimension of the image or cube array +dim2 - declared size of the second dimension of the data cube array +dispwidth - display width of a column = length of string that will be read +dtype - data type of the keyword ('C', 'L', 'I', 'F' or 'X') + C = character string + L = logical + I = integer + F = floating point number + X = complex, e.g., "(1.23, -4.56)" +err_msg - error message on the internal stack (80 chars max) +err_text - error message string corresponding to error number (30 chars max) +exact - TRUE (=1) if the strings match exactly; + FALSE (=0) if wildcards are used +exclist - array of pointers to keyword names to be excluded from search +exists - flag indicating whether the file or compressed file exists on disk +expr - boolean or arithmetic expression +extend - TRUE (=1) if FITS file may have extensions, else FALSE (=0) +extname - value of the EXTNAME keyword (null-terminated) +extspec - the extension or HDU specifier; a number or name, version, and type +extver - value of the EXTVER keyword = integer version number +filename - full name of the FITS file, including optional HDU and filtering specs +filetype - type of file (file://, ftp://, http://, etc.) +filter - the input file filtering specifier +firstchar- starting byte in the row (first byte of row = 1) +firstfailed - member HDU ID (if positive) or grouping table GRPIDn index + value (if negative) that failed grouping table verification. +firstelem- first element in a vector (ignored for ASCII tables) +firstrow - starting row number (first row of table = 1) +following- if TRUE, any HDUs following the current HDU will be copied +fpixel - coordinate of the first pixel to be read or written in the + FITS array. The array must be of length NAXIS and have values such + that fpixel[0] is in the range 1 to NAXIS1, fpixel[1] is in the + range 1 to NAXIS2, etc. +fptr - pointer to a 'fitsfile' structure describing the FITS file. +frac - factional part of the keyword value +gcount - number of groups in the primary array (usually = 1) +gfptr - fitsfile* pointer to a grouping table HDU. +group - GRPIDn/GRPLCn index value identifying a grouping table HDU, or + data group number (=0 for non-grouped data) +grouptype - Grouping table parameter that specifies the columns to be + created in a grouping table HDU. Allowed values are: GT_ID_ALL_URI, + GT_ID_REF, GT_ID_POS, GT_ID_ALL, GT_ID_REF_URI, and GT_ID_POS_URI. +grpname - value to use for the GRPNAME keyword value. +hdunum - sequence number of the HDU (Primary array = 1) +hduok - was the HDU verification successful (=1) or + not (= -1). Equals zero if the CHECKSUM keyword is not present. +hdusum - 32 bit 1's complement checksum for the entire CHDU +hdutype - HDU type: IMAGE_HDU (0), ASCII_TBL (1), BINARY_TBL (2), ANY_HDU (-1) +header - returned character string containing all the keyword records +headstart- starting address (in bytes) of the CHDU +heapsize - size of the binary table heap, in bytes +history - the HISTORY keyword comment string (70 char max, null-terminated) +hour - hour within day (UTC) (0 - 23) +inc - sampling interval for pixels in each FITS dimension +inclist - array of pointers to matching keyword names +incolnum - input column number; range = 1 to TFIELDS +infile - the input filename, including path if specified +infptr - pointer to a 'fitsfile' structure describing the input FITS file. +intval - integer part of the keyword value +iomode - file access mode: either READONLY (=0) or READWRITE (=1) +keyname - name of a keyword (8 char max, null-terminated) +keynum - position of keyword in header (1st keyword = 1) +keyroot - root string for the keyword name (5 char max, null-terminated) +keysexist- number of existing keyword records in the CHU +keytype - header record type: -1=delete; 0=append or replace; + 1=append; 2=this is the END keyword +longstr - arbitrarily long string keyword value (null-terminated) +lpixel - coordinate of the last pixel to be read or written in the + FITS array. The array must be of length NAXIS and have values such + that lpixel[0] is in the range 1 to NAXIS1, lpixel[1] is in the + range 1 to NAXIS2, etc. +match - TRUE (=1) if the 2 strings match, else FALSE (=0) +maxdim - maximum number of values to return +member - row number of a grouping table member HDU. +memptr - pointer to the a FITS file in memory +mem_realloc - pointer to a function for reallocating more memory +memsize - size of the memory block allocated for the FITS file +mfptr - fitsfile* pointer to a grouping table member HDU. +mgopt - grouping table merge option parameter. Allowed values are: + OPT_MRG_COPY, and OPT_MRG_MOV. +minute - minute within hour (UTC) (0 - 59) +month - calendar month (UTC) (1 - 12) +morekeys - space in the header for this many more keywords +n_good_rows - number of rows evaluating to TRUE +namelist - string containing a comma or space delimited list of names +naxes - size of each dimension in the FITS array +naxis - number of dimensions in the FITS array +naxis1 - length of the X/first axis of the FITS array +naxis2 - length of the Y/second axis of the FITS array +naxis3 - length of the Z/third axis of the FITS array +nbytes - number of bytes or characters to read or write +nchars - number of characters to read or write +nelements- number of data elements to read or write +newfptr - returned pointer to the reopened file +newveclen- new value for the column vector repeat parameter +nexc - number of names in the exclusion list (may = 0) +nfound - number of keywords found (highest keyword number) +nkeys - number of keywords in the sequence +ninc - number of names in the inclusion list +nmembers - Number of grouping table members (NAXIS2 value). +nmove - number of HDUs to move (+ or -), relative to current position +nocomments - if equal to TRUE, then no commentary keywords will be copied +noisebits- number of bits to ignore when compressing floating point images +nrows - number of rows in the table +nstart - first integer value +nullarray- set to TRUE (=1) if corresponding data element is undefined +nulval - numerical value to represent undefined pixels +nulstr - character string used to represent undefined values in ASCII table +numval - numerical data value, of the appropriate data type +offset - byte offset in the heap or data unit to the first element of the vector +openfptr - pointer to a currently open FITS file +overlap - number of bytes in the binary table heap pointed to by more than 1 + descriptor +outcolnum- output column number; range = 1 to TFIELDS + 1 +outfile - and optional output filename; the input file will be copied to this prior + to opening the file +outfptr - pointer to a 'fitsfile' structure describing the output FITS file. +pcount - value of the PCOUNT keyword = size of binary table heap +previous - if TRUE, any previous HDUs in the input file will be copied. +repeat - length of column vector (e.g. 12J); == 1 for ASCII table +rmopt - grouping table remove option parameter. Allowed values are: + OPT_RM_GPT, OPT_RM_ENTRY, OPT_RM_MBR, and OPT_RM_ALL. +rootname - root filename, minus any extension or filtering specifications +rot - celestial coordinate rotation angle (degrees) +rowlen - length of a table row, in characters or bytes +rowlist - sorted list of row numbers to be deleted from the table +rownum - number of the row (first row = 1) +rowrange - list of rows or row ranges: '3,6-8,12,56-80' or '500-' +row_status - array of True/False results for each row that was evaluated +scale - linear scaling factor; true value = (FITS value) * scale + zero +second - second within minute (0 - 60.9999999999) (leap second!) +section - section of image to be copied (e.g. 21:80,101:200) +simple - TRUE (=1) if FITS file conforms to the Standard, else FALSE (=0) +space - number of blank spaces to leave between ASCII table columns +status - returned error status code (0 = OK) +sum - 32 bit unsigned checksum value +tbcol - byte position in row to start of column (1st col has tbcol = 1) +tdisp - Fortran style display format for the table column +tdimstr - the value of the TDIMn keyword +templt - template string used in comparison (null-terminated) +tfields - number of fields (columns) in the table +tfopt - grouping table member transfer option parameter. Allowed values are: + OPT_MCP_ADD, and OPT_MCP_MOV. +tform - format of the column (null-terminated); allowed values are: + ASCII tables: Iw, Aw, Fww.dd, Eww.dd, or Dww.dd + Binary tables: rL, rX, rB, rI, rJ, rA, rAw, rE, rD, rC, rM + where 'w'=width of the field, 'd'=no. of decimals, 'r'=repeat count. + Variable length array columns are denoted by a '1P' before the data type + character (e.g., '1PJ'). When creating a binary table, 2 addition tform + data type codes are recognized by CFITSIO: 'rU' and 'rV' for unsigned + 16-bit and unsigned 32-bit integer, respectively. + +theap - zero indexed byte offset of starting address of the heap + relative to the beginning of the binary table data +tilesize - array of length NAXIS that specifies the dimensions of + the image compression tiles +ttype - label or name for table column (null-terminated) +tunit - physical unit for table column (null-terminated) +typechar - symbolic code of the table column data type +typecode - data type code of the table column. The negative of + the value indicates a variable length array column. + Datatype typecode Mnemonic + bit, X 1 TBIT + byte, B 11 TBYTE + logical, L 14 TLOGICAL + ASCII character, A 16 TSTRING + short integer, I 21 TSHORT + integer, J 41 TINT32BIT (same as TLONG) + long long integer, K 81 TLONGLONG + real, E 42 TFLOAT + double precision, D 82 TDOUBLE + complex, C 83 TCOMPLEX + double complex, M 163 TDBLCOMPLEX +unit - the physical unit string (e.g., 'km/s') for a keyword +unused - number of unused bytes in the binary table heap +urltype - the file type of the FITS file (file://, ftp://, mem://, etc.) +validheap- returned value = FALSE if any of the variable length array + address are outside the valid range of addresses in the heap +value - the keyword value string (70 char max, null-terminated) +version - current version number of the CFITSIO library +width - width of the character string field +xcol - number of the column containing the X coordinate values +xinc - X axis coordinate increment at reference pixel (deg) +xpix - X axis pixel location +xpos - X axis celestial coordinate (usually RA) (deg) +xrefpix - X axis reference pixel array location +xrefval - X axis coordinate value at the reference pixel (deg) +ycol - number of the column containing the X coordinate values +year - calendar year (e.g. 1999, 2000, etc) +yinc - Y axis coordinate increment at reference pixel (deg) +ypix - y axis pixel location +ypos - y axis celestial coordinate (usually DEC) (deg) +yrefpix - Y axis reference pixel array location +yrefval - Y axis coordinate value at the reference pixel (deg) +zero - scaling offset; true value = (FITS value) * scale + zero +- + +*3 CFITSIO Error Status Codes + +The following table lists all the error status codes used by CFITSIO. +Programmers are encouraged to use the symbolic mnemonics (defined in +the file fitsio.h) rather than the actual integer status values to +improve the readability of their code. +- + Symbolic Const Value Meaning + -------------- ----- ----------------------------------------- + 0 OK, no error + SAME_FILE 101 input and output files are the same + TOO_MANY_FILES 103 tried to open too many FITS files at once + FILE_NOT_OPENED 104 could not open the named file + FILE_NOT_CREATED 105 could not create the named file + WRITE_ERROR 106 error writing to FITS file + END_OF_FILE 107 tried to move past end of file + READ_ERROR 108 error reading from FITS file + FILE_NOT_CLOSED 110 could not close the file + ARRAY_TOO_BIG 111 array dimensions exceed internal limit + READONLY_FILE 112 Cannot write to readonly file + MEMORY_ALLOCATION 113 Could not allocate memory + BAD_FILEPTR 114 invalid fitsfile pointer + NULL_INPUT_PTR 115 NULL input pointer to routine + SEEK_ERROR 116 error seeking position in file + + BAD_URL_PREFIX 121 invalid URL prefix on file name + TOO_MANY_DRIVERS 122 tried to register too many IO drivers + DRIVER_INIT_FAILED 123 driver initialization failed + NO_MATCHING_DRIVER 124 matching driver is not registered + URL_PARSE_ERROR 125 failed to parse input file URL + RANGE_PARSE_ERROR 126 parse error in range list + + SHARED_BADARG 151 bad argument in shared memory driver + SHARED_NULPTR 152 null pointer passed as an argument + SHARED_TABFULL 153 no more free shared memory handles + SHARED_NOTINIT 154 shared memory driver is not initialized + SHARED_IPCERR 155 IPC error returned by a system call + SHARED_NOMEM 156 no memory in shared memory driver + SHARED_AGAIN 157 resource deadlock would occur + SHARED_NOFILE 158 attempt to open/create lock file failed + SHARED_NORESIZE 159 shared memory block cannot be resized at the moment + + HEADER_NOT_EMPTY 201 header already contains keywords + KEY_NO_EXIST 202 keyword not found in header + KEY_OUT_BOUNDS 203 keyword record number is out of bounds + VALUE_UNDEFINED 204 keyword value field is blank + NO_QUOTE 205 string is missing the closing quote + BAD_INDEX_KEY 206 illegal indexed keyword name (e.g. 'TFORM1000') + BAD_KEYCHAR 207 illegal character in keyword name or card + BAD_ORDER 208 required keywords out of order + NOT_POS_INT 209 keyword value is not a positive integer + NO_END 210 couldn't find END keyword + BAD_BITPIX 211 illegal BITPIX keyword value + BAD_NAXIS 212 illegal NAXIS keyword value + BAD_NAXES 213 illegal NAXISn keyword value + BAD_PCOUNT 214 illegal PCOUNT keyword value + BAD_GCOUNT 215 illegal GCOUNT keyword value + BAD_TFIELDS 216 illegal TFIELDS keyword value + NEG_WIDTH 217 negative table row size + NEG_ROWS 218 negative number of rows in table + COL_NOT_FOUND 219 column with this name not found in table + BAD_SIMPLE 220 illegal value of SIMPLE keyword + NO_SIMPLE 221 Primary array doesn't start with SIMPLE + NO_BITPIX 222 Second keyword not BITPIX + NO_NAXIS 223 Third keyword not NAXIS + NO_NAXES 224 Couldn't find all the NAXISn keywords + NO_XTENSION 225 HDU doesn't start with XTENSION keyword + NOT_ATABLE 226 the CHDU is not an ASCII table extension + NOT_BTABLE 227 the CHDU is not a binary table extension + NO_PCOUNT 228 couldn't find PCOUNT keyword + NO_GCOUNT 229 couldn't find GCOUNT keyword + NO_TFIELDS 230 couldn't find TFIELDS keyword + NO_TBCOL 231 couldn't find TBCOLn keyword + NO_TFORM 232 couldn't find TFORMn keyword + NOT_IMAGE 233 the CHDU is not an IMAGE extension + BAD_TBCOL 234 TBCOLn keyword value < 0 or > rowlength + NOT_TABLE 235 the CHDU is not a table + COL_TOO_WIDE 236 column is too wide to fit in table + COL_NOT_UNIQUE 237 more than 1 column name matches template + BAD_ROW_WIDTH 241 sum of column widths not = NAXIS1 + UNKNOWN_EXT 251 unrecognizable FITS extension type + UNKNOWN_REC 252 unknown record; 1st keyword not SIMPLE or XTENSION + END_JUNK 253 END keyword is not blank + BAD_HEADER_FILL 254 Header fill area contains non-blank chars + BAD_DATA_FILL 255 Illegal data fill bytes (not zero or blank) + BAD_TFORM 261 illegal TFORM format code + BAD_TFORM_DTYPE 262 unrecognizable TFORM data type code + BAD_TDIM 263 illegal TDIMn keyword value + BAD_HEAP_PTR 264 invalid BINTABLE heap pointer is out of range + + BAD_HDU_NUM 301 HDU number < 1 + BAD_COL_NUM 302 column number < 1 or > tfields + NEG_FILE_POS 304 tried to move to negative byte location in file + NEG_BYTES 306 tried to read or write negative number of bytes + BAD_ROW_NUM 307 illegal starting row number in table + BAD_ELEM_NUM 308 illegal starting element number in vector + NOT_ASCII_COL 309 this is not an ASCII string column + NOT_LOGICAL_COL 310 this is not a logical data type column + BAD_ATABLE_FORMAT 311 ASCII table column has wrong format + BAD_BTABLE_FORMAT 312 Binary table column has wrong format + NO_NULL 314 null value has not been defined + NOT_VARI_LEN 317 this is not a variable length column + BAD_DIMEN 320 illegal number of dimensions in array + BAD_PIX_NUM 321 first pixel number greater than last pixel + ZERO_SCALE 322 illegal BSCALE or TSCALn keyword = 0 + NEG_AXIS 323 illegal axis length < 1 + + NOT_GROUP_TABLE 340 Grouping function error + HDU_ALREADY_MEMBER 341 + MEMBER_NOT_FOUND 342 + GROUP_NOT_FOUND 343 + BAD_GROUP_ID 344 + TOO_MANY_HDUS_TRACKED 345 + HDU_ALREADY_TRACKED 346 + BAD_OPTION 347 + IDENTICAL_POINTERS 348 + BAD_GROUP_ATTACH 349 + BAD_GROUP_DETACH 350 + + NGP_NO_MEMORY 360 malloc failed + NGP_READ_ERR 361 read error from file + NGP_NUL_PTR 362 null pointer passed as an argument. + Passing null pointer as a name of + template file raises this error + NGP_EMPTY_CURLINE 363 line read seems to be empty (used + internally) + NGP_UNREAD_QUEUE_FULL 364 cannot unread more then 1 line (or single + line twice) + NGP_INC_NESTING 365 too deep include file nesting (infinite + loop, template includes itself ?) + NGP_ERR_FOPEN 366 fopen() failed, cannot open template file + NGP_EOF 367 end of file encountered and not expected + NGP_BAD_ARG 368 bad arguments passed. Usually means + internal parser error. Should not happen + NGP_TOKEN_NOT_EXPECT 369 token not expected here + + BAD_I2C 401 bad int to formatted string conversion + BAD_F2C 402 bad float to formatted string conversion + BAD_INTKEY 403 can't interpret keyword value as integer + BAD_LOGICALKEY 404 can't interpret keyword value as logical + BAD_FLOATKEY 405 can't interpret keyword value as float + BAD_DOUBLEKEY 406 can't interpret keyword value as double + BAD_C2I 407 bad formatted string to int conversion + BAD_C2F 408 bad formatted string to float conversion + BAD_C2D 409 bad formatted string to double conversion + BAD_DATATYPE 410 illegal datatype code value + BAD_DECIM 411 bad number of decimal places specified + NUM_OVERFLOW 412 overflow during data type conversion + DATA_COMPRESSION_ERR 413 error compressing image + DATA_DECOMPRESSION_ERR 414 error uncompressing image + + BAD_DATE 420 error in date or time conversion + + PARSE_SYNTAX_ERR 431 syntax error in parser expression + PARSE_BAD_TYPE 432 expression did not evaluate to desired type + PARSE_LRG_VECTOR 433 vector result too large to return in array + PARSE_NO_OUTPUT 434 data parser failed not sent an out column + PARSE_BAD_COL 435 bad data encounter while parsing column + PARSE_BAD_OUTPUT 436 Output file not of proper type + + ANGLE_TOO_BIG 501 celestial angle too large for projection + BAD_WCS_VAL 502 bad celestial coordinate or pixel value + WCS_ERROR 503 error in celestial coordinate calculation + BAD_WCS_PROJ 504 unsupported type of celestial projection + NO_WCS_KEY 505 celestial coordinate keywords not found + APPROX_WCS_KEY 506 approximate wcs keyword values were returned +- +\end{document} + |