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C--------------------------------------------------------------------------
subroutine ftrhdu(iunit,xtend,status)
C read the CHDU structure by reading the header keywords which define
C the size and structure of the header and data units.
C iunit i Fortran I/O unit number
C OUTPUT PARAMETERS:
C xtend i returned type of extension: 0 = the primary HDU
C 1 = an ASCII table
C 2 = a binary table
C -1 = unknown
C status i returned error status (0=ok)
C
C written by Wm Pence, HEASARC/GSFC, June 1991
integer iunit,xtend,status,i,ic,tstat
character keynam*8,exttyp*10,comm*30,keybuf*80
logical endof
if (status .gt. 0)return
C read first keyword to determine the type of the CHDU
call ftgrec(iunit,1,keybuf,status)
if (status .gt. 0)then
call ftpmsg('Cannot read first keyword in header (FTRHDU)')
return
end if
C release any current column descriptors for this unit
call ftfrcl(iunit,status)
keynam=keybuf(1:8)
C parse the value and comment fields from the record
call ftpsvc(keybuf,exttyp,comm,status)
if (status .gt. 0)then
C unknown type of FITS record; can't read it
call ftpmsg('Cannot parse value of first keyword; unknown '
& //'type of FITS record (FTRHDU):')
else if (keynam .eq. 'SIMPLE')then
C initialize the parameters describing the primay HDU
call ftpini(iunit,status)
xtend=0
else if (keynam.eq.'XTENSION')then
if (exttyp(1:1) .ne. '''')then
C value of XTENSION is not a quoted character string!
if (keybuf(9:10) .ne. '= ')then
call ftpmsg('XTENSION keyword does not '
& //'have "= " in cols 9-10.')
else
call ftpmsg('Unknown type of extension; value'
& //' of XTENSION keyword is not a quoted string:')
end if
status=251
call ftpmsg(keybuf)
else if (exttyp(2:9) .eq. 'TABLE ')then
C initialize the parameters for the ASCII table extension
call ftaini(iunit,status)
xtend=1
else if (exttyp(2:9) .eq. 'BINTABLE' .or. exttyp(2:9)
& .eq. 'A3DTABLE' .or. exttyp(2:9) .eq. '3DTABLE ')then
C initialize the parameters for the binary table extension
call ftbini(iunit,status)
xtend=2
else
C try to initialize the parameters describing extension
tstat=status
call ftpini(iunit,status)
xtend=0
if (status .eq. 251)then
C unknown type of extension
xtend=-1
status=tstat
end if
end if
else
C unknown record
C If file is created on a VAX with 512-byte records, then
C the FITS file may have fill bytes (ASCII NULs) at the end.
C Also, if file has been editted on a SUN, an extra ASCII 10
C character may appear at the end of the file. Finally, if
C file is not a multiple of the record length long, then
C the last truncated record may be filled with ASCII blanks.
C So, if the record only contains NULS, LF, and blanks, then
C assume we found the end of file. Otherwise report an error.
endof=.true.
do 10 i=1,80
ic=ichar(keybuf(i:i))
if (ic .ne. 0 .and .ic .ne. 10 .and. ic .ne. 32)
& endof=.false.
10 continue
if (endof)then
status=107
call ftpmsg('ASCII 0s, 10s, or 32s at start of '
& //'extension are treated as EOF (FTRHDU):')
else
status=252
call ftpmsg('Extension does not start with SIMPLE'
& //' or XTENSION keyword (FTRHDU):')
end if
xtend=-1
call ftpmsg(keybuf)
end if
end
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