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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <fset.h>
include <imio.h>
define SZ_ZBUF 50
# IMWRITE -- Write data to the pixel storage file. Bounds checking has
# already been performed by the time IMWRITE is called. If writing beyond
# EOF (new image), write zeros until the indicated offset is reached.
procedure imwrite (imdes, buf, nchars, offset)
pointer imdes
char buf[ARB]
int nchars
long offset
int fd
char zbuf[SZ_ZBUF]
long start, i
long fstatl()
errchk write, seek, fstatl
data zbuf /SZ_ZBUF*0,0/
begin
fd = IM_PFD(imdes)
# Get file size. If writing beyond end of file (file_size+1),
# write out blocks of zeros until the desired offset is reached.
# The IM_FILESIZE parameter in the image descriptor is not always
# up to date, but does provide a lower bound on the size of the pixel
# storage file.
if (offset >= IM_FILESIZE(imdes))
IM_FILESIZE(imdes) = fstatl (fd, F_FILESIZE)
if (offset-1 <= IM_FILESIZE(imdes)) {
# Write within bounds of file, or at EOF.
call seek (fd, offset)
call write (fd, buf, nchars)
} else {
# Write beyond EOF.
IM_FILESIZE(imdes) = fstatl (fd, F_FILESIZE)
start = IM_FILESIZE(imdes) + 1
call seek (fd, start)
do i = start, offset, SZ_ZBUF
call write (fd, zbuf, min (SZ_ZBUF, offset-i))
call write (fd, buf, nchars)
IM_FILESIZE(imdes) = fstatl (fd, F_FILESIZE)
}
end
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