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/* ftruncate emulations that work on some System V's.
   This file is in the public domain.  */
 
#include <config.h>
 
/* Specification.  */
#include <unistd.h>
 
#include <sys/types.h>
#include <fcntl.h>
 
extern int ftruncate (int, off_t);
 
#ifdef F_CHSIZE
 
int
ftruncate (int fd, off_t length)
{
  return fcntl (fd, F_CHSIZE, length);
}
 
#else /* not F_CHSIZE */
# ifdef F_FREESP
 
/* By William Kucharski <kucharsk@netcom.com>.  */
 
#  include <sys/stat.h>
#  include <errno.h>
 
int
ftruncate (int fd, off_t length)
{
  struct flock fl;
  struct stat filebuf;
 
  if (fstat (fd, &filebuf) < 0)
    return -1;
 
  if (filebuf.st_size < length)
    {
      /* Extend file length. */
      if (lseek (fd, (length - 1), SEEK_SET) < 0)
	return -1;
 
      /* Write a "0" byte. */
      if (write (fd, "", 1) != 1)
	return -1;
    }
  else
    {
 
      /* Truncate length. */
 
      fl.l_whence = 0;
      fl.l_len = 0;
      fl.l_start = length;
      fl.l_type = F_WRLCK;	/* write lock on file space */
 
      /* This relies on the *undocumented* F_FREESP argument to fcntl,
	 which truncates the file so that it ends at the position
	 indicated by fl.l_start.  Will minor miracles never cease?  */
 
      if (fcntl (fd, F_FREESP, &fl) < 0)
	return -1;
    }
 
  return 0;
}
 
# else /* not F_CHSIZE nor F_FREESP */
#  if HAVE_CHSIZE                      /* native Windows, e.g. mingw */
 
int
ftruncate (int fd, off_t length)
{
  return chsize (fd, length);
}
 
#  else /* not F_CHSIZE nor F_FREESP nor HAVE_CHSIZE */
 
#   include <errno.h>
 
int
ftruncate (int fd, off_t length)
{
  errno = EIO;
  return -1;
}
 
#  endif /* not HAVE_CHSIZE */
# endif /* not F_FREESP */
#endif /* not F_CHSIZE */