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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 */