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/* ftruncate emulations that work on some System V's.
This file is in the public domain. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <sys/types.h>
#include <fcntl.h>
#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>
# include <unistd.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
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 */
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