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