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77 lines
1.4 KiB
C
77 lines
1.4 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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#ifdef 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 (fd, length)
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int fd;
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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
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#ifdef F_FREESP
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/* The following function was written by
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kucharsk@Solbourne.com (William Kucharski) */
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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 (fd, length)
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int fd;
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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
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fcntl, which truncates the file so that it ends at the
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position indicated by fl.l_start.
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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
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int
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ftruncate (fd, length)
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int fd;
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off_t length;
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{
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return chsize (fd, length);
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}
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#endif
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#endif
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