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annotate lib/ftruncate.c @ 12421:e8d2c6fc33ad

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Use spaces for indentation, not tabs.
author Bruno Haible <bruno@clisp.org>
date Thu, 10 Dec 2009 20:28:30 +0100
parents 717accda417a
children 9f82d16d3139
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 /* ftruncate emulations that work on some System V's.
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2 This file is in the public domain. */
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3
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4 #include <config.h>
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6 /* Specification. */
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7 #include <unistd.h>
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8
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9 #include <sys/types.h>
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10 #include <fcntl.h>
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12 #ifdef F_CHSIZE
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14 int
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15 ftruncate (int fd, off_t length)
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16 {
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17 return fcntl (fd, F_CHSIZE, length);
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18 }
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19
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20 #else /* not F_CHSIZE */
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21 # ifdef F_FREESP
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22
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23 /* By William Kucharski <kucharsk@netcom.com>. */
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24
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25 # include <sys/stat.h>
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26 # include <errno.h>
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28 int
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29 ftruncate (int fd, off_t length)
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30 {
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31 struct flock fl;
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32 struct stat filebuf;
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33
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34 if (fstat (fd, &filebuf) < 0)
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35 return -1;
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36
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37 if (filebuf.st_size < length)
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38 {
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39 /* Extend file length. */
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40 if (lseek (fd, (length - 1), SEEK_SET) < 0)
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41 return -1;
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42
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43 /* Write a "0" byte. */
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44 if (write (fd, "", 1) != 1)
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45 return -1;
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46 }
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47 else
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48 {
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49
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50 /* Truncate length. */
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51
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52 fl.l_whence = 0;
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53 fl.l_len = 0;
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54 fl.l_start = length;
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55 fl.l_type = F_WRLCK; /* write lock on file space */
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56
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57 /* This relies on the *undocumented* F_FREESP argument to fcntl,
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58 which truncates the file so that it ends at the position
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59 indicated by fl.l_start. Will minor miracles never cease? */
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61 if (fcntl (fd, F_FREESP, &fl) < 0)
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62 return -1;
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63 }
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65 return 0;
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66 }
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68 # else /* not F_CHSIZE nor F_FREESP */
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69 # if HAVE_CHSIZE /* native Windows, e.g. mingw */
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70
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71 int
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72 ftruncate (int fd, off_t length)
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73 {
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74 return chsize (fd, length);
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75 }
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77 # else /* not F_CHSIZE nor F_FREESP nor HAVE_CHSIZE */
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78
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79 # include <errno.h>
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80
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81 int
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82 ftruncate (int fd, off_t length)
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83 {
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84 errno = EIO;
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85 return -1;
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86 }
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88 # endif /* not HAVE_CHSIZE */
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89 # endif /* not F_FREESP */
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90 #endif /* not F_CHSIZE */