| 1 | /* ftruncate emulations that work on some System V's. |
| 2 | This file is in the public domain. */ |
| 3 | |
| 4 | #include <config.h> |
| 5 | |
| 6 | /* Specification. */ |
| 7 | #include <unistd.h> |
| 8 | |
| 9 | #include <sys/types.h> |
| 10 | #include <fcntl.h> |
| 11 | |
| 12 | extern int ftruncate (int, off_t); |
| 13 | |
| 14 | #ifdef F_CHSIZE |
| 15 | |
| 16 | int |
| 17 | ftruncate (int fd, off_t length) |
| 18 | { |
| 19 | return fcntl (fd, F_CHSIZE, length); |
| 20 | } |
| 21 | |
| 22 | #else /* not F_CHSIZE */ |
| 23 | # ifdef F_FREESP |
| 24 | |
| 25 | /* By William Kucharski <kucharsk@netcom.com>. */ |
| 26 | |
| 27 | # include <sys/stat.h> |
| 28 | # include <errno.h> |
| 29 | |
| 30 | int |
| 31 | ftruncate (int fd, off_t length) |
| 32 | { |
| 33 | struct flock fl; |
| 34 | struct stat filebuf; |
| 35 | |
| 36 | if (fstat (fd, &filebuf) < 0) |
| 37 | return -1; |
| 38 | |
| 39 | if (filebuf.st_size < length) |
| 40 | { |
| 41 | /* Extend file length. */ |
| 42 | if (lseek (fd, (length - 1), SEEK_SET) < 0) |
| 43 | return -1; |
| 44 | |
| 45 | /* Write a "0" byte. */ |
| 46 | if (write (fd, "", 1) != 1) |
| 47 | return -1; |
| 48 | } |
| 49 | else |
| 50 | { |
| 51 | |
| 52 | /* Truncate length. */ |
| 53 | |
| 54 | fl.l_whence = 0; |
| 55 | fl.l_len = 0; |
| 56 | fl.l_start = length; |
| 57 | fl.l_type = F_WRLCK; /* write lock on file space */ |
| 58 | |
| 59 | /* This relies on the *undocumented* F_FREESP argument to fcntl, |
| 60 | which truncates the file so that it ends at the position |
| 61 | indicated by fl.l_start. Will minor miracles never cease? */ |
| 62 | |
| 63 | if (fcntl (fd, F_FREESP, &fl) < 0) |
| 64 | return -1; |
| 65 | } |
| 66 | |
| 67 | return 0; |
| 68 | } |
| 69 | |
| 70 | # else /* not F_CHSIZE nor F_FREESP */ |
| 71 | # if HAVE_CHSIZE /* native Windows, e.g. mingw */ |
| 72 | |
| 73 | int |
| 74 | ftruncate (int fd, off_t length) |
| 75 | { |
| 76 | return chsize (fd, length); |
| 77 | } |
| 78 | |
| 79 | # else /* not F_CHSIZE nor F_FREESP nor HAVE_CHSIZE */ |
| 80 | |
| 81 | # include <errno.h> |
| 82 | |
| 83 | int |
| 84 | ftruncate (int fd, off_t length) |
| 85 | { |
| 86 | errno = EIO; |
| 87 | return -1; |
| 88 | } |
| 89 | |
| 90 | # endif /* not HAVE_CHSIZE */ |
| 91 | # endif /* not F_FREESP */ |
| 92 | #endif /* not F_CHSIZE */ |