1 /* ftruncate emulations that work on some System V's. 2 This file is in the public domain. */ 3 4 /* Copyright (C) 2012-2016 Free Software Foundation, Inc. 5 6 This file is part of gold. 7 8 This program is free software; you can redistribute it and/or modify 9 it under the terms of the GNU General Public License as published by 10 the Free Software Foundation; either version 3 of the License, or 11 (at your option) any later version. 12 13 This program is distributed in the hope that it will be useful, 14 but WITHOUT ANY WARRANTY; without even the implied warranty of 15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 GNU General Public License for more details. 17 18 You should have received a copy of the GNU General Public License 19 along with this program; if not, write to the Free Software 20 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, 21 MA 02110-1301, USA. */ 22 23 #include <config.h> 24 25 /* Specification. */ 26 #include <unistd.h> 27 28 #include <sys/types.h> 29 #include <fcntl.h> 30 31 extern int ftruncate (int, off_t); 32 33 #ifdef F_CHSIZE 34 35 int 36 ftruncate (int fd, off_t length) 37 { 38 return fcntl (fd, F_CHSIZE, length); 39 } 40 41 #else /* not F_CHSIZE */ 42 # ifdef F_FREESP 43 44 /* By William Kucharski <kucharsk (at) netcom.com>. */ 45 46 # include <sys/stat.h> 47 # include <errno.h> 48 49 int 50 ftruncate (int fd, off_t length) 51 { 52 struct flock fl; 53 struct stat filebuf; 54 55 if (fstat (fd, &filebuf) < 0) 56 return -1; 57 58 if (filebuf.st_size < length) 59 { 60 /* Extend file length. */ 61 if (lseek (fd, (length - 1), SEEK_SET) < 0) 62 return -1; 63 64 /* Write a "0" byte. */ 65 if (write (fd, "", 1) != 1) 66 return -1; 67 } 68 else 69 { 70 71 /* Truncate length. */ 72 73 fl.l_whence = 0; 74 fl.l_len = 0; 75 fl.l_start = length; 76 fl.l_type = F_WRLCK; /* write lock on file space */ 77 78 /* This relies on the *undocumented* F_FREESP argument to fcntl, 79 which truncates the file so that it ends at the position 80 indicated by fl.l_start. Will minor miracles never cease? */ 81 82 if (fcntl (fd, F_FREESP, &fl) < 0) 83 return -1; 84 } 85 86 return 0; 87 } 88 89 # else /* not F_CHSIZE nor F_FREESP */ 90 # if HAVE_CHSIZE /* native Windows, e.g. mingw */ 91 92 int 93 ftruncate (int fd, off_t length) 94 { 95 return chsize (fd, length); 96 } 97 98 # else /* not F_CHSIZE nor F_FREESP nor HAVE_CHSIZE */ 99 100 # include <errno.h> 101 102 int 103 ftruncate (int fd, off_t length) 104 { 105 errno = EIO; 106 return -1; 107 } 108 109 # endif /* not HAVE_CHSIZE */ 110 # endif /* not F_FREESP */ 111 #endif /* not F_CHSIZE */ 112
