1/* ftruncate emulations that work on some System V's. 2 This file is in the public domain. */ 3 4/* Copyright (C) 2012-2024 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 31extern int ftruncate (int, off_t); 32 33#ifdef F_CHSIZE 34 35int 36ftruncate (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@netcom.com>. */ 45 46# include <sys/stat.h> 47# include <errno.h> 48 49int 50ftruncate (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 92int 93ftruncate (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 102int 103ftruncate (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