1 /*- 2 * Copyright (c) 2007 Dag-Erling Coïdan Smørgrav 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer 10 * in this position and unchanged. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 * 27 * $FreeBSD: src/lib/libutil/flopen.c,v 1.11 2008/10/20 18:11:30 des Exp $ 28 */ 29 30 #include <sys/stat.h> 31 32 #include <errno.h> 33 #include <fcntl.h> 34 #include <stdarg.h> 35 #include <string.h> 36 #include <unistd.h> 37 38 #include <libutil.h> 39 40 int 41 flopen(const char *path, int flags, ...) 42 { 43 int fd, operation, serrno, trunc; 44 struct flock lock; 45 struct stat sb, fsb; 46 mode_t mode; 47 48 #ifdef O_EXLOCK 49 flags &= ~O_EXLOCK; 50 #endif 51 52 mode = 0; 53 if (flags & O_CREAT) { 54 va_list ap; 55 56 va_start(ap, flags); 57 mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */ 58 va_end(ap); 59 } 60 61 memset(&lock, 0, sizeof lock); 62 lock.l_type = ((flags & O_ACCMODE) == O_RDONLY) ? F_RDLCK : F_WRLCK; 63 lock.l_whence = SEEK_SET; 64 operation = (flags & O_NONBLOCK) ? F_SETLK : F_SETLKW; 65 66 trunc = (flags & O_TRUNC); 67 flags &= ~O_TRUNC; 68 69 for (;;) { 70 if ((fd = open(path, flags, mode)) == -1) 71 /* non-existent or no access */ 72 return (-1); 73 if (fcntl(fd, operation, &lock) == -1) { 74 /* unsupported or interrupted */ 75 serrno = errno; 76 close(fd); 77 errno = serrno; 78 return (-1); 79 } 80 if (stat(path, &sb) == -1) { 81 /* disappeared from under our feet */ 82 close(fd); 83 continue; 84 } 85 if (fstat(fd, &fsb) == -1) { 86 /* can't happen [tm] */ 87 serrno = errno; 88 close(fd); 89 errno = serrno; 90 return (-1); 91 } 92 if (sb.st_dev != fsb.st_dev || 93 sb.st_ino != fsb.st_ino) { 94 /* changed under our feet */ 95 close(fd); 96 continue; 97 } 98 if (trunc && ftruncate(fd, 0) != 0) { 99 /* can't happen [tm] */ 100 serrno = errno; 101 close(fd); 102 errno = serrno; 103 return (-1); 104 } 105 return (fd); 106 } 107 } 108