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 28 #include <sys/cdefs.h> 29 __FBSDID("$FreeBSD$"); 30 31 #include <sys/stat.h> 32 33 #include <errno.h> 34 #include <fcntl.h> 35 #include <stdarg.h> 36 #include <string.h> 37 #include <unistd.h> 38 39 #include <libutil.h> 40 41 int 42 flopen(const char *path, int flags, ...) 43 { 44 int fd, operation, serrno, trunc; 45 struct flock lock; 46 struct stat sb, fsb; 47 mode_t mode; 48 49 #ifdef O_EXLOCK 50 flags &= ~O_EXLOCK; 51 #endif 52 53 mode = 0; 54 if (flags & O_CREAT) { 55 va_list ap; 56 57 va_start(ap, flags); 58 mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */ 59 va_end(ap); 60 } 61 62 memset(&lock, 0, sizeof lock); 63 lock.l_type = ((flags & O_ACCMODE) == O_RDONLY) ? F_RDLCK : F_WRLCK; 64 lock.l_whence = SEEK_SET; 65 operation = (flags & O_NONBLOCK) ? F_SETLK : F_SETLKW; 66 67 trunc = (flags & O_TRUNC); 68 flags &= ~O_TRUNC; 69 70 for (;;) { 71 if ((fd = open(path, flags, mode)) == -1) 72 /* non-existent or no access */ 73 return (-1); 74 if (fcntl(fd, operation, &lock) == -1) { 75 /* unsupported or interrupted */ 76 serrno = errno; 77 (void)close(fd); 78 errno = serrno; 79 return (-1); 80 } 81 if (stat(path, &sb) == -1) { 82 /* disappeared from under our feet */ 83 (void)close(fd); 84 continue; 85 } 86 if (fstat(fd, &fsb) == -1) { 87 /* can't happen [tm] */ 88 serrno = errno; 89 (void)close(fd); 90 errno = serrno; 91 return (-1); 92 } 93 if (sb.st_dev != fsb.st_dev || 94 sb.st_ino != fsb.st_ino) { 95 /* changed under our feet */ 96 (void)close(fd); 97 continue; 98 } 99 if (trunc && ftruncate(fd, 0) != 0) { 100 /* can't happen [tm] */ 101 serrno = errno; 102 (void)close(fd); 103 errno = serrno; 104 return (-1); 105 } 106 return (fd); 107 } 108 } 109