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 * Derived from FreeBSD head/lib/libutil/flopen.c r193591 28 */ 29 30 #include <sys/file.h> 31 #include <sys/stat.h> 32 33 #include <errno.h> 34 #include <stdarg.h> 35 #include <unistd.h> 36 37 static int 38 flopen(const char *path, int flags, ...) 39 { 40 int fd, operation, serrno, trunc; 41 struct stat sb, fsb; 42 mode_t mode; 43 44 #ifdef O_EXLOCK 45 flags &= ~O_EXLOCK; 46 #endif 47 48 mode = 0; 49 if (flags & O_CREAT) { 50 va_list ap; 51 52 va_start(ap, flags); 53 mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */ 54 va_end(ap); 55 } 56 57 operation = LOCK_EX; 58 if (flags & O_NONBLOCK) 59 operation |= LOCK_NB; 60 61 trunc = (flags & O_TRUNC); 62 flags &= ~O_TRUNC; 63 64 for (;;) { 65 if ((fd = open(path, flags, mode)) == -1) 66 /* non-existent or no access */ 67 return (-1); 68 if (flock(fd, operation) == -1) { 69 /* unsupported or interrupted */ 70 serrno = errno; 71 (void)close(fd); 72 errno = serrno; 73 return (-1); 74 } 75 if (stat(path, &sb) == -1) { 76 /* disappeared from under our feet */ 77 (void)close(fd); 78 continue; 79 } 80 if (fstat(fd, &fsb) == -1) { 81 /* can't happen [tm] */ 82 serrno = errno; 83 (void)close(fd); 84 errno = serrno; 85 return (-1); 86 } 87 if (sb.st_dev != fsb.st_dev || 88 sb.st_ino != fsb.st_ino) { 89 /* changed under our feet */ 90 (void)close(fd); 91 continue; 92 } 93 if (trunc && ftruncate(fd, 0) != 0) { 94 /* can't happen [tm] */ 95 serrno = errno; 96 (void)close(fd); 97 errno = serrno; 98 return (-1); 99 } 100 return (fd); 101 } 102 } 103