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: head/lib/libutil/flopen.c 193591 2009-06-06 18:47:03Z des $
28 */
29
30 #include <sys/stat.h>
31
32 #include <errno.h>
33 #include <stdarg.h>
34 #include <unistd.h>
35 #include <fcntl.h>
36 #include <libutil.h>
37
38 int
flopen(const char * path,int flags,...)39 flopen(const char *path, int flags, ...)
40 {
41 int fd, operation, serrno, trunc;
42 struct stat sb, fsb;
43 mode_t mode;
44
45 #ifdef O_EXLOCK
46 flags &= ~O_EXLOCK;
47 #endif
48
49 mode = 0;
50 if (flags & O_CREAT) {
51 va_list ap;
52
53 va_start(ap, flags);
54 mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */
55 va_end(ap);
56 }
57
58 operation = LOCK_EX;
59 if (flags & O_NONBLOCK)
60 operation |= LOCK_NB;
61
62 trunc = (flags & O_TRUNC);
63 flags &= ~O_TRUNC;
64
65 for (;;) {
66 if ((fd = open(path, flags, mode)) == -1)
67 /* non-existent or no access */
68 return (-1);
69 if (flock(fd, operation) == -1) {
70 /* unsupported or interrupted */
71 serrno = errno;
72 (void)close(fd);
73 errno = serrno;
74 return (-1);
75 }
76 if (stat(path, &sb) == -1) {
77 /* disappeared from under our feet */
78 (void)close(fd);
79 continue;
80 }
81 if (fstat(fd, &fsb) == -1) {
82 /* can't happen [tm] */
83 serrno = errno;
84 (void)close(fd);
85 errno = serrno;
86 return (-1);
87 }
88 if (sb.st_dev != fsb.st_dev ||
89 sb.st_ino != fsb.st_ino) {
90 /* changed under our feet */
91 (void)close(fd);
92 continue;
93 }
94 if (trunc && ftruncate(fd, 0) != 0) {
95 /* can't happen [tm] */
96 serrno = errno;
97 (void)close(fd);
98 errno = serrno;
99 return (-1);
100 }
101 return (fd);
102 }
103 }
104