1 /*-
2 * Copyright (c) 2007 Dag-Erling 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
flopen(const char * path,int flags,...)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