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