flopen.c revision 169447 
1/*-
2 * Copyright (c) 2007 Dag-Erling Co�dan Sm�rgrav
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 * $Id$
28 */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD: head/lib/libutil/flopen.c 169447 2007-05-10 14:52:57Z des $");
32
33#include <sys/stat.h>
34
35#include <errno.h>
36#include <fcntl.h>
37#include <stdarg.h>
38
39int
40flopen(const char *path, int flags, ...)
41{
42	int fd, operation, serrno;
43	struct stat sb, fsb;
44	mode_t mode;
45
46#ifdef O_EXLOCK
47	flags &= ~O_EXLOCK;
48#endif
49
50	mode = 0;
51	if (flags & O_CREAT) {
52		va_list ap;
53
54		va_start(ap, flags);
55		mode = va_arg(ap, int); /* mode_t promoted to int */
56		va_end(ap);
57	}
58
59	operation = LOCK_EX;
60	if (flags & O_NONBLOCK)
61		operation |= LOCK_NB;
62
63	for (;;) {
64		if ((fd = open(path, flags, mode)) == -1)
65			/* non-existent or no access */
66			return (-1);
67		if (flock(fd, operation) == -1) {
68			/* unsupported or interrupted */
69			serrno = errno;
70			close(fd);
71			errno = serrno;
72			return (-1);
73		}
74		if (stat(path, &sb) == -1) {
75			/* disappeared from under our feet */
76			close(fd);
77			continue;
78		}
79		if (fstat(fd, &fsb) == -1) {
80			/* can't happen [tm] */
81			serrno = errno;
82			close(fd);
83			errno = serrno;
84			return (-1);
85		}
86		if (sb.st_dev != fsb.st_dev ||
87		    sb.st_ino != fsb.st_ino) {
88			/* changed under our feet */
89			close(fd);
90			continue;
91		}
92		return (fd);
93	}
94}
95