flopen.c revision 169899 
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
28#include <sys/cdefs.h>
29__FBSDID("$FreeBSD: head/lib/libutil/flopen.c 169899 2007-05-23 12:09:33Z des $");
30
31#include <sys/file.h>
32#include <sys/stat.h>
33
34#include <errno.h>
35#include <fcntl.h>
36#include <stdarg.h>
37#include <unistd.h>
38
39#include <libutil.h>
40
41int
42flopen(const char *path, int flags, ...)
43{
44	int fd, operation, serrno, trunc;
45	struct stat sb, fsb;
46	mode_t mode;
47
48#ifdef O_EXLOCK
49	flags &= ~O_EXLOCK;
50#endif
51
52	mode = 0;
53	if (flags & O_CREAT) {
54		va_list ap;
55
56		va_start(ap, flags);
57		mode = va_arg(ap, int); /* mode_t promoted to int */
58		va_end(ap);
59	}
60
61	operation = LOCK_EX;
62	if (flags & O_NONBLOCK)
63		operation |= LOCK_NB;
64
65	trunc = (flags & O_TRUNC);
66	flags &= ~O_TRUNC;
67
68	for (;;) {
69		if ((fd = open(path, flags, mode)) == -1)
70			/* non-existent or no access */
71			return (-1);
72		if (flock(fd, operation) == -1) {
73			/* unsupported or interrupted */
74			serrno = errno;
75			close(fd);
76			errno = serrno;
77			return (-1);
78		}
79		if (stat(path, &sb) == -1) {
80			/* disappeared from under our feet */
81			close(fd);
82			continue;
83		}
84		if (fstat(fd, &fsb) == -1) {
85			/* can't happen [tm] */
86			serrno = errno;
87			close(fd);
88			errno = serrno;
89			return (-1);
90		}
91		if (sb.st_dev != fsb.st_dev ||
92		    sb.st_ino != fsb.st_ino) {
93			/* changed under our feet */
94			close(fd);
95			continue;
96		}
97		if (trunc && ftruncate(fd, 0) != 0) {
98			/* can't happen [tm] */
99			serrno = errno;
100			close(fd);
101			errno = serrno;
102			return (-1);
103		}
104		return (fd);
105	}
106}
107