flopen.h revision 293161 
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 * 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
37static int
38flopen(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