1/*	$NetBSD: flock.c,v 1.6 2008/04/28 20:24:12 martin Exp $	*/
2
3/*-
4 * Copyright (c) 2001 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Todd Vierling.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32/*
33 * Emulate flock() with fcntl(), where available.
34 * Otherwise, don't do locking; just pretend success.
35 */
36
37#include "includes.h"
38
39#ifndef HAVE_FLOCK
40#include <errno.h>
41#include <fcntl.h>
42
43int
44flock(int fd, int op)
45{
46	int rc = 0;
47
48#if defined(F_SETLK) && defined(F_SETLKW)
49	struct flock fl = {0};
50
51	switch (op & (LOCK_EX|LOCK_SH|LOCK_UN)) {
52	case LOCK_EX:
53		fl.l_type = F_WRLCK;
54		break;
55
56	case LOCK_SH:
57		fl.l_type = F_RDLCK;
58		break;
59
60	case LOCK_UN:
61		fl.l_type = F_UNLCK;
62		break;
63
64	default:
65		errno = EINVAL;
66		return -1;
67	}
68
69	fl.l_whence = SEEK_SET;
70	rc = fcntl(fd, op & LOCK_NB ? F_SETLK : F_SETLKW, &fl);
71
72	if (rc && (errno == EAGAIN))
73		errno = EWOULDBLOCK;
74#else
75	rc = -1;
76	errno = ENOSYS;
77#endif
78
79	return rc;
80}
81#endif
82