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 "nbtool_config.h"
38 
39 #if !HAVE_FLOCK
40 #include <errno.h>
41 #include <fcntl.h>
42 
43 int flock(int fd, int op) {
44 	int rc = 0;
45 
46 #if defined(F_SETLK) && defined(F_SETLKW)
47 	struct flock fl = {0};
48 
49 	switch (op & (LOCK_EX|LOCK_SH|LOCK_UN)) {
50 	case LOCK_EX:
51 		fl.l_type = F_WRLCK;
52 		break;
53 
54 	case LOCK_SH:
55 		fl.l_type = F_RDLCK;
56 		break;
57 
58 	case LOCK_UN:
59 		fl.l_type = F_UNLCK;
60 		break;
61 
62 	default:
63 		errno = EINVAL;
64 		return -1;
65 	}
66 
67 	fl.l_whence = SEEK_SET;
68 	rc = fcntl(fd, op & LOCK_NB ? F_SETLK : F_SETLKW, &fl);
69 
70 	if (rc && (errno == EAGAIN))
71 		errno = EWOULDBLOCK;
72 #endif
73 
74 	return rc;
75 }
76 #endif
77