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 
43 int
44 flock(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