xref: /minix3/lib/libc/gen/lockf.c (revision f14fb602092e015ff630df58e17c2a9cd57d29b3)
1 /*	$NetBSD: lockf.c,v 1.4 2012/06/25 22:32:43 abs Exp $	*/
2 
3 /*-
4  * Copyright (c) 1997 The NetBSD Foundation, Inc.
5  * All rights reserved.
6  *
7  * This code is derived from software contributed to The NetBSD Foundation
8  * by Klaus Klein.
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 #include <sys/cdefs.h>
33 #if defined(LIBC_SCCS) && !defined(lint)
34 __RCSID("$NetBSD: lockf.c,v 1.4 2012/06/25 22:32:43 abs Exp $");
35 #endif
36 
37 #include "namespace.h"
38 #include <errno.h>
39 #include <fcntl.h>
40 #include <unistd.h>
41 
42 #ifdef __weak_alias
__weak_alias(lockf,_lockf)43 __weak_alias(lockf,_lockf)
44 #endif
45 
46 
47 int
48 lockf(int filedes, int function, off_t size)
49 {
50 	struct flock fl;
51 	int cmd;
52 
53 	fl.l_start = 0;
54 	fl.l_len = size;
55 	fl.l_whence = SEEK_CUR;
56 
57 	switch (function) {
58 	case F_ULOCK:
59 		cmd = F_SETLK;
60 		fl.l_type = F_UNLCK;
61 		break;
62 	case F_LOCK:
63 		cmd = F_SETLKW;
64 		fl.l_type = F_WRLCK;
65 		break;
66 	case F_TLOCK:
67 		cmd = F_SETLK;
68 		fl.l_type = F_WRLCK;
69 		break;
70 	case F_TEST:
71 		fl.l_type = F_WRLCK;
72 		if (fcntl(filedes, F_GETLK, &fl) == -1)
73 			return (-1);
74 		if (fl.l_type == F_UNLCK || fl.l_pid == getpid())
75 			return (0);
76 		errno = EAGAIN;
77 		return (-1);
78 		/* NOTREACHED */
79 	default:
80 		errno = EINVAL;
81 		return (-1);
82 		/* NOTREACHED */
83 	}
84 
85 	return (fcntl(filedes, cmd, &fl));
86 }
87