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lockf.c revision 1.3.8.2 
      1 /*	$NetBSD: lockf.c,v 1.3.8.2 2008/04/28 20:23:00 martin 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 1.3.8.2 2008/04/28 20:23:00 martin 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
     43 __weak_alias(lockf,_lockf)
     44 #endif
     45 
     46 
     47 int
     48 lockf(filedes, function, size)
     49 	int filedes;
     50 	int function;
     51 	off_t size;
     52 {
     53 	struct flock fl;
     54 	int cmd;
     55 
     56 	fl.l_start = 0;
     57 	fl.l_len = size;
     58 	fl.l_whence = SEEK_CUR;
     59 
     60 	switch (function) {
     61 	case F_ULOCK:
     62 		cmd = F_SETLK;
     63 		fl.l_type = F_UNLCK;
     64 		break;
     65 	case F_LOCK:
     66 		cmd = F_SETLKW;
     67 		fl.l_type = F_WRLCK;
     68 		break;
     69 	case F_TLOCK:
     70 		cmd = F_SETLK;
     71 		fl.l_type = F_WRLCK;
     72 		break;
     73 	case F_TEST:
     74 		fl.l_type = F_WRLCK;
     75 		if (fcntl(filedes, F_GETLK, &fl) == -1)
     76 			return (-1);
     77 		if (fl.l_type == F_UNLCK || fl.l_pid == getpid())
     78 			return (0);
     79 		errno = EAGAIN;
     80 		return (-1);
     81 		/* NOTREACHED */
     82 	default:
     83 		errno = EINVAL;
     84 		return (-1);
     85 		/* NOTREACHED */
     86 	}
     87 
     88 	return (fcntl(filedes, cmd, &fl));
     89 }
     90