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lockf.c revision 1.2 
      1 /*	$NetBSD: lockf.c,v 1.2 2000/01/22 22:19:11 mycroft 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  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 __RCSID("$NetBSD: lockf.c,v 1.2 2000/01/22 22:19:11 mycroft Exp $");
     42 #endif
     43 
     44 #include "namespace.h"
     45 #include <errno.h>
     46 #include <fcntl.h>
     47 #include <unistd.h>
     48 
     49 #ifdef __weak_alias
     50 __weak_alias(lockf,_lockf)
     51 #endif
     52 
     53 
     54 int
     55 lockf(filedes, function, size)
     56 	int filedes;
     57 	int function;
     58 	off_t size;
     59 {
     60 	struct flock fl;
     61 	int cmd;
     62 
     63 	fl.l_start = 0;
     64 	fl.l_len = size;
     65 	fl.l_whence = SEEK_CUR;
     66 
     67 	switch (function) {
     68 	case F_ULOCK:
     69 		cmd = F_SETLK;
     70 		fl.l_type = F_UNLCK;
     71 		break;
     72 	case F_LOCK:
     73 		cmd = F_SETLKW;
     74 		fl.l_type = F_WRLCK;
     75 		break;
     76 	case F_TLOCK:
     77 		cmd = F_SETLK;
     78 		fl.l_type = F_WRLCK;
     79 		break;
     80 	case F_TEST:
     81 		fl.l_type = F_WRLCK;
     82 		if (fcntl(filedes, F_GETLK, &fl) == -1)
     83 			return (-1);
     84 		if (fl.l_type == F_UNLCK || fl.l_pid == getpid())
     85 			return (0);
     86 		errno = EAGAIN;
     87 		return (-1);
     88 		/* NOTREACHED */
     89 	default:
     90 		errno = EINVAL;
     91 		return (-1);
     92 		/* NOTREACHED */
     93 	}
     94 
     95 	return (fcntl(filedes, cmd, &fl));
     96 }
     97