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      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