1 /* $NetBSD: flock.c,v 1.4 2002/06/07 21:13:55 mason 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 * 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 /* 40 * Emulate flock() with fcntl(), where available. 41 * Otherwise, don't do locking; just pretend success. 42 */ 43 44 #include "config.h" 45 46 #if !HAVE_FLOCK 47 #include <errno.h> 48 #include <fcntl.h> 49 50 int flock(int fd, int op) { 51 int rc = 0; 52 53 #if defined(F_SETLK) && defined(F_SETLKW) 54 struct flock fl = {0}; 55 56 switch (op & (LOCK_EX|LOCK_SH|LOCK_UN)) { 57 case LOCK_EX: 58 fl.l_type = F_WRLCK; 59 break; 60 61 case LOCK_SH: 62 fl.l_type = F_RDLCK; 63 break; 64 65 case LOCK_UN: 66 fl.l_type = F_UNLCK; 67 break; 68 69 default: 70 errno = EINVAL; 71 return -1; 72 } 73 74 fl.l_whence = SEEK_SET; 75 rc = fcntl(fd, op & LOCK_NB ? F_SETLK : F_SETLKW, &fl); 76 77 if (rc && (errno == EAGAIN)) 78 errno = EWOULDBLOCK; 79 #endif 80 81 return rc; 82 } 83 #endif 84