tools/compat/flock.c

   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