gen/lockf.c

   1 /*      $NetBSD: lockf.c,v 1.1 1997/12/20 20:23:18 kleink 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  * $FreeBSD: src/lib/libc/gen/lockf.c,v 1.5 2000/01/27 23:06:17 jasone Exp $
  39  */
  40
  41 #if defined(LIBC_SCCS) && !defined(lint)
  42 static const char rcsid[]=
  43   "$FreeBSD: src/lib/libc/gen/lockf.c,v 1.5 2000/01/27 23:06:17 jasone Exp $";
  44 #endif
  45
  46 #include <errno.h>
  47 #include <fcntl.h>
  48 #include <unistd.h>
  49
  50 int
  51 lockf(filedes, function, size)
  52         int filedes;
  53         int function;
  54         off_t size;
  55 {
  56         struct flock fl;
  57         int cmd;
  58
  59         fl.l_start = 0;
  60         fl.l_len = size;
  61         fl.l_whence = SEEK_CUR;
  62
  63         switch (function) {
  64         case F_ULOCK:
  65                 cmd = F_SETLK;
  66                 fl.l_type = F_UNLCK;
  67                 break;
  68         case F_LOCK:
  69                 cmd = F_SETLKW;
  70                 fl.l_type = F_WRLCK;
  71                 break;
  72         case F_TLOCK:
  73                 cmd = F_SETLK;
  74                 fl.l_type = F_WRLCK;
  75                 break;
  76         case F_TEST:
  77                 fl.l_type = F_WRLCK;
  78                 if (fcntl(filedes, F_GETLK, &fl) == -1)
  79                         return (-1);
  80                 if (fl.l_type == F_UNLCK || fl.l_pid == getpid())
  81                         return (0);
  82                 errno = EAGAIN;
  83                 return (-1);
  84                 /* NOTREACHED */
  85         default:
  86                 errno = EINVAL;
  87                 return (-1);
  88                 /* NOTREACHED */
  89         }
  90
  91         return (fcntl(filedes, cmd, &fl));
  92 }