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flock.c

/* $Id$ */

/*
 * Copyright (c) 2001-2002 ToonTown Consulting
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the company nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"

#include <errno.h>
#include <unistd.h>

#include "flock.h"

/* There is a 0.000001% chance this errno-code might not exist. */
#ifndef EWOULDBLOCK
#define EWOULDBLOCK EAGAIN
#endif

int
flock(fd, operation)
      int fd, operation;
{
      int retval;

      /*
       * Since lockf does not have shared lock, we will in the
       * switch() fallthrough to exclusive instead.
       */
      switch (operation) {
      /* Blocking locking */
      case LOCK_SH:
            /* FALLTHROUGH */
      case LOCK_EX:
            retval = lockf(fd, F_LOCK, 0);
            break;

      /* Non-blocking locking */
      case LOCK_SH | LOCK_NB:
            /* FALLTHROUGH */
      case LOCK_EX | LOCK_NB:
            retval = lockf(fd, F_TLOCK, 0);
            break;

      /* Unlock */
      case LOCK_UN:
            retval = lockf(fd, F_ULOCK, 0);
            break;

      /* Bad operation */
      default:
            errno = EINVAL;
            retval = -1;
            break;
      }

      /* Fix errno so it's flock-compatible */
      if (retval == -1)
            switch (errno) {
            case EDEADLK:
            case ENOLCK:
                  errno = EOPNOTSUPP;
                  break;
            case EAGAIN:
                  errno = EWOULDBLOCK;
                  break;
            }

      return (retval);
}

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