/*
 * Copyright (c) 1998-2001 Sendmail, Inc. and its suppliers.
 *      All rights reserved.
 * Copyright (c) 1983, 1995-1997 Eric P. Allman.  All rights reserved.
 * Copyright (c) 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * By using this file, you agree to the terms and conditions set
 * forth in the LICENSE file which can be found at the top level of
 * the sendmail distribution.
 *
 */

#include <sendmail.h>

SM_RCSID("@(#)$Id: lockfile.c,v 8.21 2003/11/10 22:57:38 ca Exp $")


/*
**  LOCKFILE -- lock a file using flock or (shudder) fcntl locking
**
**      Parameters:
**              fd -- the file descriptor of the file.
**              filename -- the file name (for error messages). [unused]
**              ext -- the filename extension. [unused]
**              type -- type of the lock.  Bits can be:
**                      LOCK_EX -- exclusive lock.
**                      LOCK_NB -- non-blocking.
**                      LOCK_UN -- unlock.
**
**      Returns:
**              true if the lock was acquired.
**              false otherwise.
*/

bool
lockfile(fd, filename, ext, type)
        int fd;
        char *filename;
        char *ext;
        int type;
{
#if !HASFLOCK
        int action;
        struct flock lfd;

        memset(&lfd, '\0', sizeof lfd);
        if (bitset(LOCK_UN, type))
                lfd.l_type = F_UNLCK;
        else if (bitset(LOCK_EX, type))
                lfd.l_type = F_WRLCK;
        else
                lfd.l_type = F_RDLCK;
        if (bitset(LOCK_NB, type))
                action = F_SETLK;
        else
                action = F_SETLKW;

        if (fcntl(fd, action, &lfd) >= 0)
                return true;

        /*
        **  On SunOS, if you are testing using -oQ/tmp/mqueue or
        **  -oA/tmp/aliases or anything like that, and /tmp is mounted
        **  as type "tmp" (that is, served from swap space), the
        **  previous fcntl will fail with "Invalid argument" errors.
        **  Since this is fairly common during testing, we will assume
        **  that this indicates that the lock is successfully grabbed.
        */

        if (errno == EINVAL)
                return true;

#else /* !HASFLOCK */

        if (flock(fd, type) >= 0)
                return true;

#endif /* !HASFLOCK */

        return false;
}