flock.c

unix/linux下的路由守护程序

/*
 * Public Release 3
 * 
 * $Id: flock.c,v 1.5 1999/03/21 09:05:41 naamato Exp $
 */

/*
 * ------------------------------------------------------------------------
 * 
 * Copyright (c) 1996, 1997 The Regents of the University of Michigan
 * All Rights Reserved
 *  
 * Royalty-free licenses to redistribute GateD Release
 * 3 in whole or in part may be obtained by writing to:
 * 
 * 	Merit GateDaemon Project
 * 	4251 Plymouth Road, Suite C
 * 	Ann Arbor, MI 48105
 *  
 * THIS SOFTWARE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION WARRANTIES OF 
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE REGENTS OF THE
 * UNIVERSITY OF MICHIGAN AND MERIT DO NOT WARRANT THAT THE
 * FUNCTIONS CONTAINED IN THE SOFTWARE WILL MEET LICENSEE'S REQUIREMENTS OR
 * THAT OPERATION WILL BE UNINTERRUPTED OR ERROR FREE. The Regents of the
 * University of Michigan and Merit shall not be liable for
 * any special, indirect, incidental or consequential damages with respect
 * to any claim by Licensee or any third party arising from use of the
 * software. GateDaemon was originated and developed through release 3.0
 * by Cornell University and its collaborators.
 * 
 * Please forward bug fixes, enhancements and questions to the
 * gated mailing list: [e-mail].
 * 
 * ------------------------------------------------------------------------
 * 
 * Copyright (c) 1990,1991,1992,1993,1994,1995 by Cornell University.
 *     All rights reserved.
 * 
 * THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
 * LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.
 * 
 * GateD is based on Kirton's EGP, UC Berkeley's routing
 * daemon	 (routed), and DCN's HELLO routing Protocol.
 * Development of GateD has been supported in part by the
 * National Science Foundation.
 * 
 * ------------------------------------------------------------------------
 * 
 * Portions of this software may fall under the following
 * copyrights:
 * 
 * Copyright (c) 1988 Regents of the University of California.
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms are
 * permitted provided that the above copyright notice and
 * this paragraph are duplicated in all such forms and that
 * any documentation, advertising materials, and other
 * materials related to such distribution and use
 * acknowledge that the software was developed by the
 * University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote
 * products derived from this software without specific
 * prior written permission.  THIS SOFTWARE IS PROVIDED
 * ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#define	INCLUDE_FILE
#define	INCLUDE_STAT

#include "include.h"

/* Emulation of flock() using lockf() */

#if	__GNUC__ >= 2
PROTOTYPE(flock,
	  int,
	  (int,
	   int));
#endif	/* __GNUC__ >= 2 */
int
flock(fd, flags)
int fd;
int flags;
{
#ifdef	F_LOCK
    int rc;
    int cmd = 0;

    switch (BIT_TEST(flags, LOCK_EX|LOCK_SH|LOCK_UN)) {

    case LOCK_SH|LOCK_EX:
    case LOCK_EX:
	cmd = BIT_TEST(flags, LOCK_NB) ? F_TLOCK : F_LOCK;

	break;

    case LOCK_UN:
	cmd = F_ULOCK;
	break;

    case LOCK_SH:
	/* We don`t do shared locks */
    default:
	errno = EINVAL;
	return -1;
    }
    
    lseek(fd, 0L, 0);

    NON_INTR(rc, lockf(fd, cmd, 0L));
    if (rc < 0) {
	switch (errno) {
	case EACCES:
	case EAGAIN:
	    errno = EWOULDBLOCK;
	    break;

	default:
	    break;
	}
    }

    return rc;
#else	/* F_LOCK */
cannot compile
#endif	/* F_LOCK */
}