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lfs_cksum.c revision 1.7 
      1 /*	$NetBSD: lfs_cksum.c,v 1.7 1997/09/15 06:44:48 lukem Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1991, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  *
     35  *	@(#)lfs_cksum.c	8.2 (Berkeley) 10/9/94
     36  */
     37 
     38 #include <sys/types.h>
     39 #ifdef _KERNEL
     40 #include <ufs/lfs/lfs_extern.h>
     41 #else
     42 u_long cksum __P((void *, size_t));
     43 #endif
     44 
     45 /*
     46  * Simple, general purpose, fast checksum.  Data must be short-aligned.
     47  * Returns a u_long in case we ever want to do something more rigorous.
     48  *
     49  * XXX
     50  * Use the TCP/IP checksum instead.
     51  */
     52 u_long
     53 cksum(str, len)
     54 	register void *str;
     55 	register size_t len;
     56 {
     57 	register u_long sum;
     58 
     59 	len &= ~(sizeof(u_short) - 1);
     60 	for (sum = 0; len; len -= sizeof(u_short)) {
     61 		sum ^= *(u_short *)str;
     62 		str = (void *)((u_short *)str + 1);
     63 	}
     64 	return (sum);
     65 }
     66