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lfs_cksum.c revision 1.1 
      1 /*-
      2  * Copyright (c) 1991, 1993
      3  *	The Regents of the University of California.  All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. All advertising materials mentioning features or use of this software
     14  *    must display the following acknowledgement:
     15  *	This product includes software developed by the University of
     16  *	California, Berkeley and its contributors.
     17  * 4. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  *
     33  *	from: @(#)lfs_cksum.c	8.1 (Berkeley) 6/11/93
     34  *	$Id: lfs_cksum.c,v 1.1 1994/06/08 11:42:30 mycroft Exp $
     35  */
     36 
     37 #include <sys/types.h>
     38 
     39 /*
     40  * Simple, general purpose, fast checksum.  Data must be short-aligned.
     41  * Returns a u_long in case we ever want to do something more rigorous.
     42  *
     43  * XXX
     44  * Use the TCP/IP checksum instead.
     45  */
     46 u_long
     47 cksum(str, len)
     48 	register void *str;
     49 	register size_t len;
     50 {
     51 	register u_long sum;
     52 
     53 	len &= ~(sizeof(u_short) - 1);
     54 	for (sum = 0; len; len -= sizeof(u_short)) {
     55 		sum ^= *(u_short *)str;
     56 		++(u_short *)str;
     57 	}
     58 	return (sum);
     59 }
     60