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chksum.c revision 1.1 
      1 /* $NetBSD: chksum.c,v 1.1 2001/12/19 06:51:05 mhitch Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 1996 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Ignatios Souvatzis.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <stdio.h>
     40 #include <unistd.h>
     41 #include <sys/types.h>
     42 
     43 #include "chksum.h"
     44 
     45 u_int32_t
     46 chksum(block, size)
     47 	u_int32_t *block;
     48 	int size;
     49 {
     50 	u_int32_t sum, lastsum;
     51 	int i;
     52 
     53 	sum = 0;
     54 
     55 	for (i=0; i<size; i++) {
     56 		lastsum = sum;
     57 		sum += htobe32(block[i]);
     58 		if (sum < lastsum)
     59 			++sum;
     60 	}
     61 
     62 	return sum;
     63 }
     64 
     65 #ifdef TESTSUM
     66 u_int32_t myblock[8192];
     67 
     68 int
     69 main(int argc, char *argb[]) {
     70 	int bbsize;
     71 	u_int32_t cks, cks1;
     72 
     73 	bbsize=atol(argb[1]);
     74 	bbsize *= (512 / sizeof (u_int32_t));
     75 
     76 	if (4*bbsize != read(0, myblock, sizeof(u_int32_t)*bbsize)) {
     77 		fprintf(stderr, "short read\n");
     78 		exit(1);
     79 	}
     80 	fprintf(stderr, "Cksum field = 0x%x, ", myblock[1]);
     81 	cks = chksum(myblock, bbsize);
     82 	fprintf(stderr, "cksum = 0x%x\n", cks);
     83 	myblock[1] += 0xFFFFFFFF - cks;
     84 	fprintf(stderr, "New cksum field = 0x%x, ", myblock[1]);
     85 	cks1 = chksum(myblock, bbsize);
     86 	fprintf(stderr, "cksum = 0x%x\n", cks1);
     87 }
     88 #endif
     89