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chksum.c revision 1.6 
      1 /* $NetBSD: chksum.c,v 1.6 2022/04/25 13:43:50 rin 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  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #if HAVE_NBTOOL_CONFIG_H
     33 #include "nbtool_config.h"
     34 #endif
     35 
     36 #include <stdio.h>
     37 #include <unistd.h>
     38 #include <sys/types.h>
     39 
     40 #include "chksum.h"
     41 
     42 uint32_t
     43 chksum(uint32_t *block, int size)
     44 {
     45 	uint32_t sum, lastsum;
     46 	int i;
     47 
     48 	sum = 0;
     49 
     50 	for (i=0; i<size; i++) {
     51 		lastsum = sum;
     52 		sum += htobe32(block[i]);
     53 		if (sum < lastsum)
     54 			++sum;
     55 	}
     56 
     57 	return sum;
     58 }
     59 
     60 #ifdef TESTSUM
     61 uint32_t myblock[8192];
     62 
     63 int
     64 main(int argc, char *argb[]) {
     65 	int bbsize;
     66 	uint32_t cks, cks1;
     67 
     68 	bbsize=atol(argb[1]);
     69 	bbsize *= (512 / sizeof (uint32_t));
     70 
     71 	if (4*bbsize != read(0, myblock, sizeof(uint32_t)*bbsize)) {
     72 		fprintf(stderr, "short read\n");
     73 		exit(1);
     74 	}
     75 	fprintf(stderr, "Cksum field = 0x%x, ", myblock[1]);
     76 	cks = chksum(myblock, bbsize);
     77 	fprintf(stderr, "cksum = 0x%x\n", cks);
     78 	myblock[1] += 0xFFFFFFFF - cks;
     79 	fprintf(stderr, "New cksum field = 0x%x, ", myblock[1]);
     80 	cks1 = chksum(myblock, bbsize);
     81 	fprintf(stderr, "cksum = 0x%x\n", cks1);
     82 }
     83 #endif
     84