89 lines
2.8 KiB
C
89 lines
2.8 KiB
C
/* $NetBSD: chksum.c,v 1.3 1999/02/16 23:34:10 is Exp $ */
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/*-
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* Copyright (c) 1996 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Ignatios Souvatzis.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include "chksum.h"
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u_int32_t
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chksum(block, size)
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u_int32_t *block;
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int size;
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{
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u_int32_t sum, lastsum;
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int i;
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sum = 0;
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for (i=0; i<size; i++) {
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lastsum = sum;
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sum += block[i];
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if (sum < lastsum)
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++sum;
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}
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return sum;
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}
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#ifdef TESTSUM
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u_int32_t myblock[8192];
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int
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main(int argc, char *argb[]) {
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int bbsize;
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u_int32_t cks, cks1;
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bbsize=atol(argb[1]);
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bbsize *= (512 / sizeof (u_int32_t));
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if (4*bbsize != read(0, myblock, sizeof(u_int32_t)*bbsize)) {
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fprintf(stderr, "short read\n");
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exit(1);
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}
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fprintf(stderr, "Cksum field = 0x%x, ", myblock[1]);
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cks = chksum(myblock, bbsize);
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fprintf(stderr, "cksum = 0x%x\n", cks);
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myblock[1] += 0xFFFFFFFF - cks;
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fprintf(stderr, "New cksum field = 0x%x, ", myblock[1]);
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cks1 = chksum(myblock, bbsize);
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fprintf(stderr, "cksum = 0x%x\n", cks1);
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}
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#endif
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