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