138 lines
6.8 KiB
C
138 lines
6.8 KiB
C
/*****************************************************************************
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*
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* $Id: crc.c,v 1.4 2005/12/17 16:35:10 mbse Exp $
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* Purpose ...............: Crc32 calculations
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*
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*****************************************************************************
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* Copyright (C) 1993-2005
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*
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* Michiel Broek FIDO: 2:280/2802
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* Beekmansbos 10
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* 1971 BV IJmuiden
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* the Netherlands
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*
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* This file is part of MBSE BBS
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*
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* This BBS is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2, or (at your option) any
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* later version.
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*
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* MB BBS is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with MB BBS; see the file COPYING. If not, write to the Free
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* Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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*****************************************************************************/
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#include "../config.h"
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#include "../lib/mbselib.h"
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/*
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* Copyright (C) 1986 Gary S. Brown. You may use this program, or
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* code or tables extracted from it, as desired without restriction.
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*/
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/* First, the polynomial itself and its table of feedback terms. The */
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/* polynomial is */
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/* X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0 */
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/* Note that we take it "backwards" and put the highest-order term in */
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/* the lowest-order bit. The X^32 term is "implied"; the LSB is the */
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/* X^31 term, etc. The X^0 term (usually shown as "+1") results in */
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/* the MSB being 1. */
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/* Note that the usual hardware shift register implementation, which */
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/* is what we're using (we're merely optimizing it by doing eight-bit */
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/* chunks at a time) shifts bits into the lowest-order term. In our */
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/* implementation, that means shifting towards the right. Why do we */
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/* do it this way? Because the calculated CRC must be transmitted in */
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/* order from highest-order term to lowest-order term. UARTs transmit */
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/* characters in order from LSB to MSB. By storing the CRC this way, */
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/* we hand it to the UART in the order low-byte to high-byte; the UART */
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/* sends each low-bit to hight-bit; and the result is transmission bit */
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/* by bit from highest- to lowest-order term without requiring any bit */
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/* shuffling on our part. Reception works similarly. */
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/* The feedback terms table consists of 256, 32-bit entries. Notes: */
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/* */
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/* The table can be generated at runtime if desired; code to do so */
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/* is shown later. It might not be obvious, but the feedback */
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/* terms simply represent the results of eight shift/xor opera- */
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/* tions for all combinations of data and CRC register values. */
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/* */
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/* The values must be right-shifted by eight bits by the "updcrc" */
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/* logic; the shift must be unsigned (bring in zeroes). On some */
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/* hardware you could probably optimize the shift in assembler by */
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/* using byte-swap instructions. */
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unsigned int crc32tab[] = { /* CRC polynomial 0xedb88320 */
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0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
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0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
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0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
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0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
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0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
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0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
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0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
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0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
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0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
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0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
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0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
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0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
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0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
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0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
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0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
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0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
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0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
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0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
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0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
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0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
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0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
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0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
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0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
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0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
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0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
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0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
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0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
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0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
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0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
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0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
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0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
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0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
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};
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unsigned int StringCRC32(char *str)
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{
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unsigned int crc;
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for (crc = 0xffffffff; *str; str++)
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crc = crc32tab[((int)crc^(*str)) & 0xff] ^ ((crc>>8) & 0x00ffffff);
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return crc;
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}
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/*
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* Update CRC32, first initialize crc with 0xffffffff
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*/
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unsigned int upd_crc32(char *buf, unsigned int crc, int len)
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{
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int i;
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unsigned int cr;
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cr = crc;
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for (i = 0; i < len; i++) {
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cr = (crc32tab[((int)cr ^ ((int)buf[i])) & 0xff] ^ ((((unsigned int)cr) >> 8) & 0x00ffffffL));
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}
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return cr;
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}
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