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100 lines
2.9 KiB
100 lines
2.9 KiB
/* $Id: crc32.c,v 1.2 2006/09/09 10:15:07 pefo Exp $ */
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/*
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* Copyright (c) 1983 Regents of the University of California.
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* All rights reserved.
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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. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* CRC32 support functions.
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*/
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#include <sys/types.h>
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#include <crc32.h>
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/*
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* CRC generator shortcut table.
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*/
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static const u_int crctab[] = {
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0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
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0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
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0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
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0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c
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};
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/*
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* Generate CRC32 for data block 'data' with size 'length'.
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*
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* Returns generated CRC32.
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*/
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u_int
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crc32_generate(void *data, size_t length)
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{
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return crc32_generate_seg(data, length, 0xffffffff);
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}
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u_int
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crc32_generate_seg(void *data, size_t length, u_int crc)
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{
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const u_char *p = data;
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const u_int *crctabp = crctab;
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int i;
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if (length < 1)
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return -1;
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i = length;
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while (i-- > 0) {
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crc ^= *p++;
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crc = (crc >> 4) ^ crctabp[crc & 0xf];
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crc = (crc >> 4) ^ crctabp[crc & 0xf];
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}
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return crc;
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}
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/*
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* Check CRC32 for data block 'data' with size 'length'.
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* Last two bytes is the CRC32.
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*
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* Returns -1 if data out of range.
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* Returns 0 if CRC32 is checked OK.
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* Returns > 0 if CRC32 is checked BAD.
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*/
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u_int
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crc32_check(void *data, size_t length)
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{
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const u_char *p = data;
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int result;
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if (length < 5)
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return -1;
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result = crc32_generate(data, length - 4);
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p += length - 4;
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result ^= p[0] | p[1] << 8 | p[2] << 16 | p[3] << 24;
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return result;
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}
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