45 lines
1.3 KiB
C
45 lines
1.3 KiB
C
/* $NetBSD: crc32.c,v 1.6 2003/03/29 22:25:26 thorpej Exp $ */
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/* crc32.c -- compute the CRC-32 of a data stream
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* Copyright (C) 1995-2002 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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/* @(#) $Id: crc32.c,v 1.6 2003/03/29 22:25:26 thorpej Exp $ */
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#include "zlib.h"
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#define local static
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local const uLongf crc_table[16] = {
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0x00000000L, 0x1db71064L, 0x3b6e20c8L, 0x26d930acL,
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0x76dc4190L, 0x6b6b51f4L, 0x4db26158L, 0x5005713cL,
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0xedb88320L, 0xf00f9344L, 0xd6d6a3e8L, 0xcb61b38cL,
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0x9b64c2b0L, 0x86d3d2d4L, 0xa00ae278L, 0xbdbdf21cL
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};
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/* ========================================================================= */
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#define DO1(buf) do { crc ^= *buf++; crc = (crc >> 4) ^ crc_table[crc & 0xf]; crc = (crc >> 4) ^ crc_table[crc & 0xf]; } while (0)
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#define DO2(buf) DO1(buf); DO1(buf);
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#define DO4(buf) DO2(buf); DO2(buf);
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#define DO8(buf) DO4(buf); DO4(buf);
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/* ========================================================================= */
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uLong ZEXPORT crc32(crc, buf, len)
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uLong crc;
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const Bytef *buf;
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uInt len;
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{
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if (buf == Z_NULL) return 0L;
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crc = crc ^ 0xffffffffL;
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while (len >= 8)
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{
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DO8(buf);
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len -= 8;
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}
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if (len) do {
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DO1(buf);
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} while (--len);
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return crc ^ 0xffffffffL;
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}
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