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44 lines
744 B
C
44 lines
744 B
C
// Copyright 2022 Dietrich Epp.
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// This file is part of SyncFiles. SyncFiles is licensed under the terms of the
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// Mozilla Public License, version 2.0. See LICENSE.txt for details.
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#include "lib/crc32.h"
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static int gCRCInitted;
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static UInt32 gCRCTable[256];
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static void CRC32Init(void)
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{
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int i, j;
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UInt32 v, u;
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for (i = 0; i < 256; i++) {
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v = i;
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for (j = 0; j < 8; j++) {
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u = v;
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v >>= 1;
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if (u & 1) {
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v ^= 0xedb88320;
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}
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}
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gCRCTable[i] = v;
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}
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gCRCInitted = 1;
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}
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UInt32 CRC32Update(UInt32 crc, const void *ptr, Size size)
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{
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const UInt8 *p, *e;
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if (!gCRCInitted) {
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CRC32Init();
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}
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crc = ~crc;
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p = ptr;
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e = p + size;
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while (p < e) {
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crc = (crc >> 8) ^ gCRCTable[(crc & 0xff) ^ *p++];
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}
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return ~crc;
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}
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