75 lines
1.7 KiB
C
75 lines
1.7 KiB
C
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/* 7zCrc.c -- CRC32 calculation
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2009-11-23 : Igor Pavlov : Public domain */
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#include "7zCrc.h"
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#include "CpuArch.h"
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#define kCrcPoly 0xEDB88320
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#ifdef MY_CPU_LE
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#define CRC_NUM_TABLES 8
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#else
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#define CRC_NUM_TABLES 1
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#endif
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typedef UInt32 (MY_FAST_CALL *CRC_FUNC)(UInt32 v, const void *data, size_t size, const UInt32 *table);
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static CRC_FUNC g_CrcUpdate;
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UInt32 g_CrcTable[256 * CRC_NUM_TABLES];
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#if CRC_NUM_TABLES == 1
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#define CRC_UPDATE_BYTE_2(crc, b) (table[((crc) ^ (b)) & 0xFF] ^ ((crc) >> 8))
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static UInt32 MY_FAST_CALL CrcUpdateT1(UInt32 v, const void *data, size_t size, const UInt32 *table)
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{
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const Byte *p = (const Byte *)data;
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for (; size > 0; size--, p++)
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v = CRC_UPDATE_BYTE_2(v, *p);
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return v;
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}
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#else
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UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
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UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void *data, size_t size, const UInt32 *table);
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#endif
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UInt32 MY_FAST_CALL CrcUpdate(UInt32 v, const void *data, size_t size)
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{
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return g_CrcUpdate(v, data, size, g_CrcTable);
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}
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UInt32 MY_FAST_CALL CrcCalc(const void *data, size_t size)
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{
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return g_CrcUpdate(CRC_INIT_VAL, data, size, g_CrcTable) ^ CRC_INIT_VAL;
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}
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void MY_FAST_CALL CrcGenerateTable()
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{
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UInt32 i;
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for (i = 0; i < 256; i++)
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{
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UInt32 r = i;
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unsigned j;
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for (j = 0; j < 8; j++)
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r = (r >> 1) ^ (kCrcPoly & ~((r & 1) - 1));
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g_CrcTable[i] = r;
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}
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#if CRC_NUM_TABLES == 1
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g_CrcUpdate = CrcUpdateT1;
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#else
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for (; i < 256 * CRC_NUM_TABLES; i++)
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{
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UInt32 r = g_CrcTable[i - 256];
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g_CrcTable[i] = g_CrcTable[r & 0xFF] ^ (r >> 8);
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}
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g_CrcUpdate = CrcUpdateT4;
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#ifdef MY_CPU_X86_OR_AMD64
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if (!CPU_Is_InOrder())
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g_CrcUpdate = CrcUpdateT8;
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#endif
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#endif
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}
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