1 /* 7zCrc.c -- CRC32 calculation
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2 2009-11-23 : Igor Pavlov : Public domain */
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7 #define kCrcPoly 0xEDB88320
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10 #define CRC_NUM_TABLES 8
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12 #define CRC_NUM_TABLES 1
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15 typedef UInt32 (MY_FAST_CALL *CRC_FUNC)(UInt32 v, const void *data, size_t size, const UInt32 *table);
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17 static CRC_FUNC g_CrcUpdate;
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18 UInt32 g_CrcTable[256 * CRC_NUM_TABLES];
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20 #if CRC_NUM_TABLES == 1
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22 #define CRC_UPDATE_BYTE_2(crc, b) (table[((crc) ^ (b)) & 0xFF] ^ ((crc) >> 8))
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24 static UInt32 MY_FAST_CALL CrcUpdateT1(UInt32 v, const void *data, size_t size, const UInt32 *table)
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26 const Byte *p = (const Byte *)data;
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27 for (; size > 0; size--, p++)
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28 v = CRC_UPDATE_BYTE_2(v, *p);
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34 UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
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35 UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void *data, size_t size, const UInt32 *table);
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39 UInt32 MY_FAST_CALL CrcUpdate(UInt32 v, const void *data, size_t size)
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41 return g_CrcUpdate(v, data, size, g_CrcTable);
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44 UInt32 MY_FAST_CALL CrcCalc(const void *data, size_t size)
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46 return g_CrcUpdate(CRC_INIT_VAL, data, size, g_CrcTable) ^ CRC_INIT_VAL;
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49 void MY_FAST_CALL CrcGenerateTable()
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52 for (i = 0; i < 256; i++)
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56 for (j = 0; j < 8; j++)
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57 r = (r >> 1) ^ (kCrcPoly & ~((r & 1) - 1));
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60 #if CRC_NUM_TABLES == 1
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61 g_CrcUpdate = CrcUpdateT1;
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63 for (; i < 256 * CRC_NUM_TABLES; i++)
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65 UInt32 r = g_CrcTable[i - 256];
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66 g_CrcTable[i] = g_CrcTable[r & 0xFF] ^ (r >> 8);
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68 g_CrcUpdate = CrcUpdateT4;
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69 #ifdef MY_CPU_X86_OR_AMD64
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70 if (!CPU_Is_InOrder())
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71 g_CrcUpdate = CrcUpdateT8;
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