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