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/* 7zCrc.c -- CRC32 init
2010-12-01 : Igor Pavlov : Public domain */

#include "7zCrc.h"
#include "CpuArch.h"

#define kCrcPoly 0xEDB88320

#if defined(MY_CPU_LE)
	#define CRC_NUM_TABLES 4
#else
	#define CRC_NUM_TABLES 5
	#define CRC_UINT32_SWAP(v) ((v >> 24) | ((v >> 8) & 0xFF00) | ((v << 8) & 0xFF0000) | (v << 24))
	UInt32 MY_FAST_CALL CrcUpdateT1_BeT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
#endif

#ifndef MY_CPU_BE
	UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
#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];

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;
	}
	for (; i < 256 * CRC_NUM_TABLES; i++)
	{
	UInt32 r = g_CrcTable[i - 256];
	g_CrcTable[i] = g_CrcTable[r & 0xFF] ^ (r >> 8);
	}

	#ifdef MY_CPU_LE

	g_CrcUpdate = CrcUpdateT4;

	#if CRC_NUM_TABLES == 8
	if (!CPU_Is_InOrder())
	g_CrcUpdate = CrcUpdateT8;
	#endif

	#else
	{
	#ifndef MY_CPU_BE
	UInt32 k = 1;
	if (*(const Byte *)&k == 1)
		g_CrcUpdate = CrcUpdateT4;
	else
	#endif
	{
		for (i = 256 * CRC_NUM_TABLES - 1; i >= 256; i--)
		{
		UInt32 x = g_CrcTable[i - 256];
		g_CrcTable[i] = CRC_UINT32_SWAP(x);
		}
		g_CrcUpdate = CrcUpdateT1_BeT4;
	}
	}
	#endif
}