#include "stdafx.h"
#include "CRC.h"

#define POLY64REV     0x95AC9329AC4BC9B5ULL
#define INITIALCRC    0xFFFFFFFFFFFFFFFFULL  

unsigned long long CRC64::CRCTable[256] = { 0 };

CRC64::CRC64()
{
	int i, j;
	unsigned long long part;
	for (i = 0; i < 256; i++)
	{
		part = i;
		for (j = 0; j < 8; j++)
		{
			if (part & 1)
				part = (part >> 1) ^ POLY64REV;
			else
				part >>= 1;
		}
		CRCTable[i] = part;
	}
}

UINT64 CRC64::GetCrc64(const char* pSrc, DWORD size)
{
	unsigned long long crc = INITIALCRC;
	for (DWORD i = 0; i < size; i++)
	{
		crc = CRCTable[(crc ^ pSrc[i]) & 0xff] ^ (crc >> 8);
	}

	return crc;
}