unsigned long crc32_sft_buf(unsigned char * buf, unsigned long crc, unsigned long len)
{
	unsigned long i;
	unsigned char j;	
	for (i = 0; i < len; i++)
	{
		crc ^= buf[i];
		for (j = 0; j < 8; j++ )
			crc = crc & 1 ? (crc >> 1) ^ poly32 : crc >> 1;
/*
			crc = crc & 0xFFFFFFFF;
*/
	}
	return crc;
}