CRC16 - IBM

http://www.codeguru.com/forum/showthread.php?referrerid=177422&t=433491

ushort ComputeCRC16(const uchar* buf, uint len)

{
 ushort crc = 0;
 for (uint j = 0; j < len; j++)
 {
  uchar b = buf[j];
  for (uchar i = 0; i < 8; i++)
  {
   crc = ((b ^ (uchar)crc) & 1) ? ((crc >> 1) ^ 0xA001) : (crc >> 1);
   b >>= 1;
  }
 }
 return crc;

}