Or in pseudo code:
<pre>
# x^16 is not explicitly stored in the magic number 0x1021, it's implicit in CRC-16 calculationsCRC_POLY = 0x1021
def crc16_ccitt(crc, byte):
crc ^= (byte << 8)
for _ in range(8):
if crc & 0x8000:
crc = (crc << 1) ^ CRC_POLY0x1021
else:
crc = crc << 1