| 7 | # SPDX-License-Identifier: BSD-3-Clause |
| 8 | |
| 9 | class Crc16(object): |
| 10 | POLY = 0x1021 |
| 11 | |
| 12 | def __init__(self, crcStart=0xEF4A): |
| 13 | self._crcStart = crcStart |
| 14 | self._table = [self.compute_table(i) for i in range(256)] |
| 15 | |
| 16 | def compute_table(self, i): |
| 17 | crc = 0 |
| 18 | i <<= 8 |
| 19 | for b in range(8): |
| 20 | temp = crc ^ i |
| 21 | crc <<= 1 |
| 22 | if temp & 0x8000: |
| 23 | crc ^= self.POLY |
| 24 | i <<= 1 |
| 25 | return crc |
| 26 | |
| 27 | def computeCRC16(self, data): |
| 28 | if isinstance(data, str): |
| 29 | data = bytearray(data) |
| 30 | crc = self._crcStart |
| 31 | for c in data: |
| 32 | crc = ((crc << 8) ^ self._table[((crc >> 8) ^ c) & 0xff]) & 0xffff |
| 33 | return crc |