Created
October 28, 2014 10:48
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Non-table based implementations of crc16 and crc8-maxim
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| import crcmod.predefined | |
| def _crc16(crc, c): | |
| crc ^= ord(c) | |
| for i in range(8): | |
| if crc & 0x1: | |
| crc = (crc >> 1) ^ 0xA001 | |
| else: | |
| crc = (crc >> 1) | |
| return crc | |
| def crc16(s): | |
| crc = 0 | |
| for c in s: | |
| crc = _crc16(crc,c) | |
| return crc | |
| def _crc8maxim(crc, c): | |
| crc ^= ord(c) | |
| for i in range(8): | |
| if crc & 0x1: | |
| crc = (crc >> 1) ^ 0x8C | |
| else: | |
| crc = (crc >> 1) | |
| return crc | |
| def crc8maxim(s): | |
| crc = 0 | |
| for c in s: | |
| crc = _crc8maxim(crc,c) | |
| return crc | |
| if __name__ == "__main__": | |
| S = 'test124' | |
| print "CRC16 (%s)" % S | |
| crc = crcmod.predefined.Crc('crc-16') | |
| crc.update(S) | |
| print hex(crc.crcValue), 'vs', hex(crc16(S)) | |
| print "CRC8 (%s)" % S | |
| crc = crcmod.predefined.Crc('crc-8-maxim') | |
| crc.update(S) | |
| print hex(crc.crcValue), 'vs', hex(crc8maxim(S)) | |
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