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Encapsulate crc16() to avoid global (#566)

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This commit is contained in:
Felipe Martins Diel 2021-04-01 15:02:35 -03:00 committed by Felipe Martins Diel
parent 86b5d0727c
commit 4e1e690762
2 changed files with 35 additions and 29 deletions
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6
broadlink/climate.py
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@ -3,7 +3,7 @@ from typing import List
from . import exceptions as e from . import exceptions as e
from .device import device from .device import device
from .helpers import crc16 from .helpers import CRC16
class hysen(device): class hysen(device):
@ -19,7 +19,7 @@ class hysen(device):
def send_request(self, input_payload: bytes) -> bytes: def send_request(self, input_payload: bytes) -> bytes:
"""Send a request to the device.""" """Send a request to the device."""
crc = crc16(input_payload) crc = CRC16.calculate(input_payload)
# first byte is length, +2 for CRC16 # first byte is length, +2 for CRC16
request_payload = bytearray([len(input_payload) + 2, 0x00]) request_payload = bytearray([len(input_payload) + 2, 0x00])
@ -40,7 +40,7 @@ class hysen(device):
raise ValueError( raise ValueError(
"hysen_response_error", "first byte of response is not length" "hysen_response_error", "first byte of response is not length"
) )
crc = crc16(response_payload[2:response_payload_len]) crc = CRC16.calculate(response_payload[2:response_payload_len])
if (response_payload[response_payload_len] == crc & 0xFF) and ( if (response_payload[response_payload_len] == crc & 0xFF) and (
response_payload[response_payload_len + 1] == (crc >> 8) & 0xFF response_payload[response_payload_len + 1] == (crc >> 8) & 0xFF
): ):

22
broadlink/helpers.py
View File

@ -1,19 +1,25 @@
"""Helper functions.""" """Helper functions and classes."""
import typing as t import typing as t
_crc16_cache = {}
class CRC16: # pylint: disable=R0903
"""Helps with CRC-16 calculation.
def crc16( CRC tables are cached for performance.
"""
_cache = {}
@classmethod
def calculate(
cls,
sequence: t.Sequence[int], sequence: t.Sequence[int],
polynomial: int = 0xA001, # Default: Modbus CRC-16. polynomial: int = 0xA001, # Modbus CRC-16.
init_value: int = 0xFFFF, init_value: int = 0xFFFF,
) -> int: ) -> int:
"""Calculate the CRC-16 of a sequence of integers.""" """Calculate the CRC-16 of a sequence of integers."""
global _crc16_cache
try: try:
crc_table = _crc16_cache[polynomial] crc_table = cls._cache[polynomial]
except KeyError: except KeyError:
crc_table = [] crc_table = []
for dividend in range(0, 256): for dividend in range(0, 256):
@ -24,7 +30,7 @@ def crc16(
else: else:
remainder = remainder >> 1 remainder = remainder >> 1
crc_table.append(remainder) crc_table.append(remainder)
_crc16_cache[polynomial] = crc_table cls._cache[polynomial] = crc_table
crc = init_value crc = init_value
for item in sequence: for item in sequence: