Improve crc calculation.

Use functools.reduce to facilitate checksum calculation.

pyplumio/helpers/uid.py

@@ -1,17 +1,20 @@
 """Contains an UID helpers."""
 from __future__ import annotations
 
+from functools import reduce
+from typing import Final
+
 
 def unpack_uid(message: bytearray, offset: int = 0) -> str:
     """Decode and return a complete UID string."""
     length = message[offset]
     offset += 1
     uid = message[offset : length + offset]
 
-    return _encode_base5(uid + _uid_crc(uid))
+    return _base5(uid + _crc16(uid))
 
 
-def _encode_base5(data: bytes) -> str:
+def _base5(data: bytes) -> str:
     """Encode bytes to a base5 encoded string."""
     key_string = "0123456789ABCDEFGHIJKLMNZPQRSTUV"
     number = int.from_bytes(data, "little")
@@ -23,18 +26,20 @@ def _encode_base5(data: bytes) -> str:
     return output
 
 
-def _uid_crc(message: bytes) -> bytes:
-    """Return an UID CRC."""
-    crc_value = 0xA3A3
-    for byte in message:
-        crc_value = _uid_byte(crc_value ^ byte)
+CRC: Final = 0xA3A3
+POLYNOMIAL: Final = 0xA001
 
-    return crc_value.to_bytes(byteorder="little", length=2)
+
+def _crc16(message: bytes) -> bytes:
+    """Return an UID CRC."""
+    crc16 = reduce(_crc16_byte, message, CRC)
+    return crc16.to_bytes(byteorder="little", length=2)
 
 
-def _uid_byte(byte: int) -> int:
+def _crc16_byte(crc: int, byte: int) -> int:
     """Return a byte CRC."""
+    crc ^= byte
     for _ in range(8):
-        byte = (byte >> 1) ^ 0xA001 if byte & 1 else byte >> 1
+        crc = (crc >> 1) ^ POLYNOMIAL if crc & 1 else crc >> 1
 
-    return byte
+    return crc