Implement Zebra CRC16

tests/test_zebrafy_crc.py

@@ -39,21 +39,15 @@ def setUp(self):
         super().setUp()
         self.crc = CRC(b"Python is fun")
 
-    def test_crc_data_bytes(self):
+    def test_crc_data_bytes(self) -> None:
         """Test CRC data bytes input."""
         with self.assertRaises(ValueError):
             CRC(None)
         with self.assertRaises(TypeError):
             CRC(123)
 
-    def test_crc_poly(self):
-        """Test CRC polynomial input."""
-        self.assertEqual(self.crc.poly, 0x8408)
-        with self.assertRaises(ValueError):
-            self.crc.poly = None
-        with self.assertRaises(TypeError):
-            self.crc.poly = "Test"
-
+    def test_crc_hex(self) -> None:
+        self.assertEqual(self.crc.get_crc_hex_string(), "A641")
 
 if __name__ == "__main__":
     unittest.main()

zebrafy/crc.py

@@ -29,22 +29,54 @@
 # 3. Local imports in the relative form:
 
 
+CRC_TABLE = [
+    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
+    0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
+    0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
+    0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
+    0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
+    0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
+    0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
+    0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
+    0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
+    0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
+    0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
+    0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
+    0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
+    0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
+    0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
+    0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
+    0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
+    0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
+    0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
+    0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
+    0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
+    0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
+    0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
+    0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
+    0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
+    0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
+    0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
+    0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
+    0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
+    0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
+    0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
+    0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0
+]
+
+
 class CRC:
     """
-    Utility class to calculate CRC-16-CCITT algorithm across the received data bytes.
+    Utility class to calculate Zebra CRC-16 algorithm across the received data bytes.
 
-    CRC-16-CCITT polynomial representation: x^{16} + x^{12} + x^5 + 1
+    It is very similar to XMODEM CRC16, but it does not augment, and this has different results.
+    https://www.zebra.com/content/dam/support-dam/en/documentation/unrestricted/guide/software/cpcl-link-os-pg-en.pdf
 
     :param data_bytes: Bytes object for which to calculate CRC
-    :param poly: Reversed polynomial representation for CRC-16-CCITT calculation, \
-    defaults to ``0x8408``
     """
 
-    def __init__(self, data_bytes: bytes, poly: int = None):
+    def __init__(self, data_bytes: bytes):
         self.data_bytes = data_bytes
-        if poly is None:
-            poly = 0x8408
-        self.poly = poly
 
     data_bytes = property(operator.attrgetter("_data_bytes"))
 
@@ -58,41 +90,24 @@ def data_bytes(self, d):
             )
         self._data_bytes = d
 
-    poly = property(operator.attrgetter("_poly"))
-
-    @poly.setter
-    def poly(self, p):
-        if p is None:
-            raise ValueError("Polynomial cannot be empty.")
-        if not isinstance(p, int):
-            raise TypeError(f"Polynomial must be a valid integer. {type(p)} was given.")
-        self._poly = p
-
-    def _get_crc16_ccitt(self) -> int:
+    def _get_zebra_crc16(self) -> int:
         """
-        Calculate CRC-16-CCITT Algorithm.
+        Calculate Zebra CRC-16 Algorithm.
 
-        :returns: CRC-16-CCITT
+        :returns: Zebra CRC-16
         """
         data = bytearray(self._data_bytes)
-        crc = 0xFFFF
-        for b in data:
-            cur_byte = 0xFF & b
-            for _ in range(0, 8):
-                if (crc & 0x0001) ^ (cur_byte & 0x0001):
-                    crc = (crc >> 1) ^ self._poly
-                else:
-                    crc >>= 1
-                cur_byte >>= 1
-        crc = ~crc & 0xFFFF
-        crc = (crc << 8) | ((crc >> 8) & 0xFF)
+        crc = 0x0000
+        for cur_byte in data:
+            index = (cur_byte ^ (crc >> 8)) & 0xFF
+            crc = CRC_TABLE[index] ^ (crc << 8)
 
         return crc & 0xFFFF
 
     def get_crc_hex_string(self) -> str:
         """
-        Get CRC-16-CCITT as four digit zero padding hexadecimal string.
+        Get Zebra CRC-16 as four digit zero padding hexadecimal string.
 
-        :returns: CRC-16-CCITT as four digit zero padding hexadecimal string
+        :returns: Zebra CRC-16 as four digit zero padding hexadecimal string
         """
-        return f"{self._get_crc16_ccitt():04X}"
+        return f"{self._get_zebra_crc16():04X}"