"""
ModbusLink CRC16校验工具模块
ModbusLink CRC16 Checksum Utils Module
"""
from typing import Union
[文档]
class CRC16Modbus:
"""
Modbus CRC16校验工具
Modbus CRC16 Check Utils Module
"""
# 预计算的CRC高位和低位表，用于快速查表计算 | Pre-computed CRC table for fast lookup
_CRC_TABLE = (0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040)
@staticmethod
def _calculate_by_table(data: Union[bytes, bytearray]) -> bytes:
"""
[内部]查表法计算
[Internal] Table lookup calculation
Args:
data: 需要计算校验码的数据帧（地址+PDU） | Data frame for checksum calculation (address+PDU)
Returns:
2字节的CRC校验码 (little-endian bytes)
2-byte CRC checksum (little-endian bytes)
"""
crc = 0xFFFF
table = CRC16Modbus._CRC_TABLE
for byte in data:
index = (crc ^ byte) & 0xFF
crc = (crc >> 8) ^ table[index]
return crc.to_bytes(2, byteorder="little")
@staticmethod
def _calculate_direct(data: Union[bytes, bytearray]) -> bytes:
"""
[内部]直接计算法
[Internal]Direct calculation
Args:
data: 需要计算校验码的数据帧（地址+PDU） | Data frame for checksum calculation (address+PDU)
Returns:
2字节的CRC校验码 (little-endian bytes)
2-byte CRC checksum (little-endian bytes)
"""
crc = 0xFFFF
for byte in data:
crc ^= byte
for _ in range(8):
if crc & 0x0001:
crc >>= 1
crc ^= 0xA001
else:
crc >>= 1
return crc.to_bytes(2, byteorder="little")
[文档]
@staticmethod
def calculate(data: Union[bytes, bytearray], use_table: bool = True) -> bytes:
"""
计算CRC16校验码
Calculate CRC16 Checksum
Args:
data: 需要计算校验码的数据帧（地址+PDU） | Data frame for checksum calculation (address+PDU)
use_table: 是否使用查表法 | Whether to use the table lookup method
Returns:
2字节的CRC校验码 (little-endian bytes)
2-byte CRC checksum (little-endian bytes)
"""
if use_table:
return CRC16Modbus._calculate_by_table(data)
else:
return CRC16Modbus._calculate_direct(data)
[文档]
@staticmethod
def validate(frame_with_crc: Union[bytes, bytearray], use_table: bool = True) -> bool:
"""
验证包含CRC的完整数据帧
Validate Complete Data Frame with CRC
Args:
frame_with_crc: 包含CRC校验码的完整数据帧 | Complete data frame containing CRC checksum
use_table: 是否使用查表法 | Whether to use the table lookup method
Returns:
如果CRC校验正确返回True，否则返回False
True if CRC verification is correct, False otherwise
"""
if len(frame_with_crc) < 3: # 至少需要1字节数据 + 2字节CRC | At least 1 byte data + 2 bytes CRC required
return False
# 分离数据和CRC | Separate data and CRC
data = frame_with_crc[:-2]
received_crc = frame_with_crc[-2:]
# 计算期望的CRC | Calculate expected CRC
expected_crc = CRC16Modbus.calculate(data, use_table)
# 比较CRC | Compare CRC
return received_crc == expected_crc