# -*- coding: utf-8 -*-
#! /usr/bin/env python3
import crcmod.predefined
class crc16:
def __init__(self):
pass
def crc16Modbus(self, bytes_data, start_pos, stop_pos, invert=False):
a = 0xFFFF
b = 0xA001
for i in range(start_pos, stop_pos):
a ^= bytes_data[i]
for j in range(8):
last = a % 2
a >>= 1
if last == 1:
a ^= b
return (a << 8 & 0xff00) | a >> 8 if invert == False else a
def crc16Modbus2(self, bytes_data, start_pos, stop_pos, invert=False):
data = bytes_data[start_pos:stop_pos]
modus_crc_func = crcmod.predefined.mkCrcFun('modbus')
res = modus_crc_func(data)
return (res << 8 & 0xff00) | res >> 8 if invert == False else res
def crc16Xmodem(self, bytes_data, start_pos, stop_pos, invert=False):
wcrc = 0
for i in range(start_pos, stop_pos):
data = bytes_data[i]
for j in range(8):
treat = data & 0x80
data <<= 1
bcrc = (wcrc >> 8) & 0x80
wcrc <<= 1
wcrc = wcrc & 0xffff
if (treat != bcrc):
wcrc ^= 0x1021
return wcrc if invert == False else (wcrc << 8 & 0xff00) | wcrc >> 8
def crc16Xmodem2(self, bytes_data, start_pos, stop_pos, invert=False):
data = bytes_data[start_pos:stop_pos]
xmodem_crc_func = crcmod.predefined.mkCrcFun('xmodem')
res = xmodem_crc_func(data)
return res if invert == False else (res << 8 & 0xff00) | res >> 8
# debug type: singel file
# file name: mycrc16.py
# file version: v0.0
# debug time: 2020.8.26
if __name__ == '__main__':
crc16_test = crc16()
print(hex(crc16_test.crc16Modbus(bytes('123456789', encoding='utf8'), 0, 9)))
print(hex(crc16_test.crc16Modbus2(bytes('123456789', encoding='utf8'), 0, 9)))
print(hex(crc16_test.crc16Xmodem(bytes('123456789', encoding='utf8'), 0, 9)))
print(hex(crc16_test.crc16Xmodem2(bytes('123456789', encoding='utf8'), 0, 9)))
'''
注意：
参数说明
入参：bytes_data 待校验字节串数据,
start_pos 校验数据起始位置
stop_pos 校验数据结束位置
invert=False 校验结果默认低字节在前，如果invert=True则高字节在前
出参：
输出2个字节的校验结果
crc16Modbus是自己实现， crc16Modbus2是调用库实现；
crc16Xmodem2是自己实现， crc16Xmodem2是调用库实现；
'''