Python-检查帧的CRC-16-CCITT
下面是一些检查给定消息的CRC的代码。结果为0表示未发现故障。参考:http://www.ross.net/crc/download/crc_v3.txt
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- def checkCRC(message):
- #CRC-16-CITT poly, the CRC sheme used by ymodem protocol
- poly = 0x1021
- #16bit operation register, initialized to zeros
- reg = 0x0000
- #pad the end of the message with the size of the poly
- message += '\x00\x00'
- #for each bit in the message
- for byte in message:
- mask = 0x80
- while(mask > 0):
- #left shift by one
- reg<<=1
- #input the next bit from the message into the right hand side of the op reg
- if ord(byte) & mask:
- reg += 1
- mask>>=1
- #if a one popped out the left of the reg, xor reg w/poly
- if reg > 0xffff:
- #eliminate any one that popped out the left
- reg &= 0xffff
- #xor with the poly, this is the remainder
- reg ^= poly
- return reg
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