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CRC8.py

02.18.2007
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#!/usr/bin/env python

__author__="Andrew Pennebaker (andrew.pennebaker@gmail.com)"
__date__="23 Dec 2005 - 17 Jul 2006"
__copyright__="Copyright 2006 Andrew Pennebaker"
__version__="0.3"
__credits__="From the PyPy project"
__URL__="http://snippets.dzone.com/posts/show/3543"

import HashFunction

class CRC8(HashFunction.HashFunction):
	BLOCK_SIZE=1
	DIGEST_SIZE=1

	INIT=0x00
	SUM_REQ="Sum >= 0"

	TEST_DATA="abc"
	TEST_HASH=0x8b

	TABLE=[
		0x00, 0x07, 0x0e, 0x09, 0x1c, 0x1b, 0x12, 0x15,
		0x38, 0x3f, 0x36, 0x31, 0x24, 0x23, 0x2a, 0x2d,
		0x70, 0x77, 0x7e, 0x79, 0x6c, 0x6b, 0x62, 0x65,
		0x48, 0x4f, 0x46, 0x41, 0x54, 0x53, 0x5a, 0x5d,
		0xe0, 0xe7, 0xee, 0xe9, 0xfc, 0xfb, 0xf2, 0xf5,
		0xd8, 0xdf, 0xd6, 0xd1, 0xc4, 0xc3, 0xca, 0xcd,
		0x90, 0x97, 0x9e, 0x99, 0x8c, 0x8b, 0x82, 0x85,
		0xa8, 0xaf, 0xa6, 0xa1, 0xb4, 0xb3, 0xba, 0xbd,
		0xc7, 0xc0, 0xc9, 0xce, 0xdb, 0xdc, 0xd5, 0xd2,
		0xff, 0xf8, 0xf1, 0xf6, 0xe3, 0xe4, 0xed, 0xea,
		0xb7, 0xb0, 0xb9, 0xbe, 0xab, 0xac, 0xa5, 0xa2,
		0x8f, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9d, 0x9a,
		0x27, 0x20, 0x29, 0x2e, 0x3b, 0x3c, 0x35, 0x32,
		0x1f, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0d, 0x0a,
		0x57, 0x50, 0x59, 0x5e, 0x4b, 0x4c, 0x45, 0x42,
		0x6f, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7d, 0x7a,
		0x89, 0x8e, 0x87, 0x80, 0x95, 0x92, 0x9b, 0x9c,
		0xb1, 0xb6, 0xbf, 0xb8, 0xad, 0xaa, 0xa3, 0xa4,
		0xf9, 0xfe, 0xf7, 0xf0, 0xe5, 0xe2, 0xeb, 0xec,
		0xc1, 0xc6, 0xcf, 0xc8, 0xdd, 0xda, 0xd3, 0xd4,
		0x69, 0x6e, 0x67, 0x60, 0x75, 0x72, 0x7b, 0x7c,
		0x51, 0x56, 0x5f, 0x58, 0x4d, 0x4a, 0x43, 0x44,
		0x19, 0x1e, 0x17, 0x10, 0x05, 0x02, 0x0b, 0x0c,
		0x21, 0x26, 0x2f, 0x28, 0x3d, 0x3a, 0x33, 0x34,
		0x4e, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5c, 0x5b,
		0x76, 0x71, 0x78, 0x7f, 0x6a, 0x6d, 0x64, 0x63,
		0x3e, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2c, 0x2b,
		0x06, 0x01, 0x08, 0x0f, 0x1a, 0x1d, 0x14, 0x13,
		0xae, 0xa9, 0xa0, 0xa7, 0xb2, 0xb5, 0xbc, 0xbb,
		0x96, 0x91, 0x98, 0x9f, 0x8a, 0x8d, 0x84, 0x83,
		0xde, 0xd9, 0xd0, 0xd7, 0xc2, 0xc5, 0xcc, 0xcb,
		0xe6, 0xe1, 0xe8, 0xef, 0xfa, 0xfd, 0xf4, 0xf3
	]

	def __init__(self, sum=0x00):
		self.sum=sum^0xff

	def sumValid(self, sum):
		return sum>=0

	def _update(self, b):
		self.sum=self.TABLE[self.sum^b]

	def digest(self):
		return self.sum^0xff

	def format(self, data):
		return "%02x" % (data)

	def unformat(self, hash):
		return int(hash, 16)

if __name__=="__main__":
	HashFunction.main(CRC8)