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#!/usr/bin/python
import sys
_hammingCalculateParityLowNibble = [0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7]
_hammingCalculateParityHighNibble = [0, 9, 10, 3, 11, 2, 1, 8, 12, 5, 6, 15, 7, 14, 13, 4]
def HammingCalculateParity128(byte):
return _hammingCalculateParityLowNibble[byte&0x0F] ^ _hammingCalculateParityHighNibble[byte >> 4]
def HammingCalculateParity2416(first, second):
return HammingCalculateParity128(second) << 4 | HammingCalculateParity128(first)
output = ""
bytepos = 0
oldbyte = None
# Read bytewise
f = open(sys.argv[1])
for byte in f.read():
output += byte
oldbyte = byte
bytepos += 1
if bytepos == 2:
bytepos = 0
output += str(HammingCalculateParity2416(ord(oldbyte), ord(byte)))
if bytepos == 1:
output += "\x00"
output += str(HammingCalculateParity2416(ord(oldbyte), ord("\x00")))
print output
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