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lfsr.py
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lfsr.py
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"""
Copyright (C) 2016 Yaniv Erlich
License: GPLv3-or-later. See COPYING file for details.
"""
def lfsr(state, mask):
#Galois lfsr:
result = state
nbits = mask.bit_length()-1
while True:
result = (result << 1)
xor = result >> nbits
if xor != 0:
result ^= mask
yield result
def lfsr32p():
#this function returns a hard coded polynomial (0b100000000000000000000000011000101).
#The polynomial corresponds to 1 + x^25 + x^26 + x^30 + x^32, which is known
#to repeat only after 32^2-1 tries. Don't change unless you know what you are doing.
return 0b100000000000000000000000011000101
def lfsr32s():
#this function returns a hard coded state for the lfsr (0b001010101)
#this state is the inital position in the register. You can change it without a major implication.
return 0b001010101
def test():
#run the test to see a stream of seed by the polynomial
for pattern in lfsr(0b001, 0b100000000000000000000000011000101):
print pattern