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# -*- coding: utf-8 -*-
#
# Linear feedback shift register
# Copyright 2012-2013 Michael Buesch <m@bues.ch>
#
# Licensed under the terms of the GNU General Public License version 2.
#
import random
class LFSR16(object):
"16-bit Galois linear feedback shift register"
DEFAULT_INIT = 0xACE1
def __init__(self, init=DEFAULT_INIT):
self.__lfsr = init & 0xFFFF
assert(self.__lfsr != 0)
def getBits(self, count):
ret, lfsr = 0, self.__lfsr
while count:
lfsr = (lfsr >> 1) ^ (-(lfsr & 1) & 0xB400)
ret, count = (ret << 1) | (lfsr & 1), count - 1
self.__lfsr = lfsr
return ret
class Simple_PRNG(LFSR16):
def __init__(self):
LFSR16.__init__(self, random.randint(1, 0xFFFF))
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