lfsr.py

#!/usr/bin/env python3
#-*- coding: utf-8 -*-

# Computes bit parity. When x represented as binary number
# has odd number of ones, 1 is returned. Otherwise 0 is returned.
def parity(x):
	i = 1
	y = x
	while x:
		x >>= i
		y ^= y >> i
		i <<= 1
	return y & 1

# bits - number of bits in register, used to know where to put incoming bit.
def next_word(previous_word, polynomial, bits):
	return (previous_word >> 1) | (parity(previous_word & polynomial) << (bits-1))