Naive implementation of a pseudo random binary sequence generator.

prbs.py

import collections
from operator import xor


class PRBS(object):
    """Generates PRBS sequences.
    
    E.g.::
    
        # Generate a single period of a prbs7 sequence with
        # polynom x**7 + x**6 + 1
        prbs7_gen = PRBS([7, 6], [0,0,0,0,0,0,1])
        prbs7_seq = [i for i in it.islice(prbs7_gen, len(prbs7_gen))]
        
        # Generate two periods of a prbs9 sequence with
        # polynom x**9 + x**5 + 1
        prbs9_gen = PRBS([9, 5], [0,0,0,0,0,0,0,0,1])
        prbs9_seq = [i for i in it.islice(prbs9_gen, len(prbs9_gen))]
    
    """
    def __init__(self, taps, sequence):
        self.taps = taps
        self._buffer = collections.deque(sequence, maxlen=len(sequence))
        
    def __len__(self):
        return 2**len(self._buffer) - 1
    
    def __iter__(self):
        return self
    
    def next(self):
        out = self._buffer[-1]
        
        i, j = self.taps
        a0, a1 = self._buffer[i - 1], self._buffer[j - 1]
        self._buffer.appendleft(xor(a0, a1))
        return a0