a redundant bits encoder

redundant_enc.py

"""
    a basic redundant bits encoder-decoder
"""

import json
import random
import sys

SAMPLE_PAYLOAD = {"foo": 1, "bar": 2}
FLIP_PROB = 0.05

def dict_to_bytes(d):
    """ dict to bytes """
    return json.dumps(d).encode()

def bytes_to_bits(bytes_obj):
    """ bytes to a binary string """
    return bin(int.from_bytes(bytes_obj, byteorder=sys.byteorder))[2:]

def bits_to_bytes(bits):
    """ a binary string to bytes """
    return int(bits, 2).to_bytes((len(bits) + 7) // 8, byteorder=sys.byteorder)

def redundant_enc(bits):
    """ encode a binary string by repeating each bit 3 times """
    enc_bits = ''
    for b in bits:
        enc_bits += b * 3
    return enc_bits

def random_noise(bits, p):
    """ flip each bit with probability p"""
    modified_bits = ''
    for b in bits:
        if random.uniform(0, 1) <= p:
            modified_bits += str((int(b) + 1) % 2)
        else:
            modified_bits += b
    return modified_bits

def redundant_decode(enc_bits):
    """ decode a binary string by taking the majority vote of each consecutive set of 3 bits"""
    dec_bits = ''
    n = len(enc_bits)
    i = 0
    while i < n:
        enc_part = enc_bits[i:i+3]
        k = sum([int(b) for b in enc_part])
        if k > 1:
            dec_bits += '1'
        else:
            dec_bits += '0'
        i += 3
    return dec_bits


bytes_payload = dict_to_bytes(SAMPLE_PAYLOAD)
bits_payload = bytes_to_bits(bytes_payload)
print(f"bits payload: {bits_payload}")
enc_bits = redundant_enc(bits_payload)
print(f"encoded bits: {enc_bits}")
modified_bits = random_noise(enc_bits, FLIP_PROB)
print(f"modified bits: {modified_bits}")
dec_bits = redundant_decode(modified_bits)
print(f"decoded bits: {dec_bits}")
dec_bytes = bits_to_bytes(dec_bits)
print(f"decoded bytes: {dec_bytes}")