Hamming ([24,48] so far)

hamming.py

#!/usr/bin/env python
# Copyright 2018 James Edington
# Permission is given to use, modify,
# and redistribute (including modifications)
# in accordance with the MIT license available at
#   https://opensource.org/licenses/MIT

# Version 0.0.3, May 22 2018

def __main__():
	from sys import argv,getfilesystemencoding
	from codecs import register_error
	if len(argv) == 1:
		# Being run with no arguments
		__demo__()
	elif len(argv) == 3:
		raise NotImplementedError("STDIO/CMD interface TODO!\nFor now, just use the API.")
		# Three arguments, assuming first is message
		code=(int([2]),int(argv[3]))
		#enc=getfilesystemencoding()
		enc='utf-8'
		register_error(enc, lambda e:(e.object[e.start:e.end].encode(enc),e.end))
		# https://stackoverflow.com/q/50475239/1874170#comment87965447_50475239
		data=argv[1].encode('iso-8859-1', errors=enc)

def __demo__():
		code=(24,18)
		# 0/4  |  192/255  |  168/255
		data = 0b001100000010101000.to_bytes(3, byteorder='big')
		print('Data in:\t{}'.format(' ' * (code[1]%8) + ' '.join([format(i, "08b") for i in data])[code[1]%8:]))
		encoded = hamming(data, code)
		print('Encoded:\t{}'.format(' ' * (code[0]%8) + ' '.join([format(i, "08b") for i in encoded])[code[0]%8:]))

def _xor(items):
	i=0x00
	for item in items:
	 i ^= item
	return i

_mask_le = lambda B, i: B & 0b0000001 << i
# _index_le(0b0001, 0) == 1 and _index_le(0b1011, 2) == 0
# Negative indices TODO, perhaps infeasible due to non-existant "left" boundary
_index_le = lambda B, i: _mask_le(B,i) >> i

def hamming(data, code):
	assert code in check_mask and code in encode_table
	# Ensure the data is of appropriate length
	assert -(-code[1] // 8) == len(data) # https://stackoverflow.com/a/33300093/1874170
	
	# https://pdc.ro.nu/hamming.html
	check_mask={
	 (24,18):[
	  (1,[17,15,13,11,10, 8, 6, 4, 3, 1, 0]),
	  (1,[17,16,13,12,10, 9, 6, 5, 3, 2, 0]),
	  (1,[17,16,15,14,10, 9, 8, 7, 3, 2, 1]),
	  (1,[10, 9, 8, 7, 6, 5, 4]),
	  (1,[17,16,15,14,13,12,11]),
	  (0,[17,14,12,11,10, 7, 5, 4, 2, 1, 0])
	 ]
	}
	
	encode_table={
	 (24,18):[
	  [( 1, 3),( 0, 3),( 0, 2),( 0, 1),( 1, 2),( 0, 0),( 1, 1),( 1, 0)],
	  [( 1, 4),( 0,10),( 0, 9),( 0, 8),( 0, 7),( 0, 6),( 0, 5),( 0, 4)],
	  [( 1, 5),( 0,17),( 0,16),( 0,15),( 0,14),( 0,13),( 0,12),( 0,11)]
	 ]
	}
	
	chex_int=0x00
	data_int=int.from_bytes(data, byteorder='big')
	I=0
	for B in check_mask[code]:
		chex_int ^= (
		 _xor(
		  [B[0]] +
			[_index_le(data_int, i) for i in B[1]]
		 ) << I
		)
		I += 1
	
	encoded=bytearray()
	bc_int=(data_int,chex_int)
	I=0
	for B in encode_table[code]:
		x=0x00
		i=0
		for b in B:
			x ^= _index_le(bc_int[b[0]], b[1]) << i
			i += 1
		encoded.append(x)
		I += 1
	return bytes(encoded)

__name__ == "__main__" and __main__()