# # Sam Hadow - Huffman-py # Copyright (C) 2023 # # This program is free software: you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program. If not, see . # import re def huffman_decode(encodedData, current_node): root = current_node decodedOutput = [] # if single node in source tree (unique char in the text) if (not root.left and not root.right): string = ''.join([root.char for _ in encodedData]) return string # else for x in encodedData: if x == '1': current_node = current_node.right elif x == '0': current_node = current_node.left # If internal node we keep going down, else (a leaf) we can decode a part of the binary. try: # internal node if current_node.left.char == None and current_node.right.char == None: pass except AttributeError: # leaf decodedOutput.append(current_node.char) current_node = root if current_node != root and (current_node.right !=None or current_node.left != None): # If we end on an internal node then source tree wasn't the correct tree. raise ValueError ("Tree and binary don't correspond.") string = ''.join([str(item) for item in decodedOutput]) return string def decode_from_dict(encodedData, dict_): # we have a Dict like this: {char:code} # we convert it to a Dict like that: {code:char} (both codes and chars are unique) dict_ = {value:key for key,value in dict_.items()} text = str(encodedData) # we check if we have a binary invalid_char = re.compile('[^01]') if invalid_char.search(text): raise TypeError ('Input text must be a binary.') decoded = '' sorted_dict = dict(sorted(dict_.items(), key=lambda x: len(x[0]), reverse=False)) while len(text) > 0: for i,binary in enumerate(sorted_dict.keys()): if binary == text[0:len(binary)]: # If we have this binary part in our Dict we can decode a char decoded += sorted_dict[binary] # delete decoded part text = text[len(binary):] # next while iteration break # if nothing corresponds then it's not the correct Dict elif i == len(sorted_dict.keys())-1: raise ValueError ("Can't convert text with current Dict.") return decoded