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