Mercurial > touhou
view pytouhou/utils/lzss.py @ 0:6b2c7af2384c
Hello Gensokyo _o/
author | Thibaut Girka <thib@sitedethib.com> |
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date | Sun, 31 Jul 2011 21:32:12 +0200 |
parents | |
children | ab826bc29aa2 |
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def decompress(bitstream, size, dictionary_size=0x2000, offset_size=13, length_size=4, minimum_match_length=3): out_data = [] dictionary = [0] * dictionary_size dictionary_head = 1 while len(out_data) < size: flag = bitstream.read_bit() if flag: # The `flag` bit is set, indicating the upcoming chunk of data is a literal # Add it to the uncompressed file, and store it in the dictionary byte = bitstream.read(8) dictionary[dictionary_head] = byte dictionary_head = (dictionary_head + 1) % dictionary_size out_data.append(byte) else: # The `flag` bit is not set, the upcoming chunk is a (offset, length) tuple offset = bitstream.read(offset_size) length = bitstream.read(length_size) + minimum_match_length if (offset, length) == (0, 0): break for i in range(offset, offset + length): out_data.append(dictionary[i % dictionary_size]) dictionary[dictionary_head] = dictionary[i % dictionary_size] dictionary_head = (dictionary_head + 1) % dictionary_size return b''.join(chr(byte) for byte in out_data)