decompress.py

import os
import sys

def decompress(f, offset, table_length):
    decompressed = []
    f.seek(offset, os.SEEK_SET)
    while True:
        if f.tell() == offset + table_length:
            return bytes(decompressed)

        tag = f.read(1)[0]

        tag_clen, tag_coffset, tag_len = tag >> 4, (tag >> 2) & 3, tag & 3
        print(f'{tag=:#04x}, {tag_clen=:#04x}, {tag_coffset=:#04x}, {tag_len=:#04x}')
        
        length = tag_len
        if tag_len == 0:
            length = f.read(1)[0] + 3

        clen = tag_clen
        if tag_clen == 0xf:
            clen = f.read(1)[0] + 0xf

        print(f'  -> data {length=:#04x}')
        data = f.read(length - 1)
        decompressed += data

        if clen != 0:
            coffset_low = f.read(1)[0]

            coffset_high = tag_coffset
            if tag_coffset == 3:
                coffset_high = f.read(1)[0]

            coffset = (coffset_high << 8) | coffset_low
            print(f'  -> compressed {clen=:#04x} {coffset=:#06x}')

            idx = len(decompressed) - coffset
            for _ in range(clen + 2):
                decompressed.append(decompressed[idx])
                idx += 1

with open(sys.argv[1], 'rb') as f:
    # offset into the file of the compressed data
    TABLE = 0x14058b
    # the length * 2 that comes from the first init table that told you where
    # the compressed data was
    LENGTH = 0x1cce >> 1

    data = decompress(f, TABLE, LENGTH)
with open(sys.argv[2], 'wb') as f:
    f.write(data)