mirror of https://github.com/notwa/mm
52 lines
1.2 KiB
Python
52 lines
1.2 KiB
Python
# decoder ripped from: http://www.amnoid.de/gc/yaz0.txt
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def decode(comp):
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src = 16 # skip header
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dst = 0
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valid = 0 # bit count
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curr = 0 # code byte
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assert(comp[:4] == b'Yaz0')
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assert(comp[8:12] == b'\x00\x00\x00\x00')
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assert(comp[12:16] == b'\x00\x00\x00\x00')
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# we could use struct but eh we only need it once
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size = comp[4]*0x1000000 + comp[5]*0x10000 + comp[6]*0x100 + comp[7]
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uncomp = bytearray(size)
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while dst < size:
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if not valid:
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curr = comp[src]
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src += 1
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valid = 8
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if curr & 0x80:
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uncomp[dst] = comp[src]
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dst += 1
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src += 1
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else:
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byte1 = comp[src]
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byte2 = comp[src + 1]
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src += 2
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dist = ((byte1 & 0xF) << 8) | byte2
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copy = dst - (dist + 1)
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assert(copy >= 0)
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n = byte1 >> 4
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if n:
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n += 2
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else:
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n = comp[src] + 0x12
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src += 1
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for i in range(n):
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uncomp[dst] = uncomp[copy]
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copy += 1
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dst += 1
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curr <<= 1
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valid -= 1
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return uncomp
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