34 lines
1.3 KiB
GDScript3
34 lines
1.3 KiB
GDScript3
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static func decompress_lzss(rom: StreamPeer, uncompressed_length:=0) -> PoolByteArray:
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# Algorithm from http://slickproductions.org/slickwiki/index.php/Noisecross:Final_Fantasy_V_Compression
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# Reuploaded at https://www.ff6hacking.com/ff5wiki/index.php/Compression#Decompression_Type_02_.28LZSS.29
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if not uncompressed_length:
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uncompressed_length = rom.get_u16()
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var output := PoolByteArray()
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var buffer := PoolByteArray()
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buffer.resize(0x800)
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buffer.fill(0)
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var buffer_p := 0x07DE
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while len(output) < uncompressed_length:
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var bitmap_byte := rom.get_u8()
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for i in range(8):
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var bit := (bitmap_byte >> i) & 1
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if bit:
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var b := rom.get_u8()
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output.append(b)
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buffer[buffer_p] = b
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buffer_p = (buffer_p+1) % 0x800
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else:
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# Reuse bytes from previously decompressed buffer
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var b1 := rom.get_u8() # lower 8 bits of offset
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var b2 := rom.get_u8() # upper 3 bits of offset, 5bit length-3
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var offset := b1 | ((b2 & 0xE0) << 3) # 11bit is [0, 0x7FF]
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var length := (b2 & 0x1F) + 3 # The +3 is likely because the compression overhead makes this a sensible minimum
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for j in range(length):
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var b := buffer[offset]
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output.append(b)
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buffer[buffer_p] = b
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buffer_p = (buffer_p+1) % 0x800
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offset = (offset+1) % 0x800
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output.resize(uncompressed_length)
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return output
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