extends Node

func ByteArray(size: int) -> PoolByteArray:
	var arr := PoolByteArray()
	arr.resize(size)
	return arr

func LZ77_decompress(rom: File, address: int) -> PoolByteArray:
	rom.seek(address)
	var header := rom.get_32()
	assert (header & 0x10 == 0x10)
	var length := header >> 8
	var output := ByteArray(length)
	var ptr := 0
	while ptr < length:
		var bitmap := rom.get_8()
		for i in range(8):
			if (bitmap >> (7-i)) & 1:
				# Buffer substitution
				var h1 := rom.get_8()
				var h2 := rom.get_8()
				var copy_len := 3 + (h1 >> 4)
				var copy_ptr := ptr - 1 - (((h1 & 0x0F)<<8) + h2)
				for j in range(copy_len):
					output[ptr] = output[copy_ptr]
					copy_ptr += 1
					ptr += 1
					if ptr >= length:
						return output
			else:
				# Literal byte
				output[ptr] = rom.get_8()
				ptr += 1
			if ptr >= length:
				return output
	return output