private void ReadCompressedData(BitReader br, Stream output, TaikoLz81Tree dispIndexMapping, int index)
{
// Max displacement 0x8000; Min displacement 2
// Max length 0x102; Min length 1
var length = _counters[index];
if (_counterBitReads[index] != 0)
{
length += br.ReadBits <int>(_counterBitReads[index]);
}
var dispIndex = dispIndexMapping.ReadValue(br);
var displacement = _dispRanges[dispIndex];
if (_dispBitReads[dispIndex] != 0)
{
displacement += br.ReadBits <int>(_dispBitReads[dispIndex]);
}
if (length == 0)
{
return;
}
_circularBuffer.Copy(output, displacement, length);
}
public void Decode(Stream input, Stream output)
{
var circularBuffer = new CircularBuffer(0x8000);
using (var br = new BitReader(input, BitOrder.LeastSignificantBitFirst, 1, ByteOrder.LittleEndian))
{
var initialByte = br.ReadBits <int>(8);
// 3 value mappings
var rawValueMapping = new TaikoLz81Tree();
rawValueMapping.Build(br, 8);
var indexValueMapping = new TaikoLz81Tree();
indexValueMapping.Build(br, 6);
var dispIndexMapping = new TaikoLz81Tree();
dispIndexMapping.Build(br, 5);
while (true)
{
var index = indexValueMapping.ReadValue(br);
if (index < 0x20)
{
if (index == 0)
{
DeobfuscateData(output, initialByte);
break;
}
// Match reading
ReadCompressedData(br, output, circularBuffer, dispIndexMapping, index);
}
else
{
// Raw data reading
ReadUncompressedData(br, output, circularBuffer, rawValueMapping, index - 0x20);
}
}
}
}
private void ReadUncompressedData(BitReader br, Stream output, TaikoLz81Tree rawValueMapping, int index)
{
var counter = _counters[index];
if (_counterBitReads[index] != 0)
{
counter += br.ReadBits <int>(_counterBitReads[index]);
}
if (counter == 0)
{
return;
}
for (int i = 0; i < counter; i++)
{
var rawValue = (byte)rawValueMapping.ReadValue(br);
output.WriteByte(rawValue);
_circularBuffer.WriteByte(rawValue);
}
}
