public static MemoryStream Decode(EndianBinaryReader reader)
{
if (reader.ReadUInt32() != 0x59617930) // "Yay0" Magic
{
throw new InvalidDataException("Invalid Magic, not a Yay0 File");
}
int uncompressedSize = reader.ReadInt32();
int linkTableOffset = reader.ReadInt32();
int byteChunkAndCountModifiersOffset = reader.ReadInt32();
int maskBitCounter = 0;
int currentOffsetInDestBuffer = 0;
int currentMask = 0;
byte[] uncompressedData = new byte[uncompressedSize];
do
{
// If we're out of bits, get the next mask.
if (maskBitCounter == 0)
{
currentMask = reader.ReadInt32();
maskBitCounter = 32;
}
// If the next bit is set, the chunk is non-linked and just copy it from the non-link table.
if (((uint)currentMask & (uint)0x80000000) == 0x80000000)
{
uncompressedData[currentOffsetInDestBuffer] = reader.ReadByteAt(byteChunkAndCountModifiersOffset);
currentOffsetInDestBuffer++;
byteChunkAndCountModifiersOffset++;
}
// Do a copy otherwise.
else
{
// Read 16-bit from the link table
ushort link = reader.ReadUInt16At(linkTableOffset);
linkTableOffset += 2;
// Calculate the offset
int offset = currentOffsetInDestBuffer - (link & 0xfff);
// Calculate the count
int count = link >> 12;
if (count == 0)
{
byte countModifier;
countModifier = reader.ReadByteAt(byteChunkAndCountModifiersOffset);
byteChunkAndCountModifiersOffset++;
count = countModifier + 18;
}
else
{
count += 2;
}
// Copy the block
int blockCopy = offset;
for (int i = 0; i < count; i++)
{
uncompressedData[currentOffsetInDestBuffer] = uncompressedData[blockCopy - 1];
currentOffsetInDestBuffer++;
blockCopy++;
}
}
// Get the next bit in the mask.
currentMask <<= 1;
maskBitCounter--;
} while (currentOffsetInDestBuffer < uncompressedSize);
return new MemoryStream(uncompressedData);
}
