private void Initialize(int maxSymbols)
{
int numTrees = (int)_bitstream.Read(3);
if (numTrees < 2 || numTrees > 6)
{
throw new InvalidDataException("Invalid number of tables");
}
int numSelectors = (int)_bitstream.Read(15);
if (numSelectors < 1)
{
throw new InvalidDataException("Invalid number of selectors");
}
_selectors = new byte[numSelectors];
MoveToFront mtf = new MoveToFront(numTrees, true);
for (int i = 0; i < numSelectors; ++i)
{
_selectors[i] = mtf.GetAndMove(CountSetBits(numTrees));
}
_trees = new HuffmanTree[numTrees];
for (int t = 0; t < numTrees; ++t)
{
uint[] lengths = new uint[maxSymbols];
uint len = _bitstream.Read(5);
for (int i = 0; i < maxSymbols; ++i)
{
if (len < 1 || len > 20)
{
throw new InvalidDataException("Invalid length constructing Huffman tree");
}
while (_bitstream.Read(1) != 0)
{
len = (_bitstream.Read(1) == 0) ? len + 1 : len - 1;
if (len < 1 || len > 20)
{
throw new InvalidDataException("Invalid length constructing Huffman tree");
}
}
lengths[i] = len;
}
_trees[t] = new HuffmanTree(lengths);
}
_symbolsToNextSelector = 0;
_nextSelector = 0;
}
private static int ReadBuffer(BitStream bitstream, byte[] buffer, int offset)
{
// The MTF state
int numInUse = 0;
MoveToFront moveFrontTransform = new MoveToFront();
bool[] inUseGroups = new bool[16];
for (int i = 0; i < 16; ++i)
{
inUseGroups[i] = bitstream.Read(1) != 0;
}
for (int i = 0; i < 256; ++i)
{
if (inUseGroups[i / 16])
{
if (bitstream.Read(1) != 0)
{
moveFrontTransform.Set(numInUse, (byte)i);
numInUse++;
}
}
}
// Initialize 'virtual' Huffman tree from bitstream
BZip2CombinedHuffmanTrees huffmanTree = new BZip2CombinedHuffmanTrees(bitstream, numInUse + 2);
// Main loop reading data
int readBytes = 0;
while (true)
{
uint symbol = huffmanTree.NextSymbol();
if (symbol < 2)
{
// RLE, with length stored in a binary-style format
uint runLength = 0;
int bitShift = 0;
while (symbol < 2)
{
runLength += (symbol + 1) << bitShift;
bitShift++;
symbol = huffmanTree.NextSymbol();
}
byte b = moveFrontTransform.Head;
while (runLength > 0)
{
buffer[offset + readBytes] = b;
++readBytes;
--runLength;
}
}
if (symbol <= numInUse)
{
// Single byte
byte b = moveFrontTransform.GetAndMove((int)symbol - 1);
buffer[offset + readBytes] = b;
++readBytes;
}
else if (symbol == numInUse + 1)
{
// End of block marker
return readBytes;
}
else
{
throw new InvalidDataException("Invalid symbol from Huffman table");
}
}
}