public uint NextSymbol()
{
if (_symbolsToNextSelector == 0)
{
_symbolsToNextSelector = 50;
_activeTree = _trees[_selectors[_nextSelector]];
_nextSelector++;
}
_symbolsToNextSelector--;
return _activeTree.NextSymbol(_bitstream);
}
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;
}
