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; }