const int ChunkSize = 128 * 1024; // 128Kb throttling
public EncodingToken CreateEncodingToken(IEncodingInputStream inputStream, CancellationToken cancellationToken)
{
Guard.IsNotNull(inputStream, nameof(inputStream));
WeightsTable weightsTable = BuildWeightsTable(inputStream, cancellationToken);
HuffmanTreeBase huffmanTree = BuildHuffmanTree(weightsTable);
CodingTable codingTable = BuildCodingTable(huffmanTree);
return(new EncodingToken(weightsTable, huffmanTree, codingTable));
}
public void Decode(IDecodingInputStream inputStream, WeightsTable weightsTable, IDecodingOutputStream outputStream, long sequenceLength, CancellationToken cancellationToken, IProgressHandler progress)
{
Guard.IsNotNull(inputStream, nameof(inputStream));
Guard.IsNotNull(weightsTable, nameof(weightsTable));
Guard.IsNotNull(outputStream, nameof(outputStream));
Guard.IsNotNegative(sequenceLength, nameof(sequenceLength));
HuffmanTreeBase tree = new HuffmanEncoder().BuildHuffmanTree(weightsTable);
Decode(inputStream, tree, outputStream, sequenceLength, cancellationToken, progress);
}
public WeightsTable BuildWeightsTable(IEncodingInputStream inputStream, CancellationToken cancellationToken)
{
Guard.IsNotNull(inputStream, nameof(inputStream));
WeightsTable weightsTable = new WeightsTable();
int currentChunkSz = 0;
while (inputStream.ReadSymbol(out byte symbol))
{
weightsTable.TrackSymbol(symbol);
if (++currentChunkSz == ChunkSize)
{
cancellationToken.ThrowIfCancellationRequested();
currentChunkSz = 0;
}
}
return(weightsTable);
}
public HuffmanTreeBase BuildHuffmanTree(WeightsTable weightsTable)
{
Guard.IsNotNull(weightsTable, nameof(weightsTable));
HuffmanTreeNodePriorityQueue priorityQueue = new HuffmanTreeNodePriorityQueue();
foreach (WeightedSymbol weightedSymbol in weightsTable)
{
priorityQueue.Insert(weightedSymbol.Weight, new HuffmanTreeNode(weightedSymbol));
}
if (priorityQueue.Size == 0)
{
return(EmptyHuffmanTree.Instance);
}
while (priorityQueue.Size > 1)
{
var lNode = priorityQueue.DeleteMinimumValue();
var rNode = priorityQueue.DeleteMinimumValue();
long weight = lNode.Value.Weight + rNode.Value.Weight;
var internalNode = new HuffmanTreeNode(new WeightedSymbol(0, weight), lNode, rNode);
priorityQueue.Insert(weight, internalNode);
}
return(new HuffmanTree(priorityQueue.GetMinimumValue()));
}
public EncodingToken(WeightsTable weightsTable, HuffmanTreeBase huffmanTree, CodingTable codingTable)
{
CodingTable = codingTable;
WeightsTable = weightsTable;
HuffmanTree = huffmanTree;
}
