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C#: completed the implementation for the decompression of the Huffman format.
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@ -56,7 +56,7 @@ namespace DSDecmp.Formats.Nitro
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blockSize = BlockSize.EIGHTBIT;
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if (type != (byte)blockSize)
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throw new InvalidDataException("The provided stream is not a valid Huffman "
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+ "compressed stream (invalid type 0x" + type.ToString("X") + ")");
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+ "compressed stream (invalid type 0x" + type.ToString("X") + "); unknown block size.");
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byte[] sizeBytes = new byte[3];
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instream.Read(sizeBytes, 0, 3);
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int decompressedSize = base.Bytes2Size(sizeBytes);
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@ -84,7 +84,76 @@ namespace DSDecmp.Formats.Nitro
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// the given value is odd or even.
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HuffTreeNode rootNode = new HuffTreeNode(instream, false, 5, instream.Position + treeSize);
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throw new NotImplementedException();
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int data = 0;
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byte bitsLeft = 0;
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// a cache used for writing when the block size is four bits
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int cachedByte = -1;
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int currentSize = 0;
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HuffTreeNode currentNode = rootNode;
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while (currentSize < decompressedSize)
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{
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#region find the next reference to a data node
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while (!currentNode.IsData)
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{
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// if there are no bits left to read in the data, get a new byte from the input
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if (bitsLeft == 0)
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{
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if (readBytes >= inLength)
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throw new NotEnoughDataException(currentSize, decompressedSize);
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// the spec indicates the data is read in groups of four bytes, but because of
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// the order the bits are read in, we might as well read one byte at a time.
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data = instream.ReadByte();
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if (data < 0)
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throw new StreamTooShortException();
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bitsLeft = 8;
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}
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// get the next bit
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bitsLeft--;
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bool nextIsOne = (data & (1 << bitsLeft)) > 0;
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// go to the next node, the direction of the child depending on the value of the current/next bit
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currentNode = nextIsOne ? currentNode.Child1 : currentNode.Child0;
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}
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#endregion
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#region write the data in the current node (when possible)
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switch (blockSize)
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{
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case BlockSize.EIGHTBIT:
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{
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// just copy the data if the block size is a full byte
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outstream.WriteByte(currentNode.Data);
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currentSize++;
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break;
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}
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case BlockSize.FOURBIT:
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{
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// cache the first half of the data if the block size is a half byte
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if (cachedByte < 0)
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{
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cachedByte = currentNode.Data << 4;
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}
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else
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{
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// if we already cached a half-byte, combine the two halves and write the full byte.
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cachedByte |= currentNode.Data;
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outstream.WriteByte((byte)cachedByte);
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currentSize++;
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// be sure to forget the two written half-bytes
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cachedByte = -1;
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}
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break;
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}
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default:
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throw new Exception("Unknown block size " + blockSize.ToString());
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}
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#endregion
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// make sure to start over next round
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currentNode = rootNode;
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}
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}
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public override void Compress(Stream instream, long inLength, Stream outstream)
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@ -97,10 +166,14 @@ namespace DSDecmp.Formats.Nitro
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public class HuffTreeNode
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{
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/// <summary>
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/// The data contained in this node. May not mena anything when <code>isData == false</code>
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/// The data contained in this node. May not mean anything when <code>isData == false</code>
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/// </summary>
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private byte data;
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/// <summary>
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/// The data contained in this node. May not mean anything when <code>isData == false</code>
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/// </summary>
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public byte Data { get { return this.data; } }
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/// <summary>
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/// A flag indicating if this ia a 'child1' of another node.
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/// </summary>
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private bool isOne;
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@ -108,15 +181,27 @@ namespace DSDecmp.Formats.Nitro
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/// A flag indicating if this node contains data. If not, this is not a leaf node.
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/// </summary>
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private bool isData;
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/// <summary>
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/// Returns true if this node represents data.
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/// </summary>
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public bool IsData { get { return this.isData; } }
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/// <summary>
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/// The child of this node at side 0
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/// </summary>
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private HuffTreeNode child0;
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/// <summary>
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/// The child of this node at side 0
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/// </summary>
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public HuffTreeNode Child0 { get { return this.child0; } }
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/// <summary>
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/// The child of this node at side 1
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/// </summary>
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private HuffTreeNode child1;
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/// <summary>
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/// The child of this node at side 1
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/// </summary>
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public HuffTreeNode Child1 { get { return this.child1; } }
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/// <summary>
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/// Creates a new node in the Huffman tree.
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