mirror of
https://github.com/Barubary/dsdecmp.git
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261 lines
12 KiB
C#
261 lines
12 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Text;
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using System.IO;
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namespace DSDecmp.Formats.Nitro
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{
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/// <summary>
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/// Compressor and decompressor for the Huffman format used in many of the games for the
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/// newer Nintendo consoles and handhelds.
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/// </summary>
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public class Huffman : NitroCFormat
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{
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public enum BlockSize : byte { FOURBIT = 0x24, EIGHTBIT = 0x28 }
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public Huffman() : base(0) { }
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public override bool Supports(System.IO.Stream stream)
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{
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base.magicByte = (byte)BlockSize.FOURBIT;
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if (base.Supports(stream))
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return true;
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base.magicByte = (byte)BlockSize.EIGHTBIT;
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return base.Supports(stream);
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}
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public override void Decompress(Stream instream, long inLength, Stream outstream)
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{
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#region GBATEK format specification
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/*
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Data Header (32bit)
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Bit0-3 Data size in bit units (normally 4 or 8)
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Bit4-7 Compressed type (must be 2 for Huffman)
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Bit8-31 24bit size of decompressed data in bytes
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Tree Size (8bit)
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Bit0-7 Size of Tree Table/2-1 (ie. Offset to Compressed Bitstream)
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Tree Table (list of 8bit nodes, starting with the root node)
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Root Node and Non-Data-Child Nodes are:
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Bit0-5 Offset to next child node,
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Next child node0 is at (CurrentAddr AND NOT 1)+Offset*2+2
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Next child node1 is at (CurrentAddr AND NOT 1)+Offset*2+2+1
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Bit6 Node1 End Flag (1=Next child node is data)
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Bit7 Node0 End Flag (1=Next child node is data)
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Data nodes are (when End Flag was set in parent node):
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Bit0-7 Data (upper bits should be zero if Data Size is less than 8)
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Compressed Bitstream (stored in units of 32bits)
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Bit0-31 Node Bits (Bit31=First Bit) (0=Node0, 1=Node1)
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*/
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#endregion
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long readBytes = 0;
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byte type = (byte)instream.ReadByte();
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BlockSize blockSize = BlockSize.FOURBIT;
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if (type != (byte)blockSize)
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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") + "); 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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readBytes += 4;
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if (decompressedSize == 0)
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{
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sizeBytes = new byte[4];
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instream.Read(sizeBytes, 0, 4);
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decompressedSize = base.Bytes2Size(sizeBytes);
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readBytes += 4;
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}
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if (readBytes >= inLength)
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throw new NotEnoughDataException(0, decompressedSize);
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int treeSize = instream.ReadByte(); readBytes++;
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if (treeSize < 0)
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throw new InvalidDataException("The stream is too short to contain a Huffman tree.");
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treeSize = (treeSize * 2) + 1;
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if (readBytes + treeSize >= inLength)
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throw new InvalidDataException("The Huffman tree is too large for the given input stream.");
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// the relative offset may be 4 more (when the initial decompressed size is 0), but
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// since it's relative that doesn't matter, especially when it only matters if
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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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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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{
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throw new NotImplementedException();
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}
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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 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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/// <summary>
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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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/// </summary>
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/// <param name="stream">The stream to read from. It is assumed that there is (at least)
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/// one more byte available to read.</param>
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/// <param name="isData">If this node is a data-node.</param>
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/// <param name="relOffset">The offset of this node in the source data, relative to the start
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/// of the compressed file.</param>
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public HuffTreeNode(Stream stream, bool isData, long relOffset, long maxStreamPos)
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{
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/*
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Tree Table (list of 8bit nodes, starting with the root node)
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Root Node and Non-Data-Child Nodes are:
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Bit0-5 Offset to next child node,
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Next child node0 is at (CurrentAddr AND NOT 1)+Offset*2+2
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Next child node1 is at (CurrentAddr AND NOT 1)+Offset*2+2+1
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Bit6 Node1 End Flag (1=Next child node is data)
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Bit7 Node0 End Flag (1=Next child node is data)
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Data nodes are (when End Flag was set in parent node):
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Bit0-7 Data (upper bits should be zero if Data Size is less than 8)
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*/
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if (stream.Position <= maxStreamPos)
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throw new InvalidDataException("The Huffman tree does not fit in the available number of bytes.");
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int readData = stream.ReadByte();
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if (readData < 0)
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throw new StreamTooShortException();
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this.data = (byte)readData;
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this.isData = isData;
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if (!this.isData)
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{
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int offset = this.data & 0x3F;
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bool zeroIsData = (this.data & 0x40) > 0;
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bool oneIsData = (this.data & 0x80) > 0;
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// off AND NOT 1 == off XOR (off AND 1)
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long zeroRelOffset = (relOffset ^ (relOffset & 1)) + offset * 2 + 2;
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long currStreamPos = stream.Position;
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// position the stream right before the 0-node
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stream.Position += (zeroRelOffset - relOffset) - 1;
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// read the 0-node
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this.child0 = new HuffTreeNode(stream, zeroIsData, zeroRelOffset, maxStreamPos);
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// the 1-node is dircetly behind the 0-node
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this.child1 = new HuffTreeNode(stream, oneIsData, zeroRelOffset + 1, maxStreamPos);
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// reset the stream position to right behind this node's data
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stream.Position = currStreamPos;
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}
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}
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}
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}
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}
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