dsdecmp/CSharp/DSDecmp/Formats/Nitro/Huffman.cs

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C#
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using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
namespace DSDecmp.Formats.Nitro
{
/// <summary>
/// Compressor and decompressor for the Huffman format used in many of the games for the
/// newer Nintendo consoles and handhelds.
/// </summary>
public class Huffman : NitroCFormat
{
public enum BlockSize : byte { FOURBIT = 0x24, EIGHTBIT = 0x28 }
public Huffman() : base(0) { }
public override bool Supports(System.IO.Stream stream, long inLength)
{
base.magicByte = (byte)BlockSize.FOURBIT;
if (base.Supports(stream, inLength))
return true;
base.magicByte = (byte)BlockSize.EIGHTBIT;
return base.Supports(stream, inLength);
}
public override void Decompress(Stream instream, long inLength, Stream outstream)
{
#region GBATEK format specification
/*
Data Header (32bit)
Bit0-3 Data size in bit units (normally 4 or 8)
Bit4-7 Compressed type (must be 2 for Huffman)
Bit8-31 24bit size of decompressed data in bytes
Tree Size (8bit)
Bit0-7 Size of Tree Table/2-1 (ie. Offset to Compressed Bitstream)
Tree Table (list of 8bit nodes, starting with the root node)
Root Node and Non-Data-Child Nodes are:
Bit0-5 Offset to next child node,
Next child node0 is at (CurrentAddr AND NOT 1)+Offset*2+2
Next child node1 is at (CurrentAddr AND NOT 1)+Offset*2+2+1
Bit6 Node1 End Flag (1=Next child node is data)
Bit7 Node0 End Flag (1=Next child node is data)
Data nodes are (when End Flag was set in parent node):
Bit0-7 Data (upper bits should be zero if Data Size is less than 8)
Compressed Bitstream (stored in units of 32bits)
Bit0-31 Node Bits (Bit31=First Bit) (0=Node0, 1=Node1)
*/
#endregion
long readBytes = 0;
byte type = (byte)instream.ReadByte();
BlockSize blockSize = BlockSize.FOURBIT;
if (type != (byte)blockSize)
blockSize = BlockSize.EIGHTBIT;
if (type != (byte)blockSize)
throw new InvalidDataException("The provided stream is not a valid Huffman "
+ "compressed stream (invalid type 0x" + type.ToString("X") + "); unknown block size.");
byte[] sizeBytes = new byte[3];
instream.Read(sizeBytes, 0, 3);
int decompressedSize = base.Bytes2Size(sizeBytes);
readBytes += 4;
if (decompressedSize == 0)
{
sizeBytes = new byte[4];
instream.Read(sizeBytes, 0, 4);
decompressedSize = base.Bytes2Size(sizeBytes);
readBytes += 4;
}
#region Read the Huff-tree
if (readBytes >= inLength)
throw new NotEnoughDataException(0, decompressedSize);
int treeSize = instream.ReadByte(); readBytes++;
if (treeSize < 0)
throw new InvalidDataException("The stream is too short to contain a Huffman tree.");
treeSize = (treeSize + 1) * 2;
if (readBytes + treeSize >= inLength)
throw new InvalidDataException("The Huffman tree is too large for the given input stream.");
long treeEnd = (instream.Position - 1) + treeSize;
// the relative offset may be 4 more (when the initial decompressed size is 0), but
// since it's relative that doesn't matter, especially when it only matters if
// the given value is odd or even.
HuffTreeNode rootNode = new HuffTreeNode(instream, false, 5, treeEnd);
readBytes += treeSize;
// re-position the stream after the tree (the stream is currently positioned after the root
// node, which is located at the start of the tree definition)
instream.Position = treeEnd;
#endregion
// the current u32 we are reading bits from.
uint data = 0;
// the amount of bits left to read from <data>
byte bitsLeft = 0;
// a cache used for writing when the block size is four bits
int cachedByte = -1;
// the current output size
int currentSize = 0;
HuffTreeNode currentNode = rootNode;
byte[] buffer = new byte[4];
while (currentSize < decompressedSize)
{
#region find the next reference to a data node
while (!currentNode.IsData)
{
// if there are no bits left to read in the data, get a new byte from the input
if (bitsLeft == 0)
{
if (readBytes >= inLength)
throw new NotEnoughDataException(currentSize, decompressedSize);
int nRead = instream.Read(buffer, 0, 4);
if (nRead < 4)
throw new StreamTooShortException();
readBytes += nRead;
data = BitConverter.ToUInt32(buffer, 0);
bitsLeft = 32;
}
// get the next bit
bitsLeft--;
bool nextIsOne = (data & (1 << bitsLeft)) > 0;
// go to the next node, the direction of the child depending on the value of the current/next bit
currentNode = nextIsOne ? currentNode.Child1 : currentNode.Child0;
}
#endregion
#region write the data in the current node (when possible)
switch (blockSize)
{
case BlockSize.EIGHTBIT:
{
// just copy the data if the block size is a full byte
outstream.WriteByte(currentNode.Data);
currentSize++;
break;
}
case BlockSize.FOURBIT:
{
// cache the first half of the data if the block size is a half byte
if (cachedByte < 0)
{
cachedByte = currentNode.Data << 4;
}
else
{
// if we already cached a half-byte, combine the two halves and write the full byte.
cachedByte |= currentNode.Data;
outstream.WriteByte((byte)cachedByte);
currentSize++;
// be sure to forget the two written half-bytes
cachedByte = -1;
}
break;
}
default:
throw new Exception("Unknown block size " + blockSize.ToString());
}
#endregion
// make sure to start over next round
currentNode = rootNode;
}
// the data is 4-byte aligned. Although very unlikely in this case (compressed bit blocks
// are always 4 bytes long, and the tree size is generally 4-byte aligned as well),
// skip any padding due to alignment.
if (readBytes % 4 != 0)
readBytes += 4 - (readBytes % 4);
if (readBytes < inLength)
throw new TooMuchInputException(readBytes, inLength);
}
public override int Compress(Stream instream, long inLength, Stream outstream)
{
throw new NotImplementedException();
}
/// <summary>
/// A single node in a Huffman tree.
/// </summary>
public class HuffTreeNode
{
/// <summary>
/// The data contained in this node. May not mean anything when <code>isData == false</code>
/// </summary>
private byte data;
/// <summary>
/// A flag indicating if this node has been filled.
/// </summary>
private bool isFilled;
/// <summary>
/// The data contained in this node. May not mean anything when <code>isData == false</code>.
/// Throws a NullReferenceException when this node has not been defined (ie: reference was outside the
/// bounds of the tree definition)
/// </summary>
public byte Data
{
get
{
if (!this.isFilled) throw new NullReferenceException("Reference to an undefined node in the huffman tree.");
return this.data;
}
}
/// <summary>
/// A flag indicating if this node contains data. If not, this is not a leaf node.
/// </summary>
private bool isData;
/// <summary>
/// Returns true if this node represents data.
/// </summary>
public bool IsData { get { return this.isData; } }
/// <summary>
/// The child of this node at side 0
/// </summary>
private HuffTreeNode child0;
/// <summary>
/// The child of this node at side 0
/// </summary>
public HuffTreeNode Child0 { get { return this.child0; } }
/// <summary>
/// The child of this node at side 1
/// </summary>
private HuffTreeNode child1;
/// <summary>
/// The child of this node at side 1
/// </summary>
public HuffTreeNode Child1 { get { return this.child1; } }
/// <summary>
/// Creates a new node in the Huffman tree.
/// </summary>
/// <param name="stream">The stream to read from. It is assumed that there is (at least)
/// one more byte available to read.</param>
/// <param name="isData">If this node is a data-node.</param>
/// <param name="relOffset">The offset of this node in the source data, relative to the start
/// of the compressed file.</param>
/// <param name="maxStreamPos">The indicated end of the huffman tree. If the stream is past
/// this position, the tree is invalid.</param>
public HuffTreeNode(Stream stream, bool isData, long relOffset, long maxStreamPos)
{
/*
Tree Table (list of 8bit nodes, starting with the root node)
Root Node and Non-Data-Child Nodes are:
Bit0-5 Offset to next child node,
Next child node0 is at (CurrentAddr AND NOT 1)+Offset*2+2
Next child node1 is at (CurrentAddr AND NOT 1)+Offset*2+2+1
Bit6 Node1 End Flag (1=Next child node is data)
Bit7 Node0 End Flag (1=Next child node is data)
Data nodes are (when End Flag was set in parent node):
Bit0-7 Data (upper bits should be zero if Data Size is less than 8)
*/
if (stream.Position >= maxStreamPos)
{
// this happens when part of the tree is unused.
this.isFilled = false;
return;
}
this.isFilled = true;
int readData = stream.ReadByte();
if (readData < 0)
throw new StreamTooShortException();
this.data = (byte)readData;
this.isData = isData;
if (!this.isData)
{
int offset = this.data & 0x3F;
bool zeroIsData = (this.data & 0x80) > 0;
bool oneIsData = (this.data & 0x40) > 0;
// off AND NOT 1 == off XOR (off AND 1)
long zeroRelOffset = (relOffset ^ (relOffset & 1)) + offset * 2 + 2;
long currStreamPos = stream.Position;
// position the stream right before the 0-node
stream.Position += (zeroRelOffset - relOffset) - 1;
// read the 0-node
this.child0 = new HuffTreeNode(stream, zeroIsData, zeroRelOffset, maxStreamPos);
// the 1-node is directly behind the 0-node
this.child1 = new HuffTreeNode(stream, oneIsData, zeroRelOffset + 1, maxStreamPos);
// reset the stream position to right behind this node's data
stream.Position = currStreamPos;
}
}
public override string ToString()
{
if (this.isData)
{
return "<" + this.data.ToString("X2") + ">";
}
else
{
return "[" + this.child0.ToString() + "," + this.child1.ToString() + "]";
}
}
}
}
}