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C#: implemented Huffman compression for both 4-bit and 8-bit block sizes. It will not result in compressed files identical to those found in games, as I'm currently not in the mood to figure out exactly what heuristic they use to build the Huffman tree.

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barubary 2011-05-15 11:40:14 +00:00
parent 99366a7a9a
commit 591c44b309
3 changed files with 346 additions and 22 deletions
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342
CSharp/DSDecmp/Formats/Nitro/Huffman.cs
View File

@ -35,6 +35,7 @@ namespace DSDecmp.Formats.Nitro
return base.Supports(stream, inLength);
}
#region Decompression method
public override long Decompress(Stream instream, long inLength, Stream outstream)
{
#region GBATEK format specification
@ -139,7 +140,7 @@ namespace DSDecmp.Formats.Nitro
}
// get the next bit
bitsLeft--;
bool nextIsOne = (data & (1 << bitsLeft)) > 0;
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;
}
@ -178,6 +179,8 @@ namespace DSDecmp.Formats.Nitro
}
#endregion
outstream.Flush();
// make sure to start over next round
currentNode = rootNode;
}
@ -190,24 +193,190 @@ namespace DSDecmp.Formats.Nitro
if (readBytes < inLength)
{
// the input may be 4-byte aligned.
if ((readBytes ^ (readBytes & 3)) + 4 < inLength)
throw new TooMuchInputException(readBytes, inLength);
throw new TooMuchInputException(readBytes, inLength);
}
return decompressedSize;
}
#endregion
public override int Compress(Stream instream, long inLength, Stream outstream)
{
switch (CompressBlockSize)
{
case BlockSize.FOURBIT:
return Compress4(instream, inLength, outstream);
case BlockSize.EIGHTBIT:
return Compress8(instream, inLength, outstream);
default:
throw new Exception("Unhandled BlockSize " + CompressBlockSize);
}
return 0;
}
#region 4-bit block size Compression method
/// <summary>
/// Applies Huffman compression with a datablock size of 4 bits.
/// </summary>
/// <param name="instream">The stream to compress.</param>
/// <param name="inLength">The length of the input stream.</param>
/// <param name="outstream">The stream to write the decompressed data to.</param>
/// <returns>The size of the decompressed data.</returns>
private int Compress4(Stream instream, long inLength, Stream outstream)
{
if (inLength > 0xFFFFFF)
throw new InputTooLargeException();
// cache the input, as we need to build a frequency table
byte[] inputData = new byte[inLength];
instream.Read(inputData, 0, (int)inLength);
// build that frequency table.
int[] frequencies = new int[0x10];
for (int i = 0; i < inLength; i++)
{
frequencies[inputData[i] & 0xF]++;
frequencies[(inputData[i] >> 4) & 0xF]++;
}
#region Build the Huffman tree
SimpleReversedPrioQueue<int, HuffTreeNode> leafQueue = new SimpleReversedPrioQueue<int, HuffTreeNode>();
SimpleReversedPrioQueue<int, HuffTreeNode> nodeQueue = new SimpleReversedPrioQueue<int, HuffTreeNode>();
int nodeCount = 0;
// make all leaf nodes, and put them in the leaf queue. Also save them for later use.
HuffTreeNode[] leaves = new HuffTreeNode[0x10];
for (int i = 0; i < 0x10; i++)
{
// there is no need to store leaves that are not used
if (frequencies[i] == 0)
continue;
HuffTreeNode node = new HuffTreeNode((byte)i, true, null, null);
leaves[i] = node;
leafQueue.Enqueue(frequencies[i], node);
nodeCount++;
}
while (leafQueue.Count + nodeQueue.Count > 1)
{
// get the two nodes with the lowest priority.
HuffTreeNode one = null, two = null;
int onePrio, twoPrio;
one = GetLowest(leafQueue, nodeQueue, out onePrio);
two = GetLowest(leafQueue, nodeQueue, out twoPrio);
// give those two a common parent, and put that node in the node queue
HuffTreeNode newNode = new HuffTreeNode(0, false, one, two);
nodeQueue.Enqueue(onePrio + twoPrio, newNode);
nodeCount++;
}
int rootPrio;
HuffTreeNode root = nodeQueue.Dequeue(out rootPrio);
// set the depth of all nodes in the tree, such that we know for each leaf how long
// its codeword is.
root.Depth = 0;
#endregion
// now that we have a tree, we can write that tree and follow with the data.
// write the compression header first
outstream.WriteByte((byte)BlockSize.FOURBIT); // this is block size 4 only
outstream.WriteByte((byte)(inLength & 0xFF));
outstream.WriteByte((byte)((inLength >> 8) & 0xFF));
outstream.WriteByte((byte)((inLength >> 16) & 0xFF));
int compressedLength = 4;
#region write the tree
outstream.WriteByte((byte)((nodeCount - 1) / 2));
compressedLength++;
// use a breadth-first traversal to store the tree, such that we do not need to store/calculate the side of each sub-tree.
LinkedList<HuffTreeNode> printQueue = new LinkedList<HuffTreeNode>();
printQueue.AddLast(root);
while (printQueue.Count > 0)
{
HuffTreeNode node = printQueue.First.Value;
printQueue.RemoveFirst();
if (node.IsData)
{
outstream.WriteByte(node.Data);
}
else
{
// bits 0-5: 'offset' = # nodes in queue left
// bit 6: node1 end flag
// bit 7: node0 end flag
byte data = (byte)(printQueue.Count / 2);
data = (byte)(data & 0x3F);
if (node.Child0.IsData)
data |= 0x80;
if (node.Child1.IsData)
data |= 0x40;
outstream.WriteByte(data);
printQueue.AddLast(node.Child0);
printQueue.AddLast(node.Child1);
}
compressedLength++;
}
#endregion
#region write the data
// the codewords are stored in blocks of 32 bits
uint datablock = 0;
byte bitsLeftToWrite = 32;
for (int i = 0; i < inLength; i++)
{
byte data = inputData[i];
for (int j = 0; j < 2; j++)
{
HuffTreeNode node = leaves[(data >> (4 - j * 4)) & 0xF];
// the depth of the node is the length of the codeword required to encode the byte
int depth = node.Depth;
bool[] path = new bool[depth];
for (int d = 0; d < depth; d++)
{
path[depth - d - 1] = node.IsChild1;
node = node.Parent;
}
for (int d = 0; d < depth; d++)
{
if (bitsLeftToWrite == 0)
{
outstream.Write(IOUtils.FromNDSu32(datablock), 0, 4);
compressedLength += 4;
datablock = 0;
bitsLeftToWrite = 32;
}
bitsLeftToWrite--;
if (path[d])
datablock |= (uint)(1 << bitsLeftToWrite);
// no need to OR the buffer with 0 if it is child0
}
}
}
// write the partly filled data block as well
if (bitsLeftToWrite != 32)
{
outstream.Write(IOUtils.FromNDSu32(datablock), 0, 4);
compressedLength += 4;
}
#endregion
return compressedLength;
}
#endregion
#region 8-bit block size Compression method
/// <summary>
/// Applies Huffman compression with a datablock size of 8 bits.
/// </summary>
@ -229,10 +398,12 @@ namespace DSDecmp.Formats.Nitro
for (int i = 0; i < inLength; i++)
frequencies[inputData[i]]++;
// build a Huffman tree from that frequency table
SimpleReversedPrioQueue<int, HuffTreeNode> prioQueue = new SimpleReversedPrioQueue<int, HuffTreeNode>();
#region Build the Huffman tree
// make all leaf nodes, and put them in the queue. Also save them for later use.
SimpleReversedPrioQueue<int, HuffTreeNode> leafQueue = new SimpleReversedPrioQueue<int, HuffTreeNode>();
SimpleReversedPrioQueue<int, HuffTreeNode> nodeQueue = new SimpleReversedPrioQueue<int, HuffTreeNode>();
int nodeCount = 0;
// make all leaf nodes, and put them in the leaf queue. Also save them for later use.
HuffTreeNode[] leaves = new HuffTreeNode[0x100];
for (int i = 0; i < 0x100; i++)
{
@ -241,29 +412,147 @@ namespace DSDecmp.Formats.Nitro
continue;
HuffTreeNode node = new HuffTreeNode((byte)i, true, null, null);
leaves[i] = node;
prioQueue.Enqueue(frequencies[i], node);
leafQueue.Enqueue(frequencies[i], node);
nodeCount++;
}
// combine the two nodes with the lowest total priority until
// there is only one left (the root node).
while (prioQueue.Count > 1)
while (leafQueue.Count + nodeQueue.Count > 1)
{
int prio0, prio1;
HuffTreeNode node0 = prioQueue.Dequeue(out prio0);
HuffTreeNode node1 = prioQueue.Dequeue(out prio1);
HuffTreeNode newNode = new HuffTreeNode(0, false, node0, node1);
prioQueue.Enqueue(prio0 + prio1, newNode);
// get the two nodes with the lowest priority.
HuffTreeNode one = null, two = null;
int onePrio, twoPrio;
one = GetLowest(leafQueue, nodeQueue, out onePrio);
two = GetLowest(leafQueue, nodeQueue, out twoPrio);
// give those two a common parent, and put that node in the node queue
HuffTreeNode newNode = new HuffTreeNode(0, false, one, two);
nodeQueue.Enqueue(onePrio + twoPrio, newNode);
nodeCount++;
}
int rootPrio;
HuffTreeNode root = prioQueue.Dequeue(out rootPrio);
HuffTreeNode root = nodeQueue.Dequeue(out rootPrio);
// set the depth of all nodes in the tree, such that we know for each leaf how long
// its codeword is.
root.Depth = 0;
#endregion
// now that we have a tree, we can write that tree and follow with the data.
return 0;
}
// write the compression header first
outstream.WriteByte((byte)BlockSize.EIGHTBIT); // this is block size 8 only
outstream.WriteByte((byte)(inLength & 0xFF));
outstream.WriteByte((byte)((inLength >> 8) & 0xFF));
outstream.WriteByte((byte)((inLength >> 16) & 0xFF));
int compressedLength = 4;
#region write the tree
outstream.WriteByte((byte)((nodeCount - 1) / 2));
compressedLength++;
// use a breadth-first traversal to store the tree, such that we do not need to store/calculate the side of each sub-tree.
LinkedList<HuffTreeNode> printQueue = new LinkedList<HuffTreeNode>();
printQueue.AddLast(root);
while (printQueue.Count > 0)
{
HuffTreeNode node = printQueue.First.Value;
printQueue.RemoveFirst();
if (node.IsData)
{
outstream.WriteByte(node.Data);
}
else
{
// bits 0-5: 'offset' = # nodes in queue left
// bit 6: node1 end flag
// bit 7: node0 end flag
byte data = (byte)(printQueue.Count / 2);
data = (byte)(data & 0x3F);
if (node.Child0.IsData)
data |= 0x80;
if (node.Child1.IsData)
data |= 0x40;
outstream.WriteByte(data);
printQueue.AddLast(node.Child0);
printQueue.AddLast(node.Child1);
}
compressedLength++;
}
#endregion
#region write the data
// the codewords are stored in blocks of 32 bits
uint datablock = 0;
byte bitsLeftToWrite = 32;
for (int i = 0; i < inLength; i++)
{
byte data = inputData[i];
HuffTreeNode node = leaves[data];
// the depth of the node is the length of the codeword required to encode the byte
int depth = node.Depth;
bool[] path = new bool[depth];
for (int d = 0; d < depth; d++)
{
path[depth - d - 1] = node.IsChild1;
node = node.Parent;
}
for (int d = 0; d < depth; d++)
{
if (bitsLeftToWrite == 0)
{
outstream.Write(IOUtils.FromNDSu32(datablock), 0, 4);
compressedLength += 4;
datablock = 0;
bitsLeftToWrite = 32;
}
bitsLeftToWrite--;
if (path[d])
datablock |= (uint)(1 << bitsLeftToWrite);
// no need to OR the buffer with 0 if it is child0
}
}
// write the partly filled data block as well
if (bitsLeftToWrite != 32)
{
outstream.Write(IOUtils.FromNDSu32(datablock), 0, 4);
compressedLength += 4;
}
#endregion
return compressedLength;
}
#endregion
/// <summary>
/// Gets the tree node with the lowest priority (frequency) from the leaf and node queues.
/// If the priority is the same for both head items in the queues, the node from the leaf queue is picked.
/// </summary>
private HuffTreeNode GetLowest(SimpleReversedPrioQueue<int, HuffTreeNode> leafQueue, SimpleReversedPrioQueue<int, HuffTreeNode> nodeQueue, out int prio)
{
if (leafQueue.Count == 0)
return nodeQueue.Dequeue(out prio);
else if (nodeQueue.Count == 0)
return leafQueue.Dequeue(out prio);
else
{
int leafPrio, nodePrio;
leafQueue.Peek(out leafPrio);
nodeQueue.Peek(out nodePrio);
// pick a node from the leaf queue when the priorities are equal.
if (leafPrio <= nodePrio)
return leafQueue.Dequeue(out prio);
else
return nodeQueue.Dequeue(out prio);
}
}
#region Utility class: HuffTreeNode
/// <summary>
@ -321,6 +610,14 @@ namespace DSDecmp.Formats.Nitro
/// The parent node of this node.
/// </summary>
public HuffTreeNode Parent { get; private set; }
/// <summary>
/// Determines if this is the Child0 of the parent node. Assumes there is a parent.
/// </summary>
public bool IsChild0 { get { return this.Parent.child0 == this; } }
/// <summary>
/// Determines if this is the Child1 of the parent node. Assumes there is a parent.
/// </summary>
public bool IsChild1 { get { return this.Parent.child1 == this; } }
private int depth;
/// <summary>
@ -356,10 +653,11 @@ namespace DSDecmp.Formats.Nitro
this.child0 = child0;
this.child1 = child1;
this.isFilled = true;
if (child0 != null)
if (!isData)
{
this.child0.Parent = this;
if (child1 != null)
this.child1.Parent = this;
}
}
/// <summary>

14
CSharp/DSDecmp/Utils/IOUtils.cs
View File

@ -23,5 +23,19 @@ namespace DSDecmp
| (buffer[offset + 2] << 16)
| (buffer[offset + 3] << 24));
}
/// <summary>
/// Converts a u32 value into a sequence of bytes that would make ToNDSu32 return
/// the given input value.
/// </summary>
public static byte[] FromNDSu32(uint value)
{
return new byte[] {
(byte)(value & 0xFF),
(byte)((value >> 8) & 0xFF),
(byte)((value >> 16) & 0xFF),
(byte)((value >> 24) & 0xFF)
};
}
}
}

12
CSharp/DSDecmp/Utils/SimpleReversePrioQueue.cs
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@ -33,6 +33,18 @@ namespace DSDecmp.Utils
this.itemCount++;
}
public TValue Peek(out TPrio priority)
{
if (this.itemCount == 0)
throw new IndexOutOfRangeException();
foreach (KeyValuePair<TPrio, LinkedList<TValue>> kvp in this.items)
{
priority = kvp.Key;
return kvp.Value.First.Value;
}
throw new IndexOutOfRangeException();
}
public TValue Dequeue(out TPrio priority)
{
if (this.itemCount == 0)