private void BuildNodes()
{
for (int i = 0; i <= 255; i++)
{
int currentOccurences = occurences[i];
HuffmanNode node = new HuffmanNode();
node.Data = (byte)i;
node.Occurrences = currentOccurences;
flatNodes.Add(node);
nodes.Add(node);
}
}
private byte[] HuffmanCompress(byte[] data)
{
for (int i = 0; i < data.Length; i++)
{
int current = data[i];
HuffmanNode node = (HuffmanNode)nodes[current];
WriteBits(node.BitMask, node.BitCount);
}
FlushByte();
stream.WriteByte((byte)bufferBytePos);
byte[] compressedBytes = new byte[stream.Length];
stream.Position = 0;
stream.Read(compressedBytes, 0, compressedBytes.Length);
return(compressedBytes);
}
public int Compare(object x, object y)
{
HuffmanNode a = (HuffmanNode)x;
HuffmanNode b = (HuffmanNode)y;
if (a.Occurrences == b.Occurrences)
{
return(0);
}
if (a.Occurrences > b.Occurrences)
{
return(1);
}
else
{
return(-1);
}
}
private void BuildNodeMask(HuffmanNode node, int lastMask, int bits)
{
if (node == null)
{
return;
}
if (node.Occurrences == 0)
{
return;
}
node.BitMask = (lastMask << 1) | node.Bit;
bits++;
node.BitCount = bits;
BuildNodeMask(node.LeftNode, node.BitMask, node.BitCount);
BuildNodeMask(node.RightNode, node.BitMask, node.BitCount);
}
private void BuildNodeTree()
{
while (flatNodes.Count > 1)
{
SortFlatNodes();
HuffmanNode a = flatNodes[0] as HuffmanNode;
HuffmanNode b = flatNodes[1] as HuffmanNode;
HuffmanNode c = new HuffmanNode();
c.IsLeaf = false;
c.Occurrences = a.Occurrences + b.Occurrences;
c.LeftNode = a;
c.RightNode = b;
a.Bit = 0;
b.Bit = 1;
flatNodes.RemoveAt(0);
flatNodes.RemoveAt(0);
flatNodes.Add(c);
}
rootNode = flatNodes[0] as HuffmanNode;
}
public byte[] Decompress(byte[] bytes)
{
nodes.Clear() ;
for (int i = 0 ; i < 256;i++)
{
int occurence = BitConverter.ToInt32(bytes,i*4);
occurences[i] = occurence;
}
nodes = new ArrayList() ;
flatNodes = new ArrayList() ;
rootNode = null;
BuildNodes();
BuildNodeTree();
BuildNodeMasks();
MemoryStream data = new MemoryStream(bytes,256*4,bytes.Length-256*4) ;
data.Position = data.Length-1;
int endBufferPos = data.ReadByte() ;
data.Position = 0;
MemoryStream result = new MemoryStream();
int bufferPos = -1;
int currentByte = 0;
HuffmanNode currentNode = null;
while (true)
{
while(true)
{
if (bufferPos == -1)
{
currentByte = data.ReadByte();
bufferPos = 7;
}
int bitmask = 1 << (bufferPos);
int currentBit = ((currentByte & bitmask) >> (bufferPos));
currentByte = currentByte & 255-bitmask;
bufferPos--;
if (currentNode == null)
currentNode = rootNode;
else if (currentBit == 0)
currentNode = currentNode.LeftNode;
else
currentNode = currentNode.RightNode;
if (currentNode.IsLeaf)
{
break;
}
}
result.WriteByte(currentNode.Data);
currentNode = null;
if (endBufferPos == 7)
endBufferPos = -1;
if (data.Position == data.Length-1 && bufferPos == endBufferPos)
break;
}
byte[] compressedBytes = new byte[result.Length] ;
result.Position = 0;
result.Read(compressedBytes,0,compressedBytes.Length);
return compressedBytes;
}
private void BuildNodeTree()
{
while (flatNodes.Count > 1)
{
SortFlatNodes ();
HuffmanNode a = flatNodes[0] as HuffmanNode;
HuffmanNode b = flatNodes[1] as HuffmanNode;
HuffmanNode c = new HuffmanNode() ;
c.IsLeaf = false;
c.Occurrences = a.Occurrences + b.Occurrences;
c.LeftNode = a;
c.RightNode = b;
a.Bit = 0;
b.Bit = 1;
flatNodes.RemoveAt(0) ;
flatNodes.RemoveAt(0) ;
flatNodes.Add(c);
}
rootNode = flatNodes[0] as HuffmanNode;
}
private void BuildNodes()
{
for (int i=0;i<=255;i++)
{
int currentOccurences = occurences[i];
HuffmanNode node = new HuffmanNode();
node.Data = (byte)i;
node.Occurrences = currentOccurences;
flatNodes.Add(node);
nodes.Add(node);
}
}
private void BuildNodeMask(HuffmanNode node,int lastMask,int bits)
{
if (node == null)
return;
if (node.Occurrences ==0)
return;
node.BitMask = (lastMask << 1) | node.Bit;
bits ++;
node.BitCount = bits;
BuildNodeMask (node.LeftNode,node.BitMask,node.BitCount);
BuildNodeMask (node.RightNode,node.BitMask,node.BitCount);
}
public byte[] Decompress(byte[] bytes)
{
nodes.Clear();
for (int i = 0; i < 256; i++)
{
int occurence = BitConverter.ToInt32(bytes, i * 4);
occurences[i] = occurence;
}
nodes = new ArrayList();
flatNodes = new ArrayList();
rootNode = null;
BuildNodes();
BuildNodeTree();
BuildNodeMasks();
MemoryStream data = new MemoryStream(bytes, 256 * 4, bytes.Length - 256 * 4);
data.Position = data.Length - 1;
int endBufferPos = data.ReadByte();
data.Position = 0;
MemoryStream result = new MemoryStream();
int bufferPos = -1;
int currentByte = 0;
HuffmanNode currentNode = null;
while (true)
{
while (true)
{
if (bufferPos == -1)
{
currentByte = data.ReadByte();
bufferPos = 7;
}
int bitmask = 1 << (bufferPos);
int currentBit = ((currentByte & bitmask) >> (bufferPos));
currentByte = currentByte & 255 - bitmask;
bufferPos--;
if (currentNode == null)
{
currentNode = rootNode;
}
else if (currentBit == 0)
{
currentNode = currentNode.LeftNode;
}
else
{
currentNode = currentNode.RightNode;
}
if (currentNode.IsLeaf)
{
break;
}
}
result.WriteByte(currentNode.Data);
currentNode = null;
if (endBufferPos == 7)
{
endBufferPos = -1;
}
if (data.Position == data.Length - 1 && bufferPos == endBufferPos)
{
break;
}
}
byte[] compressedBytes = new byte[result.Length];
result.Position = 0;
result.Read(compressedBytes, 0, compressedBytes.Length);
return(compressedBytes);
}
