public int getChar(BitStream s)
{
HuffNode n = root;
long bit;
int ch;
// find the leaf node:
while (n.character == innode)
{
bit = s.ReadBits(1);
n = ((bit & 1) != 0) ? n.right : n.left;
}
if (n.character == NYT)
{
// if the leaf is NYT, read the next character:
ch = (int)s.ReadBits(codeSize);
splitNYT(ch);
n = leaves[ch].parent;
}
else
{
ch = n.character;
}
// update the tree:
rearrangeTree(n);
return(ch);
}
private void splitNYT(int character)
{
HuffNode n1, n2;
n1 = new HuffNode(NYT);
n2 = new HuffNode(character);
leaves[NYT].character = innode;
leaves[NYT].freq = 1;
// siblings:
n1.next = n2;
n2.next = leaves[NYT];
n2.prev = n1;
leaves[NYT].prev = n2;
// tree links:
n1.parent = leaves[NYT];
n2.parent = leaves[NYT];
leaves[NYT].left = n1;
leaves[NYT].right = n2;
// update leaf node:
leaves[NYT] = n1;
leaves[character] = n2;
}
public void init(int maxSymbol)
{
if (wordCount != maxSymbol + 2)
{
wordCount = maxSymbol + 2; // including NYT
NYT = maxSymbol + 1;
innode = maxSymbol + 2;
// compute code-word size:
codeSize = 1;
int size = 2;
while (size < NYT)
{
size += size;
codeSize++;
}
// array of leaves:
leaves = new HuffNode[wordCount];
}
else
{
for (int i = 0; i < wordCount;)
{
leaves[i] = null;
}
}
// root item:
root = new HuffNode(NYT);
leaves[NYT] = root;
}
private void writeCode(HuffNode node, BitStream s)
{
if (node == root)
{
return;
}
writeCode(node.parent, s);
s.WriteBits((node.parent.left == node) ? 0 : 1, 1);
}
private void rearrangeTree(HuffNode node)
{
while (node != root)
{
node = swapLast(node);
node.freq++;
node = node.parent;
}
node.freq++;
}
private void printTreeInner(HuffNode node)
{
if (node == null)
{
return;
}
printTreeInner(node.left);
printTreeInner(node.right);
}
/// <summary>
/// Builds tree.
/// </summary>
/// <param name="source"></param>
public void Build(byte[] source)
{
Frequencies = new Dictionary <byte, int>();
for (int i = 0; i < source.Length; i++)
{
if (!Frequencies.ContainsKey(source[i]))
{
//table.Add(source[i], 0);
Frequencies.Add(source[i], 0);
//ary.Add(new KeyValuePair<byte, int>(source[i],0));
}
Frequencies[source[i]]++;
//int temp = ary.ElementAt(i).Value;
//ary.RemoveAt(i);
//ary.Insert(i, new KeyValuePair<byte, int>(source[i],++temp));
//int temp = (int)table[source[i]];
//table.Remove(source[i]);
//table.Add(source[i], +temp);
}
foreach (KeyValuePair <byte, int> symbol in Frequencies)
{
nodes.Add(new HuffNode()
{
Symbol = symbol.Key, Frequency = symbol.Value
});
}
while (nodes.Count > 1)
{
List <HuffNode> orderedNodes = nodes.OrderBy(node => node.Frequency).ToList <HuffNode>();
if (orderedNodes.Count >= 2)
{
// Take first two items
List <HuffNode> taken = orderedNodes.Take(2).ToList <HuffNode>();
// Create a parent node by combining the frequencies
HuffNode parent = new HuffNode()
{
Symbol = (byte)'*',
Frequency = taken[0].Frequency + taken[1].Frequency,
Left = taken[0],
Right = taken[1]
};
nodes.Remove(taken[0]);
nodes.Remove(taken[1]);
nodes.Add(parent);
}
this.Root = nodes.FirstOrDefault();
}
}
public byte[] Decode(BitArray bits)
{
int[] size = { 0 };
ExtractFront(bits, sizeof(int) * 8).CopyTo(size, 0);
bits = ExtractEnd(bits, bits.Length - sizeof(int) * 8);//bits is bits - size
MemoryStream ms = new MemoryStream();
Frequencies = new Dictionary <byte, int>();
for (int i = 0; i < size[0]; i++)
{
BitArray freq = ExtractFront(bits, sizeof(byte) * 8);//
byte[] key = { 0 };
freq.CopyTo(key, 0);
bits = ExtractEnd(bits, bits.Length - sizeof(byte) * 8);
freq = ExtractFront(bits, sizeof(int) * 8);
int[] value = { 0 };
freq.CopyTo(value, 0);
bits = ExtractEnd(bits, bits.Length - sizeof(int) * 8);
Frequencies.Add(key[0], value[0]);
}
Build();
//Frequencies = (Dictionary<byte, int>)bs.Deserialize(ms);
HuffNode current = this.Root;
List <byte> decoded = new List <byte>();
foreach (bool bit in bits)
{
if (bit)
{
if (current.Right != null)
{
current = current.Right;
}
}
else
{
if (current.Left != null)
{
current = current.Left;
}
}
if (IsLeaf(current))
{
decoded.Add(current.Symbol);
current = this.Root;
}
}
return(decoded.ToArray());
}
/// <summary>
/// Builds tree with already constructed frequencies table.
/// </summary>
public void Build()
{
foreach (KeyValuePair <byte, int> symbol in Frequencies)
{
nodes.Add(new HuffNode()
{
Symbol = symbol.Key,
Frequency = symbol.Value
});
}
while (nodes.Count > 1)
{
List <HuffNode> orderedNodes = nodes.OrderBy(node => node.Frequency).ToList <HuffNode>();
if (orderedNodes.Count >= 2)
{
// Take first two items
List <HuffNode> taken = orderedNodes.Take(2).ToList <HuffNode>();
// Create a parent node by combining the frequencies
HuffNode parent = new HuffNode()
{
Symbol = (byte)'*',
Frequency = taken[0].Frequency + taken[1].Frequency,
Left = taken[0],
Right = taken[1]
};
nodes.Remove(taken[0]);
nodes.Remove(taken[1]);
nodes.Add(parent);
}
this.Root = nodes.FirstOrDefault();
}
}
/// <summary>
/// Check if node is a leaf node.
/// </summary>
/// <param name="node"></param>
/// <returns></returns>
public bool IsLeaf(HuffNode node)
{
return(node.Left == null && node.Right == null);
}
private HuffNode swapLast(HuffNode node)
{
HuffNode n;
// find the last node with the same frequency..
n = node;
while (n.next != null &&
n.next != root &&
n.next.freq == node.freq)
{
n = n.next;
}
// it's me and my parent => dont swap
if (n == node)
{
return(node);
}
// swap data:
int d = node.character;
node.character = n.character;
n.character = d;
long f = node.freq;
node.freq = n.freq;
n.freq = f;
// swap children:
HuffNode h;
h = node.left;
node.left = n.left;
n.left = h;
h = node.right;
node.right = n.right;
n.right = h;
if (node.character == innode)
{
node.left.parent = node;
node.right.parent = node;
}
if (n.character == innode)
{
n.left.parent = n;
n.right.parent = n;
}
// update list of leaves:
if (node.character != innode)
{
leaves[node.character] = node;
}
if (n.character != innode)
{
leaves[n.character] = n;
}
return(n);
}