// This method decodes bytes into a string, based on the current huffman tree
// Essentially, the opposite of the one above
public string Decode(byte[] encoded)
{
// Turn the bytes into bits, and make a list of them
BitList bits = BitList.Parse(new BitArray(encoded));
// a recursive function to remove the ending of the bits
// the ending is there, only to make sure that the length of the list is divisible by 8
// this function therefore removes 0 from the end, until it hits a 1, which is then removed, and the function stops
void clean(BitList list)
{
//if it is a 1
if (list[list.Count - 1])
{
//remove the 1
list.RemoveAt(list.Count - 1);
}
// if it is a 0
else
{
//remove the 0
list.RemoveAt(list.Count - 1);
//repeat
clean(list);
}
}
//call the function just described
clean(bits);
//init the string that is going to hold the decoded string
string str = "";
//define a variable to hold the current node that we are on
HuffmanNode currentNode = Root;
//loop thought all the bits
for (int i = 0; i < bits.Count; i++)
{
//if it is a 1, take the right node
if (bits[i])
{
currentNode = currentNode.RightChildNode;
}
//if it is a 0, take the left node
else
{
currentNode = currentNode.LeftChildNode;
}
// if the current node is a leaf
if (currentNode.IsLeaf)
{
// add the symbol to the str variable
str += currentNode.Symbol;
// go back to the root of the tree
currentNode = Root;
}
}
;
// return the decoded symbols
return(str);
}
// this method creates a tree based on text
// Denne funktion laver et træ baseret på tekst
public static HuffmanTree CreateFromText(string text)
{
// the list that we wanna fill up with nodes
// Listen der skal fyldes med noder
List <HuffmanNode> nodeList = new List <HuffmanNode>();
// all the characters from the text
// Alle symbolerne fra teksten
char[] characters = text.ToCharArray();
// loop thought the characters
// Gentag igennem symbolerne
for (int i = 0; i < characters.Length; i++)
{
// the character as a string
// Symbolerne som strenge
string read = characters[i].ToString();
// has the node already been created?
// Er noden allerede blevet skabt?
if (nodeList.Exists(x => x.Symbol == read))
{
// If is yes, find the index of the Node and increase the frequency of the Node.
// Hvis ja, find indekset for noden og øg frekvensen for node
nodeList[nodeList.FindIndex(y => y.Symbol == read)].Frequency++;
}
else
{
// If is no, create a new node and add to the List of Nodes
// Hvis nej, skab en ny node og tilføj den til listen over node
nodeList.Add(new HuffmanNode(read));
}
}
// sort them, this is done based on frequency because of IComparable<HuffmanNode>.CompareTo
// Sorter dem, dette gøres baseret på frekvens fordi at IComparable<HuffmanNode>.CompareTo
nodeList.Sort();
// loop thought them, until only one is left
// Kør igennem dem alle sammen indtil der kun er en tilbage
while (nodeList.Count > 1)
{
// Get the node of the first index of List, this is the one with the lowest frequency
// Få noden for det første indeks af Listen, dette er den med den laveste frekvens
HuffmanNode node1 = nodeList[0];
// and delete it.
// Fjern den
nodeList.RemoveAt(0);
// do the same thing again
// Gør det samme igen
HuffmanNode node2 = nodeList[0];
nodeList.RemoveAt(0);
// make a parant node with node1 and node2 and the left and right child nodes
// Lav en parent-node med node1 og node1 og de venstre og højre child-noder
nodeList.Add(new HuffmanNode(node1, node2));
// and sort it again according to frequency.
// Og sorter det igen efter frekvens
nodeList.Sort();
}
// create a tree based on the remaining root node
// Lav et træ baseret på den tilbageværende rod-node
HuffmanTree tree = new HuffmanTree(nodeList[0]);
// this is a recursive function to set the binary code of every leaf node
// Dette er en rekursiv funktion for at sætte den binære værdi for hvert blad
void setCodeToTheTree(HuffmanNode Nodes, BitArray code = null)
{
// if the current code is not set, set it to an empty BitArray
// Hvis den nuværende kode ikke er sat, sættes den til et tomt BitArray
if (code == null)
{
code = new BitArray(new bool[] { });
}
// if the code is empty do nothing
// Hvis koden er tom, gør intet
if (Nodes == null)
{
return;
}
// if there is no left node and right node, then set the code based on the current code
// Hvis der ikke er nogen venstre node, sæt koden baseret på den nuværende kode
if (Nodes.LeftChildNode == null && Nodes.RightChildNode == null)
{
Nodes.Code = code;
return;
}
// create a bitlist for the left node
// lav en bitliste for den venstre node
BitList left = BitList.Parse(code);
// add false for the left side
// tilføj false for den venstre side
left.Add(false);
// call this function recursively, with the left bitlist and the left side node
// Kald denne funktion rekursivt, med den venstre bitliste og den venstre node
setCodeToTheTree(Nodes.LeftChildNode, left.ToBitArray());
// create a bitlist for the right node
// Lav en bitliste for den højre node
BitList right = BitList.Parse(code);
// add true for the right side
// tilføj true for den højre side
right.Add(true);
// call the function recursively, with the right bitlist and the right side node
// Kald denne funktion rekursivt, med den højre bitliste og den højre node
setCodeToTheTree(Nodes.RightChildNode, right.ToBitArray());
}
// call the recursive function
// Kald den rekursive funktion
setCodeToTheTree(tree.Root);
// the tree
// Træet returneres
return(tree);
}
// this method creates a tree based on text
public static HuffmanTree CreateFromText(string text)
{
// the list that we wanna fill up with nodes
List <HuffmanNode> nodeList = new List <HuffmanNode>();
// all the characters from the text
char[] characters = text.ToCharArray();
// loop thought the characters
for (int i = 0; i < characters.Length; i++)
{
// the character as a string
string read = characters[i].ToString();
// has the node already been created?
if (nodeList.Exists(x => x.Symbol == read))
{
// If is yes, find the index of the Node and increase the frequency of the Node.
nodeList[nodeList.FindIndex(y => y.Symbol == read)].Frequency++;
}
else
{
// If is no, create a new node and add to the List of Nodes
nodeList.Add(new HuffmanNode(read));
}
}
// sort them, this is done based on frequency because of IComparable<HuffmanNode>.CompareTo
nodeList.Sort();
// loop thought them, until only one is left
while (nodeList.Count > 1)
{
// Get the node of the first index of List, this is the one with the lowest frequency
HuffmanNode node1 = nodeList[0];
// and delete it.
nodeList.RemoveAt(0);
// do the same thing again
HuffmanNode node2 = nodeList[0];
nodeList.RemoveAt(0);
// make a parant node with node1 and node2 and the left and right child nodes
nodeList.Add(new HuffmanNode(node1, node2));
// and sort it again according to frequency.
nodeList.Sort();
}
// create a tree based on the remaining root node
HuffmanTree tree = new HuffmanTree(nodeList[0]);
// this is a recursive function to set the binary code of every leaf node
void setCodeToTheTree(HuffmanNode Nodes, BitArray code = null)
{
// if the current code is not set, set it to an empty BitArray
if (code == null)
{
code = new BitArray(new bool[] { });
}
// if the code is empty do nothing
if (Nodes == null)
{
return;
}
// if there is no left node and right node, then set the code based on the current code
if (Nodes.LeftChildNode == null && Nodes.RightChildNode == null)
{
Nodes.Code = code;
return;
}
// create a bitlist for the left node
BitList left = BitList.Parse(code);
// add false for the left side
left.Add(false);
// call this function recursively, with the left bitlist and the left side node
setCodeToTheTree(Nodes.LeftChildNode, left.ToBitArray());
// create a bitlist for the right node
BitList right = BitList.Parse(code);
// add true for the right side
right.Add(true);
// call the function recursively, with the right bitlist and the right side node
setCodeToTheTree(Nodes.RightChildNode, right.ToBitArray());
}
// call the recursive function
setCodeToTheTree(tree.Root);
// the tree
return(tree);
}
// This method decodes bytes into a string, based on the current huffman tree
// Essentially, the opposite of the one above
// Denne funktion afkoder bytes til en string, baseret på det nuværende Huffman-træ
// Stort set bare det foregående baglæns
public string Decode(byte[] encoded)
{
// Turn the bytes into bits, and make a list of them
// Bytes omdannes til bits, og der laves en liste af dem
BitList bits = BitList.Parse(new BitArray(encoded));
// a recursive function to remove the ending of the bits
// the ending is there, only to make sure that the length of the list is divisible by 8
// this function therefore removes 0 from the end, until it hits a 1, which is then removed, and the function stops
// En rekursiv funktion for at fjerne enderne på bits
// Enderne er der kun for at sikre at længden på listen kan divideres med 8
// Denne funktion fjerner derfor 0'er fra enden, indtil at den rammer et 1, hvilket derefter fjernes og funktionen stopper
void clean(BitList list)
{
//if it is a 1
// Hvis det er et 1
if (list[list.Count - 1])
{
// remove the 1
// Fjern 1
list.RemoveAt(list.Count - 1);
}
// if it is a 0
// Hvis det er et 0
else
{
// remove the 0
// Fjern 0
list.RemoveAt(list.Count - 1);
// repeat
// Gentag
clean(list);
}
}
// call the function just described
// Kald funktionen fra før
clean(bits);
// init the string that is going to hold the decoded string
// strengen der skal indehold den afkodede streng laves
string str = "";
// define a variable to hold the current node that we are on
// Der defineres en variabel til at holde det nuværende node der kigges på
HuffmanNode currentNode = Root;
// loop thought all the bits
// Kør igennem alle bits
for (int i = 0; i < bits.Count; i++)
{
// if it is a 1, take the right node
// Hvis det er et 1, tag højre node
if (bits[i])
{
currentNode = currentNode.RightChildNode;
}
// if it is a 0, take the left node
// Hvis det er et 0, tag venstre node
else
{
currentNode = currentNode.LeftChildNode;
}
// if the current node is a leaf
// Hvis den nuværende node er et blad
if (currentNode.IsLeaf)
{
// add the symbol to the str variable
// Tilføj symbolet til streng-variablen "str"
str += currentNode.Symbol;
// go back to the root of the tree
// Gå tilbage til træets rod
currentNode = Root;
}
}
;
// return the decoded symbols
// Returner de afkodede symboler
return(str);
}
