public OrderedLinkedList <TreeNode <CharacterFrequency> > TransferListToTree(OrderedLinkedList <TreeNode <CharacterFrequency> > orderedNodeList)
{
while (orderedNodeList.Count != 1)
{
TreeNode <CharacterFrequency> least = orderedNodeList.GetFirst();
orderedNodeList.RemoveFirst();
TreeNode <CharacterFrequency> nextLeast = orderedNodeList.GetFirst();
orderedNodeList.RemoveFirst();
TreeNode <CharacterFrequency> combinedLeast = new TreeNode <CharacterFrequency>(new CharacterFrequency('\0', (least.Element.Frequency + nextLeast.Element.Frequency)));
combinedLeast.Left = least;
combinedLeast.Right = nextLeast;
orderedNodeList.Add(combinedLeast);
}
return(orderedNodeList);
}
//Method used for compressing files
static void Compress(string input, string output)
{
//start of method
//Initilize variables
int totalChars = 0; //Counts number of characters in file, used for decompression purposes
BinaryTree <CharacterFrequency> charTree = new BinaryTree <CharacterFrequency>();
StreamReader read = new StreamReader(input);
//Create a dictionary of CharacterFrequency objects with the int key being the ascii code of each character
IDictionary <int, CharacterFrequency> charDictionary = new Dictionary <int, CharacterFrequency>();
//Read entire file character by character...
while (!read.EndOfStream)
{
int i = read.Read();
//checks if Dictionary contains the char i...
if (!charDictionary.ContainsKey(i))
{
//if not add new record to dictionary
charDictionary.Add(i, new CharacterFrequency((char)i, 1));
}
else
{
//if so increment the frequency of this record
charDictionary[i].increment();
}
totalChars++;
}
read.Close();
//Create ordered linked list of TreeNode<CharacterFrequency> objects
OrderedLinkedList <TreeNode <CharacterFrequency> > orderedNodeList = new OrderedLinkedList <TreeNode <CharacterFrequency> >();
//Go throughs each KeyValuePair in the CharacterFrequency dicitionary..
foreach (KeyValuePair <int, CharacterFrequency> c in charDictionary)
{
//Make a new TreeNode of the CharacterFrequency value from c...
TreeNode <CharacterFrequency> node = new TreeNode <CharacterFrequency>(c.Value);
//add into the ordered linked list of TreeNode<CharacterFrequency>
orderedNodeList.Add(node);
}
//Run a method in the binary tree to convert the ordered node list into a single node with branching children container all other nodes
//and return and set said node as the root node of the tree
charTree.Insert(charTree.TransferListToTree(orderedNodeList).GetFirst(), Relative.Root);
//Run a method from the tree to return a list of BinaryPath objects
LinkedList <BinaryPath <CharacterFrequency> > binaryTable = charTree.BinaryTable(charTree.Root);
//Removes all nodes from the binarytable that have a null character as they cannot show up in a file
var binary = binaryTable.First;
while (binary != null)
{
var nextNode = binary.Next;
if (binary.Value.Element.Character == '\0')
{
binaryTable.Remove(binary);
}
binary = nextNode;
}
//Byte writing section
int bitPosition = 7; //creates an int that determines what bit in the byte to set
byte y = 0; //creates the byte to set and write with
BinaryWriter binaryWriter = null;
bool error = true;
while (error)
{
try
{
binaryWriter = new BinaryWriter(File.Create(CheckFile(output)));
error = false;
}
catch (UnauthorizedAccessException ex)
{
MessageBox.Show("You do not have the permissions needed to write to this folder");
}
}
StreamReader streamReader = new StreamReader(input);
//string of the entire table, to used to append to the beginning of the output file. Will be read by out in decompression process
string tableText = String.Empty;
//Take the total characters from the input file and append to the beginning of the output file
tableText += totalChars + "~~~";
//Take table and write to output file
foreach (BinaryPath <CharacterFrequency> bp in binaryTable)
{
tableText += bp.Element.Character + bp.Path + ";";
}
binaryWriter.Write(tableText);
//Compression process
while (!streamReader.EndOfStream)
{
//Read each character from file..
int i = streamReader.Read();
//Find path of character from binary table...
string path = binaryTable.FirstOrDefault(obj => obj.Element.Character == (char)i).Path;
//Iterate through each character in path...
foreach (char c in path)
{
//If bitposition = 0 we have set all other bits
if (bitPosition == 0)
{
//if character is '1' set bit at bitposition in byte to 1 using bitwise OR(|)
if (c == '1')
{
y = (byte)(y | (byte)Math.Pow(2, bitPosition));
}
//Writes byte to output file
binaryWriter.Write(y);
//Resets byte and bitposition
y = 0;
bitPosition = 7;
}
//If bitposition != 0
else
{
//if character is '1' set bit at bitposition in byte to 1 using bitwise OR(|)
if (c == '1')
{
y = (byte)(y | (byte)Math.Pow(2, bitPosition));
}
//progresses bitposition down 1 to next bit in byte
bitPosition--;
}
}
}
//Close stream reader
read.Close();
//write final byte to output file and close BinaryWriter
binaryWriter.Write(y);
binaryWriter.Close();
//Output to command prompt to let user know file is finished being compressied, end program
Console.WriteLine($"File has been compressed to the file {output}");
}