public static HashTable<char, BitStream> MakeEncodingTable(Node node, BitStream progress)
{
HashTable<char,BitStream> result = new HashTable<char,BitStream>(char.MaxValue,HashChar);
//if the current node is not null and it is a leaf, we want to add it to result
if (node != null && node.Left == null && node.Right == null) {
//we only store leaf nodes in the result array
//make a new bit stream
BitStream stream = new BitStream();
//append progress to it
stream.Append(progress);
//add node.data and the new stream to result
result.Add(node.Data, stream);
}
//else if the node is not null, we are going to want to process it's childern
else {
if (node != null && node.Left != null) {
//if left subtree is not null
//make new bit stream
BitStream stream = new BitStream();
//append progress
stream.Append(progress);
//append 0 (because we are going left)
stream.Append(false);
//recursivley call this function on node.Left with the new stream we just created
//store the result of the previous call in a local hashtable
HashTable<char, BitStream> local = MakeEncodingTable(node.Left, stream);
//loop through the just created hash table(the return of the recursive function)
SLinkedList<char> list = local.Keys;
for (int i = 0; i < list.Size; i++) {
//add each key value pair to this function's result hash table
result.Add(list[i], local[list[i]]);
//we do this because the results of each recursion bubble back up to the top.
//by the time the root returns, all of the leaf nodes will be in the final hash table
}//end loop
}//end if
if (node != null && node.Right != null) {
//repeat above for the right subtree
BitStream stream = new BitStream();
stream.Append(progress);
stream.Append(true);
HashTable<char, BitStream> local = MakeEncodingTable(node.Right, stream);
SLinkedList<char> list = local.Keys;
for (int i = 0; i < list.Size; i++) {
result.Add(list[i], local[list[i]]);
}
}//end else
}
return result;
}
public void Append(BitStream stream)
{
// Cache stream size as a member variable. We do this because
int streamSize = stream.BitCount;
// it's valid to add elements mid loop. If we do this however,
// we will face an infinite loop if the stream passed in is the
// same stream we are writing to. To avoid this scenario, we need
// a 'Stream Size' to be recorded in a variable local to this function
// we loop on this integer, not stream.Size.
//(Inside the loop) Get every bit, and call the existing Append function
for (int i = 0; i < streamSize; i++) {
if (stream.BitAt(i)) {
Append(true);
}
else{
Append(false);
}
}
}
public static byte[] Compress(string toCompress)
{
//then at the end of the function we're going to convert it to an array, and return it.
Vector<byte> result = new Vector<byte>();
//make an encoding table out of the huffman tree, out of a frequency table
Console.WriteLine("Making Huffman frequency table");
HashTable<char, int> FreqTable = MakeFrequencyTable(toCompress); //copy to memory because we access it multiple times
Console.WriteLine("Making Huffman tree");
Node huffmanTree = MakeHuffmanTree(FreqTable);
Console.WriteLine("Making Huffman encoding table");
HashTable<char, BitStream> encodingTable = MakeEncodingTable(huffmanTree, new BitStream()); // add to memory because accessed twice
//convert the size of the frequency table to bytes.
Console.WriteLine("Converting to bytes");
byte[] freqToByte = IntToBytes(FreqTable.Size);
//and all four bytes to the resuld linked list
Console.WriteLine("Adding bytes bytes");
result.AddRange(freqToByte);
//next loop through the frequency table
SLinkedList<char> list = FreqTable.Keys;
Console.WriteLine("looping through frequency table");
for (int i = 0; i < list.Size; i++) {
//convert current key to two bytes
byte[] key = CharToBytes(list[i]);
//add both bytes to the linked list
result.AddRange(key);
//convert the current value to foure bytes,
byte[] value = IntToBytes(FreqTable[list[i]]);
//add alll four bytes to the linked list
result.AddRange(value);
}//end loop
//make new bitstream (datastream) to hold bits
BitStream datastream = new BitStream();
//loop through the string
Console.WriteLine("Looping through input and adding to datastream");
for (int i = 0; i < toCompress.Length; i++) {
//append the bitstream of the encoding table to the newely created bitstream
datastream.Append(encodingTable[toCompress[i]]);
}//end loop
//get the bit streams bit count as an integer
int streamBitCount = datastream.BitCount;
//convert this integer to bytes and add it to the result list
Console.WriteLine("Converting bytes");
byte[] streambitByte = IntToBytes(streamBitCount);
result.AddRange(streambitByte);
Console.WriteLine("Copying Bytes");
result.AddRange(datastream.Bytes);
//finally convert the result list to a byte array.
Console.WriteLine("Convert results list to byte array");
byte[] byteResult = result.ToArray();
//return the array
return byteResult;
}
public static void Main(string[] args)
{
BitStream stream = new BitStream ();
stream.Append (true);
stream.Append (true);
stream.Append (true);
string debug = stream.ToString ();
Console.WriteLine (debug);
if (debug != "111") {
Error ("Expecting 111, got " + debug);
Console.ReadLine();
return;
}
stream.Append (false);
stream.Append (true);
stream.Append (false);
stream.Append (false);
stream.Append (true);
debug = stream.ToString ();
Console.WriteLine (debug);
if (debug != "11101001") {
Error ("Expecting 11101001, got " + debug);
Console.ReadLine();
return;
}
Console.WriteLine ("0: " + stream.BitAt (0) + " / True");
if (!stream.BitAt (0)) {
Error ("Expecting bit 0 to be on, it was not");
Console.ReadLine();
return;
}
Console.WriteLine ("1: " + stream.BitAt (1) + " / True");
if (!stream.BitAt (1)) {
Error ("Expecting bit 1 to be on, it was not");
Console.ReadLine();
return;
}
Console.WriteLine ("2: " + stream.BitAt (2) + " / True");
if (!stream.BitAt (2)) {
Error ("Expecting bit 2 to be on, it was not");
Console.ReadLine();
return;
}
Console.WriteLine ("3: " + stream.BitAt (3) + " / False");
if (stream.BitAt (3)) {
Error ("Expecting bit 3 to be off, it was not");
Console.ReadLine();
return;
}
Console.WriteLine ("4: " + stream.BitAt (4) + " / True");
if (!stream.BitAt (4)) {
Error ("Expecting bit 4 to be on, it was not");
Console.ReadLine();
return;
}
Console.WriteLine ("5: " + stream.BitAt (5) + " / False");
if (stream.BitAt (5)) {
Error ("Expecting bit 5 to be off, it was not");
Console.ReadLine();
return;
}
Console.WriteLine ("6: " + stream.BitAt (6) + " / False");
if (stream.BitAt (6)) {
Error ("Expecting bit 6 to be off, it was not");
Console.ReadLine();
return;
}
Console.WriteLine ("7: " + stream.BitAt (7) + " / True");
if (!stream.BitAt (7)) {
Error ("Expecting bit 7 to be on, it was not");
Console.ReadLine();
return;
}
stream.Append (stream);
debug = stream.ToString ();
Console.WriteLine (debug);
if (debug != "1110100111101001") {
Error ("Expecting 1110100111101001, got " + debug);
Console.ReadLine();
return;
}
stream.Append ("110011");
debug = stream.ToString ();
Console.WriteLine (debug);
if (debug != "1110100111101001110011") {
Error ("Expecting 1110100111101001110011, got " + debug);
Console.ReadLine();
return;
}
try {
stream.Append("1A");
Error("ERROR! Should not be able to insert A");
Console.ReadLine();
return;
}
catch (System.Exception e) {
Console.WriteLine ("Was not able to insert A (As expected)");
}
debug = stream.ToString ();
Console.WriteLine (debug);
if (debug != "11101001111010011100111") {
Error ("Expecting 11101001111010011100111, got " + debug);
Console.ReadLine();
return;
}
Console.WriteLine(stream.ByteAt (0) + " / 233");
if (stream.ByteAt (0) != 233) {
Error ("Expected byte at 0 to be 233, not: " + stream.ByteAt (0));
Console.ReadLine();
return;
}
Console.WriteLine (stream.ByteAt (1) + " / 233");
if (stream.ByteAt (1) != 233) {
Error ("Expected byte at 1 to be 233, not: " + stream.ByteAt (1));
Console.ReadLine();
return;
}
Console.WriteLine (stream.ByteAt (2) + " / 206");
if (stream.ByteAt (2) != 206) {
Error ("Expected byte at 2 to be 206, not: " + stream.ByteAt (2));
Console.ReadLine();
return;
}
Console.WriteLine ("Num bytes: " + stream.ByteCount + " / 3");
if (stream.ByteCount != 3) {
Error ("Expecting ByteCount to be 3, not: " + stream.ByteCount);
Console.ReadLine();
return;
}
Console.WriteLine ("Num bits: " + stream.BitCount + " / 23");
if (stream.BitCount != 23) {
Error ("Expecting BitCount to be 23, not: " + stream.BitCount);
Console.ReadLine();
return;
}
Console.WriteLine (stream.ToString ());
byte[] bits = stream.Bytes;
for (int i = 0; i < bits.Length; ++i) {
Console.Write(Convert.ToString(bits[i], 2).PadLeft(8, '0'));
}
Console.Write ("\n");
Console.ReadLine();
}
