Filename: main.cpp

#include "HuffmanTree.h"

#include <string>

#include <fstream>

using namespace std;

//function prototypes

void GenerateFrequenciesFromFile(ifstream & , vector<HuffmanTreeNodePtr> &);

bool OpenFileForReading (string , ifstream & );

bool OpenFileForWriting (string , ofstream & );

void main()

{

//generate code from text file

ifstream text;

if(! OpenFileForReading("text.txt", text)) return;

ofstream codetable;

if(! OpenFileForWriting("codetable.txt", codetable)) return;

vector<HuffmanTreeNodePtr> HuffmanTreeNodes;

GenerateFrequenciesFromFile(text, HuffmanTreeNodes);

HuffmanTree t(HuffmanTreeNodes);

t.PrintCode(codetable);

//use code generated to decode text file

ifstream codedtext;

if(! OpenFileForReading("codedtext.txt", codedtext)) return;

ofstream decodedtext;

if(! OpenFileForWriting("decodedtext.txt", decodedtext)) return;

t.DecodeAndPrint(codedtext,decodedtext);

}

/*

Purpose: opens a file for input

Precondition: a string containing the file name to open is passed, and an input file stream is passed

Postcondtion: true is returned if the file was open, false if an error occured

*/

bool OpenFileForReading (string fileName, ifstream & inputFileStream)

{

inputFileStream.open(&fileName[0], ios::in);

if (!inputFileStream.is_open())

{

cout << "ERROR: CAN'T OPEN FILE " << fileName << endl;

return false;

}

return true;

}

/*

Purpose: opens a file for output

Precondition: a string containing the file name to open is passed, and an output file stream is passed

Postcondtion: true is returned if the file was open, false if an error occured

*/

bool OpenFileForWriting (string fileName, ofstream & outputFileStream)

{

outputFileStream.open (&fileName[0], ofstream::out | ofstream::trunc);

//Truncate file to zero when opening, so that file is empty before you output to it

if(!outputFileStream.is_open())

{

cout << "ERROR: CAN'T OPEN FILE" << fileName << endl;

return false;

}

return true;

}

/*

Purpose: generates a vector of frequencies of the characters contained in the file

Precondition: the input file stream from which to generate is passed and an empty vector of Huffman TreeNodes is passed

Postcondtion: none

*/

void GenerateFrequenciesFromFile(ifstream & inputFileStream, vector<HuffmanTreeNodePtr> & HuffmanTreeNodes)

{

char c;

while(inputFileStream.get(c))

{

int positionOfCharacterInVector = GetPositionOfCharInVector(HuffmanTreeNodes, c);

//if character is already in vector find the character and add to its frequency

if(positionOfCharacterInVector != -1)

HuffmanTreeNodes[positionOfCharacterInVector]->IncrementFrequency();

//otherwise add the new character to the vector

else

InsertAtFrontInVector(HuffmanTreeNodes, new HuffmanTreeNode(c,1,NULL,NULL));

}

}