Programming Challenge 12.9 - File Encryption Filter

Example Files: long.txt
                          encrypted.txt


/* File Encryption Filter - File encryption is the science of writing the
    contents of a file in secret code. This encryption program works like
    a filter, reading the contents of one file, modifying the data into a
    code, and then writing the coded contents out to a second file. The
    second file is a version of the first file, but written in secret code. */

#include "Utility.h"

int  readFile(fstream &, string &);
string encryptText(string);
int writeFile(fstream &, const string);

int main()
{
    fstream textFile;
    fstream textCrypt;

    int    fOpen = 0;
    string clearText = "";
    string encrypted = "";

    cout << "File Encryption Filter\n\n";

    fOpen = readFile(textFile, clearText);

    if (fOpen != -1)
    {
        cout << "\nYour file will be encrypted now ...\n";
        encrypted = encryptText(clearText);

        cout << "File encrypted. Writing encrypted text to file ...\n";
        writeFile(textCrypt, encrypted);

        if (fOpen != -1)
        {
            cout << "\nFile successfully created. You can now close this program.\n"
                  << "Have a nice day!";
        }
    }

   pauseSystem();
   return 0;
}

/* **********************************************************
    Definition: readFile

    This function uses a reference parameter to an fstream
    object and a reference to a string object as parameters.
    Upon success, the contents of the file is read-in and
    stored in a string object.
   ********************************************************** */

int readFile(fstream &textFile, string &clearText)
{
    string fileName = "";
    string tmpText = " ";

    cout << "Enter name of file you wish to open: ";
    cin >> fileName;

    textFile.open(fileName, ios::in);

    if (!textFile.fail())
    {
        while (getline(textFile, tmpText))
        {
            clearText += tmpText + " ";
        }
    }
    else
    {
        cout << "\nFile Read Error. Could not read " << fileName;
        return -1;
    }
    textFile.close();

    return 0;
}

/* **********************************************************
    Definition: encryptText

    This function uses a string object as parameters. The
    contents in the string object is encrypted, and the string
    returned.
   ********************************************************** */

string encryptText(string encrypted)
{
    int basEnc = 0;
    int locEnc = 0;
    int locFin = 0;
    int locTxt = 0;

    basEnc = 32 / 3;
    locEnc = (5 + (basEnc + 5) * (basEnc + basEnc / 8));
    locFin = ((3 * basEnc) + (locEnc - 6));
    locTxt = ((1 - (basEnc + locEnc) * (basEnc + locEnc)) + locFin);

    for (int i = 0; i < encrypted.size(); i++)
    {
        encrypted[i] += locTxt + locFin / locEnc;       
    }

    return encrypted;
}

/* **********************************************************
    Definition: writeFile

    This uses a reference to an fstream object and a constant
    string object variable as parameters. Upon success, the
    file is opened, and the encrypted text contained in the
    string object is written to it.
   ********************************************************** */

int writeFile(fstream &cryptText, const string encrypted)
{
    string fileName = "";

    cout << "\nEnter name of file you wish to write to: ";
    cin >> fileName;

    cryptText.open(fileName, ios::out);
   
    if (!cryptText.fail())
    {   
        cryptText << encrypted;
    }
    else
    {
        cout << "File Write Error. Could not write data to " << fileName;
        return -1;
    }
    cryptText.close();

    return 0;
}

Example Output: