Reading encrypted text in program in c++ - visual-studio-2010

Question

I need some help to decrypt my text file and make it able to read in my program..
What I have programmed so far is to read the encrypted file, create a new file, decrypt it and read the newly created file..
I need to decrypt the encrypted file without having to create a new file that reads the decrypted text..
Well, Let me show you my code:
P.S Most of the include is not needed and I already know that
Visual studio 2010 Windows Form Application CLR
#pragma once
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <conio.h>
#include <stdio.h>
#include <iomanip>
namespace EncryptandDecryptfiletest {
using namespace System;
using namespace System::ComponentModel;
using namespace System::Collections;
using namespace System::Windows::Forms;
using namespace System::Data;
using namespace System::Drawing;
using namespace System::IO;
using namespace std;
private: System::Void Form1_Load(System::Object^ sender, System::EventArgs^ e) {
/*Decryption --- When program loads*/
char ch,mod;
char key = 97;
char name[100] = "Encrypted.txt";
char target[100] = "TTO.txt";
ifstream fin("Encrypted.txt", ios::binary); // Reading file
if(!fin) //open the encrypted file in a binary mode
{
MessageBox::Show("Encrypted.txt did not open"); //If file does not exist
} //or any kind of error
ofstream fout;
fout.open(target,ios::binary); //Opens outputfile
if(!fout)
{ //Show error if any error occurs in opening new file
MessageBox::Show("TTO.txt did not open");
}
while(fin.get(ch))
{ // opens the Encrypted file
if(ch==EOF)break;
mod = ch + key;
if (mod > 255 ) mod -= 255;
fout << mod; //Writes decrypted text to TTO.txt
}
fin.close(); //Close the encrypted file
fout.close(); // Close the decrypted file
}
private: System::Void comboBox1_SelectedIndexChanged(System::Object^ sender, System::EventArgs^ e) {
label1->Text = comboBox1->Text;
pictureBox1->Load("Images\\" + comboBox1->SelectedItem->ToString() + ".png");
//String^ openFileTest = "Encrypted.txt"; // Opens the encrypted .txt file
String^ openFileTest = "TTO.txt"; //Opens the newly created file that is decrypted
try //Reading the .txt file
{
StreamReader^ DataIn = File::OpenText(openFileTest);
String^ DataStr;
int count = 0;
array<String^>^ result;
array<Char>^ separ = gcnew array<Char>{'"'}; //After each Quote gets a new value of result[x]
while((DataStr = DataIn->ReadLine()) != nullptr)
{
count++;
result = DataStr->Split(separ);
if(comboBox1->Text == result[0]) // result[0] = Name
{
textBox1->Text = result[1]; //reads first word in txt file
textBox2->Text = result[2]; //second word in txt file
textBox3->Text = result[3]; //third word in txt file
}
} // ends while()
} // ends try
catch (Exception^ e)
{
if(dynamic_cast<FileNotFoundException^>(e))
MessageBox::Show("File " + openFileTest + " not found");
}
} // Ends comboBox1_SelectedIndexChanged void
};
}
You have my decryption code and the code I want to use..
I have uploaded the code for you to use on your computer because it is fairly hard for me to explain..
I want to be able to read the encrypted file in my program, without having to writing a new file to decrypt it..
I hope anyone is able to help me
Decrypted & Encrypted .txt file Included (And images)
--> Program .rar pack link <--
Build it with Visual Studio 2010

Answer 1

Just replace the output file stream with a MemoryStream.
The first thing to do is decompose into functions. Since you read your streams byte per byte, you won't need readers, which is good.
void Decrypt(Stream^ input, Stream^ output)
{
char key=97;
int byteRead;
while((byteRead=input->ReadByte()) >= 0)
{
char ch = (char)byteRead;
char mod = (char)(ch+key)
output->WriteByte(mod);
}
}
//When loading
MemoryStream^ ms = gcnew MemoryStream();
{
FileStream^ fs = File::OpenRead(L"encrypted.txt");
Decrypt(fr, ms);
delete fs;
}
ms.Seek(0, SeekOrigin::Begin);
//Later, read from the memory stream