unknown C++ heap-corruption in InDev bit based encryption program, new to C++ programming

Ok, I've been trying to self learn C++ and as such decided to try make an encrypt/decrypt program. The idea is to open a file and edit bits according to the password. I'm having some problems with my code and by using break-points I have found that the error arises when I open the file (it is in the main() about a third of the way down). Visual C++ tells me that the heap has become corrupt, and I'm at a loss as to why. Any help would be greatly appreciated.

#include <iostream>
#include <fstream>
#include <sstream>
#include <stdio.h>
#include <fstream>
#include <sys/stat.h>
using namespace std;
unsigned char fileData[31];
bool *password;
int count(0), maxCount;

/*
* Programmer:       P7r0
* Program:          Encrypt/Decrypt
* Version:          InDev
* Date Released:    -
*
* Notes:
*   -
*/

struct bits{
    // Breaks each byte into its 8 bits
    unsigned int b1 : 1;
    unsigned int b2 : 1;
    unsigned int b3 : 1;
    unsigned int b4 : 1;
    unsigned int b5 : 1;
    unsigned int b6 : 1;
    unsigned int b7 : 1;
    unsigned int b8 : 1;
} ;

// Toggles the bits, ie if 1 make 0
int swap(int Obj){
    if (Obj = 1){return 0;}
    else if (Obj = 0){return 1;}
}

void conversion(string convert){
    // User password to a boolean array
    int ascii, loop, count, a, counter(0);
    const char *code;
    bool bin [ ] = {false,false,false,false,false,false,false,false};
    // Create an array for the booleans
    password = new bool [convert.length()];
    code = convert.c_str();
    for (loop = 0;loop < convert.length(); loop++){
        for (a = 0;a < 8;a++){bin[a] = false;}
        // Get the equivilent ASCII code
        ascii = int(code[loop]);
        while (ascii > 0){
            // Develop a tempory binary array with code based off of the ASCII values
            if (ascii >= 128){ascii -= 128;bin[0] = true;}
            else if (ascii >= 64){ascii -= 64;bin[1] = true;}
            else if (ascii >= 32){ascii -= 32;bin[2] = true;}
            else if (ascii >= 16){ascii -=开发者_如何学Python 16;bin[3] = true;}
            else if (ascii >= 8){ascii -= 8;bin[4] = true;}
            else if (ascii >= 4){ascii -= 4;bin[5] = true;}
            else if (ascii >= 2){ascii -= 2;bin[6] = true;}
            else if (ascii >= 1){ascii -= 1;bin[7] = true;}
        }
        for (count = 0; count < 8; count++){
            // Move out of the tempory array into the main array for global use
            //cout << bin[count];
            password[counter] = bin[count];
            counter++;
        }
        //cout << ":\n";
    }
}

int encrypt(int loop){
    // Changes everything bit by bit in blocks of bytes the size of loop, typically 32
    int a, b, counter(0);
    bits bit;
    for (a = 0; a == loop; a++){
        bit = * (bits*)(&fileData[a]);
        cout << bit.b1 << "\t";
        for (b = 0; b == 7; b++){
            if (count = maxCount){count = 0;}
            if (password[count] = true){
                // If current password array is true then toggle current bit
                if (b = 0){bit.b1 = swap(bit.b1);}
                else if (b = 1){bit.b2 = swap(bit.b2);}
                else if (b = 2){bit.b3 = swap(bit.b3);}
                else if (b = 3){bit.b4 = swap(bit.b4);}
                else if (b = 4){bit.b5 = swap(bit.b5);}
                else if (b = 5){bit.b6 = swap(bit.b6);}
                else if (b = 6){bit.b7 = swap(bit.b7);}
                else if (b = 7){bit.b8 = swap(bit.b8);}
                count++;}
            else {count++;}
        }
        cout << counter;
        fileData[counter] = *(unsigned char*)(&bit);
        counter++;
    }
    return 0;
}

int main(){
    fstream file;
    char *remainder;
    int counter, size, temp, b(0), stackCount(0);
    long begin, end;
    string usrin, pass, pause, filedir;
    cout << "Please input password, must be one word\n";
    cin >> pass;
    maxCount = pass.length();
    conversion(pass);
    // Change password data stored at its location as to avoid unwanted detection of the password
    pass = "default";
    cout << "\nPlease input file path\n";
    cin >> filedir;
    //The error seems to be here
    file.open(filedir.c_str(),ios::in | ios::out | ios::binary);
    // Check that the file is open
    if (file.is_open()){
        cout << "Encrypting...\n";
        counter = 32;
        // Work out size (bytes) of the file
        begin = file.tellg();
        file.seekg(0,ios::end);
        end = file.tellg();
        file.seekg(0,ios::beg);
        b = file.tellg();
        size = end-begin;
        while((int)b <= size){
            // Had to typecast as the unsigned/signed mis-match was throwing compile errors
            file.read((char*)(&fileData),counter);
            encrypt(counter);
            if (size - b >= 32){
                file.write((char*)(&fileData),counter);
                b = file.tellg();
            } else if (size - b < 32 && size - b > 0) {
                remainder = new char [size - b];
                for (int a = 0; a != size - b; a++){remainder[a] = fileData[a];}
                file.write((char*)(remainder),size - b);
                // To cancel out of the while loop
                b += 1;
            } else if (size - b == 0){b += 1;}
        }
        file.close();
        cout << "\nEncrypted.\nPlease enter a letter to continue\n";
        cin >>  pause;
    // Prompt user if unable to open the file
    } else {cout << "Failed to open the file";}
    return 0;
}

In your conversion()-method you have the following code:

int counter(0);
// ...
password = new bool [convert.length()];
// ...
for (count = 0; count < 8; count++){
    password[counter] = bin[count];
    counter++;
}

If the length of convert is less than 8, you will be writing outside the password-array inside the loop.

A heap-corruption will usually not be detected at once, which is why you do not get the error until opening the file.

Not sure if this is the cause of your problem, but in any case it is unwise to write directly to the file that you are reading from. Write to a temp file and rename the files when done.