XOR Encryption

#include "Includes.h"

void XOR_Crypt(string& toCrypt, const string& key);     //simple xor (en/de)cryption
void XOR_Encrypt(string& toEncrypt, const string& key);     //more advanced xor encryption
void XOR_Decrypt(string& toDecrypt, const string& key);
string randKey(const size_t len);           //generates a random key
inline int getVal(const char& letter);      //gets the int value of the letter; a = 0, b = 1, c = 2, etc...
inline char getChar(int val);               //gets the character of a number; 0 = a, 1 = b, 2 = c, etc...

void help();
void toClipboard(const std::string &s);

void encryptFile(const string fileToEnc);
void decryptFile(const string fileToDec);
void saveToFile(const string fileName, const stringstream& data);

const char g_alpha[] = { 'a', 'b', 'c', 'd','e','f','g', 'h', 'i', 'j', 'k', 'l', 'm',
                            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
                            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
                            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
                            '1', '2', '3', '4', '5', '6', '7', '8', '9', '0' };
const size_t g_arrSize = sizeof(g_alpha) / sizeof(g_alpha[0]);
string g_encStr = "";
size_t g_txtSize = 0;

int main(int argc, char* argv[])
{
    if (argv[1] == 0)
    {
        cout << "Please open this program in a command prompt. Shift + Right Click -> Open command window here.\n"
            << "Press enter to exit...\n";
        getchar();
        exit(0);
    }
    if (argc == 1)
    {
        cout << "Usage: " << argv[0] << " -command\n" <<
            "Available commands can be shown with -help\n";
    }

    if (argv[1] == (string)"-encrypt")
    {
        // entered a file, whose content will be encrypted
        if (argc == 3)
        {
            ifstream tryOpen((string)argv[2]);
            if (tryOpen.fail())
            {
                cout << "\nFailed to open file!\n";
                exit(-1);
            }
            else
            {   // successfully opened file
                encryptFile((string)argv[2]);
            }
        }

        encryptStr();
    }
    if (argv[1] == (string)"-decrypt")
    {
        // entered a file, whose content will be decrypted
        if (argc == 3)
        {
            ifstream tryOpen((string)argv[2]);
            if (tryOpen.fail())
            {
                cout << "\nFailed to open file!\n";
                exit(-1);
            }
            else
            {   // successfully opened file
                decryptFile((string)argv[2]);
            }
        }

        decryptStr();
    }
    if (argv[1] == (string)"-help")
        help();
}

void encryptFile(const string fileToEnc)
{
    ifstream inFile(fileToEnc);
    string data = "", key = "", fileName = "";
    stringstream buffer;

    if (inFile.is_open())
    {
        cout << "~ " << fileToEnc << " opened!~\n";
        buffer << inFile.rdbuf();
        data = buffer.str();
    }
    inFile.close();

    g_txtSize = data.length();

    key = randKey(g_txtSize);
    cout << "\n~~Your key is:~~\n" << key << endl;
    toClipboard(key);
    cout << "\n~Key copied to clipboard!~\n\n";

    cout << "~Encrypting...~\n";
    //XOR_Encrypt(data, key);
    XOR_Crypt(data, key);

    buffer.str(string());       // clears stringstream contents; can also do buffer.str(""), but buffer.str(string()) is technically more efficient
    buffer << data;

    cout << "What would you want your encrypted file to be called?\n";
    cin >> fileName;

    saveToFile(fileName, buffer);

    exit(0);
}
void decryptFile(const string fileToDec)
{
    stringstream buffer;
    string data = "", key = "", fileName;

    ifstream inFile(fileToDec);
    if (inFile.is_open())
    {
        cout << "~ " << fileToDec << " opened!~\n";
        buffer << inFile.rdbuf();
        data = buffer.str();
    }
    inFile.close();

    cout << "\nEnter the key to decrypt " << fileToDec << " :\n";
    cin >> key;

    cout << "\n~Decrypting...~\n";
    //XOR_Decrypt(data, key);
    XOR_Crypt(data, key);

    buffer.str(string());
    buffer << data;

    cout << "What would you want your decrypted file to be called?\n";
    cin >> fileName;

    saveToFile(fileName, buffer);

    exit(0);
}

void saveToFile(const string fileName, const stringstream& data)
{
    ofstream outFile(fileName);
    if (outFile.is_open())
    {
        cout << "~Saving to " << fileName << " ...~\n";
        outFile << data.rdbuf();
        cout << "~Done!~\n";
    }
    outFile.close();
}

void XOR_Crypt(string& toCrypt, const string& key)
{
    for (size_t i = 0; i < toCrypt.length(); i++)
        toCrypt[i] ^= key[i];
}

string randKey(const size_t len)
{
    srand(time(NULL));

    string key = "";
    for (size_t i = 0; i < len; i++)
        key += g_alpha[rand() % g_arrSize];

    return key;
}

inline int getVal(const char& letter)
{
    for (int i = 0; i < g_arrSize; i++)
    {
        if (letter == g_alpha[i])
            return i;
    }

    return 0;
}
inline char getChar(int val)
{
    if (val < 0)
        val += g_arrSize;
    return val > g_arrSize ? g_alpha[val % g_arrSize] : g_alpha[val];
}

void toClipboard(const std::string &s) {    //courtesy of helios
    OpenClipboard(0);
    EmptyClipboard();
    HGLOBAL hg = GlobalAlloc(GMEM_MOVEABLE, s.size());
    if (!hg) {
        CloseClipboard();
        return;
    }
    memcpy(GlobalLock(hg), s.c_str(), s.size());
    GlobalUnlock(hg);
    SetClipboardData(CF_TEXT, hg);
    CloseClipboard();
    GlobalFree(hg);
}