Change executable file constants in C++.

main.cpp

#include <iostream>
#include <fstream>
#include <string>
#include <windows.h>
#include <direct.h>

const char* test[] = { "UNIQUE_START_TOKEN", "WELCOME\0------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------", "UNIQUE_END_TOKEN" };

int main(int argc, const char** argv)
{
    // Executable directory
	std::string executablePath(300, '\0');
    // Executable full path
	std::string exceutableFullPath(300, '\0');
    _getcwd((char*)executablePath.c_str(), 300);
    GetModuleFileNameA(NULL, (char*)exceutableFullPath.c_str(), 300);
	executablePath = executablePath.c_str();
    exceutableFullPath = exceutableFullPath.c_str();
    std::cout << "1. Show constant\n2. Change constant\n";
    int choise = 0;
    std::cin >> choise;
    if (choise == 2)
    {
        std::string newConstant;
        std::cout << "New Constant value:";
        std::cin.get();
        std::getline(std::cin, newConstant);
        if (newConstant.size() > 255) 
        {
            std::cout << "ERROR: Maximum allowed size for string is :" << 255 << std::endl;
        }
        std::ifstream fileRead(argv[0], std::ios::binary);
        fileRead.seekg(0, std::ios::end);
        unsigned int size = fileRead.tellg();
        std::string fileContent(size + newConstant.size(), ' ');
        fileRead.seekg(0);
        fileRead.read(&fileContent[0], size);
        fileRead.close();
        int startPos = -1;
        int endPos = -1;
        for (int i = 0; i < size; i++)
        {
            // Check for start token exists
            if (fileContent[i] == test[0][0])
            {
                for (int j = 1; j < strlen(test[0]) && i + j < size; j++)
                {
                    if (fileContent[i + j] != test[0][j])
                    {
                        break;
                    }
                    // start token matched
                    if (j == strlen(test[0]) - 1)
                    {
                        j++;
                        while (fileContent[i + j] == 0) 
                        {
                            j++;
                        }
                        startPos = i + j;
                        break;
                    }
                }
            }

            // Check for end token exists
            if (fileContent[i] == test[2][0])
            {
                for (int j = 1; j < strlen(test[2]) && i + j < size; j++)
                {
                    if (fileContent[i + j] != test[2][j])
                    {
                        break;
                    }
                    // end token matched
                    if (j == strlen(test[2]) - 1)
                    {
                        endPos = i - 1;
                        break;
                    }
                }
            }
        }

        // Did not find tokens so stop modify executable
        if (startPos == -1 || endPos == -1)
        {
            std::cout << "ERROR: TOKEN NOT FOUND!\n";
            return -1;
        }

        // Put new constant value in file content
        for (int i = 0; i < newConstant.length(); i++)
        {
            fileContent[startPos + i] = newConstant[i];
        }
        fileContent[startPos + newConstant.size()] = '\0';

        // write replaced content in temp file
        std::ofstream fileWrite("temp.exe", std::ios::binary);
        fileWrite.write(&fileContent[0], size);
        fileWrite.close();

        // rename current running file and rename temp file to original running file name
        std::string copyCommand = "del \"" + executablePath + "\\old.exe\" >nul 2>&1 & rename \"" + exceutableFullPath + "\" old.exe & rename \"" + executablePath + "\\temp.exe\" \"" + exceutableFullPath.substr(exceutableFullPath.find_last_of("/\\") + 1) + "\"";
        if (system(copyCommand.c_str()) == 0) 
        {
            std::cout << "\nREPLACED SUCCESSFULLY\n";
        }
    }
    else
    {
        std::cout << test[1] << std::endl;
    }
    return 0;
}