RunVoicemeeter

std::string QueryRegistry(std::string path, std::string key) {
#ifndef KEY_WOW64_32KEY
    #define KEY_WOW64_32KEY 0x0200
#endif
    constexpr DWORD NO_OPTIONS = 0;
    HKEY handle;
    long result = RegOpenKeyEx(HKEY_LOCAL_MACHINE, path.c_str(), NO_OPTIONS, KEY_READ, &handle);
    if(result != ERROR_SUCCESS) {
        result = RegOpenKeyEx(HKEY_LOCAL_MACHINE, path.c_str(), NO_OPTIONS, KEY_READ | KEY_WOW64_32KEY, &handle);
        if(result != ERROR_SUCCESS) {
            throw (unsigned long)result;
        }
    }
    DWORD required_size = 0;
    // buffer of nullptr writes the size of the data in the size parameter
    RegQueryValueEx(handle, key.c_str(), nullptr, nullptr, nullptr, &required_size);
    DWORD value_type, buffer_size = required_size;
    std::vector<char> buffer(buffer_size);
    result = RegQueryValueEx(handle, key.c_str(), nullptr, &value_type, (BYTE*)buffer.data(), &buffer_size);
    if(result != ERROR_SUCCESS) {
        throw (unsigned long)result;
    }
    return std::string(buffer.data(), buffer_size);
}

std::string parent_path(std::string path) {
    const char delimiter = '\\';
    using it = std::string::iterator;
    it begin = path.begin(), end = path.begin();
    it current = path.begin();
    while(current != path.end()) {
        if(*current == delimiter)
            end = current;
        ++current;
    }
    return {begin, end};
}

std::string VoicemeeterInstallPath() {
    const std::string key = R"(SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Uninstall\\VB:Voicemeeter {17359A74-1236-5467})";
    std::string path = QueryRegistry(key, "UninstallString");
    return parent_path(path);
}

void RunExe(std::string exe, std::string working_dir) {
    ShellExecuteA(nullptr, "open", exe.c_str(), working_dir.c_str(), working_dir.c_str(), SW_SHOW);
}

void RunVoicemeeter() {
    std::string install_path = VoicemeeterInstallPath();
    std::string exe = install_path + "\\voicemeeterpro.exe";
    RunExe(exe, install_path);
}