bool isKey = true;
        std::string lastKey;
        std::string lastValue;
        for (size_t i = 0, size = url.size (); i < size; ++i)
        {
            std::string& current = isKey ? lastKey : lastValue;

            const char ch = url [i];

            if (ch == '%')
            {
                if (i + 3 > size)
                {
                    IsValid_ = false;
                    return;
                }
                int val = 0;
                std::istringstream is (url.substr (i + 1, 2));
                if (is >> std::hex >> val)
                {
                    current += static_cast<char> (val);
                    i += 2;
                }
                else
                {
                    IsValid_ = false;
                    return;
                }
            }
            else if (ch == '+')
                current += ' ';
            else if (ch == '=')
            {
                if (isKey)
                    isKey = false;
                else
                {
                    IsValid_ = false;
                    return;
                }
            }
            else if (ch == '&')
            {
                isKey = true;
                Params_ [lastKey] = lastValue;
                lastKey.clear ();
                lastValue.clear ();
            }
            else
                current += ch;
        }
        if (lastKey.size ())
            Params_ [lastKey] = lastValue;