write_snake_case.cpp

    void write_snake_case(writer& w, std::string_view const& name, bool uppercase)
    {
        auto case_func = [uppercase](char c)
        {
            return uppercase
                ? static_cast<char>(::toupper(c))
                : static_cast<char>(::tolower(c));
        };

        w.write(case_func(name[0]));
        for (std::string_view::size_type i = 1; i < name.size() - 1; i++)
        {
            if (name.substr(i, 4) == "UInt")
            {
                w.write('_');
            }

            if (isupper(name[i]) && islower(name[i + 1]))
            {
                if (name.substr(i-1, 4) != "UInt")
                {
                    w.write('_');
                }
            }

            w.write(case_func(name[i]));
        }
        w.write(case_func(name[name.size() - 1]));
    }