gistfile1.txt

namespace url {

class basic_value
{
public:
    basic_value() = default;

    // return the hostname
    string_view
    encoded_hostname() const noexcept
    {
        if(size() == 0)
            return {};
        return {
            data(), size() };
    }

    // set the hostname
    basic_value&
    set_hostname( string_view s )
    {
        resize( 0 );
        resize( s.size() );
        std::copy( s.begin(), s.end(), data() );
        return *this;
    }

protected:
    virtual char* data() noexcept = 0;
    virtual char const* data() const noexcept = 0;
    virtual std::size_t size() const noexcept = 0;
    virtual void resize(std::size_t n) = 0;
};

template<class Allocator>
class dynamic_value : public basic_value
{
    Allocator a_;
    ...
};

template<std::size_t N>
class static_value : public basic_value
{
    char buf_[N+1]; // for the null
};

using value = dynamic_value<std::allocator<char>>;