gistfile1.txt

namespace url {

class basic_value
{
    char* s_;

public:
    // construct a URL from a string.
    // the string is copied.
    basic_value( string_view s );

    // return the hostname
    string_view
    encoded_hostname() const noexcept;

protected:
    virtual
    char*
    reserve(
        char* buffer,
        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 = basic_value<std::allocator<char>>;

}