result out(stateT& state,
const internT* from, const internT* from_end, const internT*& from_next,
externT* to, externT* to_end, externT*& to_next) const;
Returns: do_out(state, from, from_end, from_next, to, to_end, to_next)
result unshift(stateT& state,
externT* to, externT* to_end, externT*& to_next) const;
Returns: do_unshift(state, to, to_end, to_next)
result in(stateT& state,
const externT* from, const externT* from_end, const externT*& from_next,
internT* to, internT* to_end, internT*& to_next) const;
Returns: do_in(state, from, from_end, from_next, to, to_end, to_next)
int encoding() const noexcept;
Returns: do_encoding()
bool always_noconv() const noexcept;
Returns: do_always_noconv()
int length(stateT& state, const externT* from, const externT* from_end,
size_t max) const;
Returns: do_length(state, from,from_end,max)
int max_length() const noexcept;
Returns: do_max_length()