[ispanstream.members]

basic_spanbuf<charT, traits>* rdbuf() const noexcept;

Effects: Equivalent to: return const_cast<basic_spanbuf<charT, traits>*>(addressof(sb));

std::span<const charT> span() const noexcept;

Effects: Equivalent to: return rdbuf()->span();

void span(std::span<charT> s) noexcept;

Effects: Equivalent to rdbuf()->span(s).

template<class ROS> void span(ROS&& s) noexcept;

Constraints: ROS models ranges::borrowed_range.

(!convertible_to<ROS, std::span<charT>>) && convertible_to<ROS, std::span<const charT>> is true.

Effects: Let sp be std::span<const charT>(std::forward<ROS>(s)).

Equivalent to: this->span(std::span<charT>(const_cast<charT*>(sp.data(), sp.size();

31 Input/output library [input.output]