31 Input/output library [input.output]

31.9 Span-based streams [span.streams]

31.9.5 Class template basic_ospanstream [ospanstream] Constructors [ospanstream.cons]

explicit basic_ospanstream(std::span<charT> s, ios_base::openmode which = ios_base::out);
Effects: Initializes the base class with basic_ostream<charT, traits>(addressof(sb)) and sb with basic_spanbuf<charT, traits>(s, which | ios_base​::​out) ([spanbuf.cons]).
basic_ospanstream(basic_ospanstream&& rhs) noexcept;
Effects: Initializes the base class with std​::​move(rhs) and sb with std​::​move(rhs.sb).
Next, basic_ostream<charT, traits>​::​set_rdbuf(addressof(sb)) is called to install the contained basic_spanbuf.