explicit basic_spanbuf(std::span<charT> s,
ios_base::openmode which = ios_base::in | ios_base::out);
basic_spanbuf(basic_spanbuf&& rhs);
basic_spanbuf& operator=(basic_spanbuf&& rhs);
void swap(basic_spanbuf& rhs);
template<class charT, class traits>
void swap(basic_spanbuf<charT, traits>& x, basic_spanbuf<charT, traits>& y);
std::span<charT> span() const noexcept;
void span(std::span<charT> s) noexcept;
pos_type seekoff(off_type off, ios_base::seekdir way,
ios_base::openmode which = ios_base::in | ios_base::out) override;
pos_type seekpos(pos_type sp, ios_base::openmode which = ios_base::in | ios_base::out) override;
basic_streambuf<charT, traits>* setbuf(charT* s, streamsize n) override;