1) Gets aspan referencing the written area ifstd::ios_base::out is set in the open mode, or aspan referencing the underlying buffer otherwise.

2) Makes thebasic_spanbuf perform I/O on the buffer referenced bys. Sets pointers to get area, put area, or both.

Set bits in open mode (affecting pointers to get area)	Return value after setting
	eback()	gptr()	egptr()
std::ios_base::in	s.data()	s.data()	s.data()+ s.size()
Set bits in open mode (affecting pointers to put area)	Return value after setting
	pbase()	pptr()	epptr()
std::ios_base::out&&!std::ios_base::ate	s.data()	s.data()	s.data()+ s.size()
std::ios_base::out&&std::ios_base::ate	s.data()	s.data()+ s.size()	s.data()+ s.size()

1)std::span<CharT>(pbase(), pptr()) ifstd::ios_base::out is set in the open mode, or astd::span<CharT> that references the whole underlying buffer otherwise.

2) (none)