29 Input/output library [input.output]

29.9 Span-based streams [span.streams]

29.9.3 Class template spanbuf [spanbuf]

29.9.3.1 General [spanbuf.general]

namespace std { template<class charT, class traits = char_traits<charT>> class basic_spanbuf : public basic_streambuf<charT, traits> { public: using char_type = charT; using int_type = typename traits::int_type; using pos_type = typename traits::pos_type; using off_type = typename traits::off_type; using traits_type = traits; // [spanbuf.ctor], constructors basic_spanbuf() : basic_spanbuf(ios_base::in | ios_base::out) {} explicit basic_spanbuf(ios_base::openmode which) : basic_spanbuf(std::span<charT>(), which) {} explicit basic_spanbuf(std::span<charT> s, ios_base::openmode which = ios_base::in | ios_base::out); basic_spanbuf(const basic_spanbuf&) = delete; basic_spanbuf(basic_spanbuf&& rhs); // [spanbuf.assign], assignment and swap basic_spanbuf& operator=(const basic_spanbuf&) = delete; basic_spanbuf& operator=(basic_spanbuf&& rhs); void swap(basic_spanbuf& rhs); // [spanbuf.members], member functions std::span<charT> span() const noexcept; void span(std::span<charT> s) noexcept; protected: // [spanbuf.virtuals], overridden virtual functions basic_streambuf<charT, traits>* setbuf(charT*, streamsize) override; 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; private: ios_base::openmode mode; // exposition only std::span<charT> buf; // exposition only }; template<class charT, class traits> void swap(basic_spanbuf<charT, traits>& x, basic_spanbuf<charT, traits>& y); }
The class template basic_­spanbuf is derived from basic_­streambuf to associate possibly the input sequence and possibly the output sequence with a sequence of arbitrary characters.
The sequence is provided by an object of class span<charT>.
For the sake of exposition, the maintained data is presented here as:
  • ios_­base​::​openmode mode, has in set if the input sequence can be read, and out set if the output sequence can be written.
  • std​::​span<charT> buf is the view to the underlying character sequence.