[streambuf.assign]
31 Input/output library [input.output]
31.6 Stream buffers [stream.buffers]
31.6.3 Class template basic_streambuf [streambuf]
31.6.3.4 Protected member functions [streambuf.protected]
31.6.3.4.1 Assignment [streambuf.assign]
basic_streambuf& operator=(const basic_streambuf& rhs);
void swap(basic_streambuf& rhs);