31 Input/output library [input.output]

31.6 Stream buffers [stream.buffers]

31.6.3 Class template basic_streambuf [streambuf]

31.6.3.3 Public member functions [streambuf.members]

31.6.3.3.4 Putback [streambuf.pub.pback]

int_type sputbackc(char_type c);

Effects: If the input sequence putback position is not available, or iftraits::eq(c, gptr()[-1]) is false, returnspbackfail(traits::to_int_type(c)).

Otherwise, decrements the next pointer for the input sequence and returnstraits::to_int_type(*gptr()).

int_type sungetc();

Effects: If the input sequence putback position is not available, returnspbackfail().