30 Input/output library [input.output]

30.6 Stream buffers [stream.buffers]

30.6.3 Class template basic_­streambuf [streambuf]

30.6.3.2 basic_­streambuf public member functions [streambuf.members]

30.6.3.2.4 Putback [streambuf.pub.pback]

int_type sputbackc(char_type c);

Returns: If the input sequence putback position is not available, or if traits​::​eq(c, gptr()[-1]) is false, returns pbackfail(traits​::​to_­int_­type(c)). Otherwise, decrements the next pointer for the input sequence and returns traits​::​to_­int_­type(*gptr()).

int_type sungetc();

Returns: If the input sequence putback position is not available, returns pbackfail(). Otherwise, decrements the next pointer for the input sequence and returns traits​::​to_­int_­type(*gptr()).