31 Input/output library [input.output]

31.6 Stream buffers [stream.buffers]

31.6.3 Class template basic_streambuf [streambuf] Public member functions [streambuf.members] Put area [streambuf.pub.put]

int_type sputc(char_type c);
Effects: If the output sequence write position is not available, returns overflow(traits​::​to_int_type(c)).
Otherwise, stores c at the next pointer for the output sequence, increments the pointer, and returns traits​::​to_int_type(c).
streamsize sputn(const char_type* s, streamsize n);
Returns: xsputn(s, n).