protected virtual member function
streambuf* setbuf (char* s, streamsize n);
Virtual function called by the public member function pubsetbuf to influence the object in a way that is dependent on the library implementation.
If both arguments are zero, the call is guaranteed to have no effect on the stringbuf object.
- s, n
If both are zero, no effect.
streamsize is a signed integral type.
If both arguments are zero, it introduces no data races.
Basic guarantee: if an exception is thrown, the object is in a valid state.