basic_filebuf<charT, traits>* rdbuf() const;
Returns: const_cast<basic_filebuf<charT, traits>*>(&sb).
Returns: rdbuf()->is_open().
void open(const char* s, ios_base::openmode mode = ios_base::out);
Effects: Calls rdbuf()->open(s, mode | ios_base::out). If that function does not return a null pointer calls clear(), otherwise calls setstate(failbit) (which may throw ios_base::failure) ([iostate.flags]).
Effects: Calls rdbuf()->close() and, if that function fails (returns a null pointer), calls setstate(failbit) (which may throw ios_base::failure) ([iostate.flags]).
void open(const string& s, ios_base::openmode mode = ios_base::out);
Effects: Calls open(s.c_str(), mode).