basic_stringbuf<charT,traits,Allocator>* rdbuf() const;
Returns: const_cast<basic_stringbuf<charT,traits,Allocator>*>(&sb).
basic_string<charT,traits,Allocator> str() const;
Returns: rdbuf()->str().
void str(const basic_string<charT,traits,Allocator>& s);
Effects: Calls rdbuf()->str(s).