basic_streambuf* setbuf(char_type* s, streamsize n);
pos_type seekoff(off_type off, ios_base::seekdir way,
ios_base::openmode which
= ios_base::in | ios_base::out);
pos_type seekpos(pos_type sp,
ios_base::openmode which
= ios_base::in | ios_base::out);
int sync();
streamsize xsgetn(char_type* s, streamsize n);
int_type underflow();
int_type uflow();
int_type pbackfail(int_type c = traits::eof());
streamsize xsputn(const char_type* s, streamsize n);
int_type overflow(int_type c = traits::eof());