protected:
	virtual int sync();
	virtual int showmanyc() const;
	virtual streamsize xsgetn(char_type* s, streamsize n);
	virtual int_type underflow();
	virtual int_type uflow();
	virtual int_type pbackfail(int_type c = eof);
	virtual streamsize xsputn(const char_type* s, 
streamsize n);
	virtual streamsize xsgetn(char_type* s, streamsize n);
	virtual int_type overflow(int_type c = eof);

public:

	 int pubsync();
	 virtual bool is_open() const;
	 int read(void* buf, int len);
	 int write(const void* buf, int len);
	 long howmanyc() const;