#include <iostream.h> 
/* Returns number of characters successfully written to win.*/ 
extern int write_to_window (window* win, char* text, int length); 

class windowbuf : public streambuf { 
      window* win; 
   public: 
      windowbuf (window* w) { win = w; } 
      int sync (); 
      int overflow (int ch); 
      // Defining xsputn is an optional optimization. 
      // (streamsize was recently added to ANSI C++, not portable yet.) 
      streamsize xsputn (char* text, streamsize n); 
}; 

int windowbuf::sync () 
{ streamsize n = pptr () - pbase (); 
  return (n && write_to_window (win, pbase (), n) != n) ? EOF : 0; 
} 
int windowbuf::overflow (int ch) 
{ streamsize n = pptr () - pbase (); 
      if (n && sync ()) 
         return EOF; 
      if (ch != EOF) 
       { 
         char cbuf[1]; 
         cbuf[0] = ch; 
         if (write_to_window (win, cbuf, 1) != 1) 
            return EOF; 
       } 
      pbump (-n); // Reset pptr(). 
      return 0; 
} 
streamsize windowbuf::xsputn (char* text, streamsize n) 
{ return sync () == EOF ? 0 : write_to_window (win, text, n); } 

int 
main (int argc, char**argv) 
{ 
   window *win = ...; 
   windowbuf wbuf(win); 
   ostream wstr(&wbuf); 
   wstr << "Hello world!\n"; 
}