public interface FilterBuffer { 
  // returns current contents of buffer and clears it. Returns a zero-length
  // array if its internal buffer is empty and the FilterBuffer has been closed
  char[] read ();
  // write str to buffer if str.length is less than maxBufferSize,
  // otherwise throws exception
  void write(char[] str) throws bufTooSmallException;

  int getMaxBufferSize(); 

  // informs the FilterBuffer that no more data will be written to it
  void close();

  // doesn't return until the buffer is empty
  void flush();
}