code: public void unreadFrame() throws BitstreamException
  	{
  		if (wordpointer==-1 && bitindex==-1 && (framesize>0))
  		{
  			try
  			{
  				source.unread(frame_bytes, 0, framesize);
  			}
  			catch (IOException ex)
  			{
  				throw newBitstreamException(STREAM_ERROR);
  			}
  		}
  	}
docs: REVIEW: add new error codes for this.