code: final void handleProcessedBuffer(T buffer, IOException ex) {
  		
  		if (ex != null && this.exception == null) {
  			this.exception = ex;
  		}
  		
  		returnBuffer(buffer);
  	}
docs: Handles a processed <tt>Buffer</tt>. This method is invoked by the
  asynchronous IO worker threads upon completion of the IO request with the
  provided buffer and/or an exception that occurred while processing the request
  for that buffer.
  
  @param buffer The buffer to be processed.
  @param ex The exception that occurred in the I/O threads when processing the buffer's request.