anchor.diff:  
   handle_stop( Reason, State ) ->
       ok = stop_driver( State#state.port ),
  -    State#state.owner ! { stop, Reason, State#state.id }.
  +    send_owner( State, stop, Reason ).
   
   -spec stop_driver( port() ) -> ok.
   stop_driver( Port ) ->
  
positive.code: %% ===================================================================
  %% Internal functions
  %% ===================================================================
  
  -spec start_driver( string() | binary(), [ string() | binary() ] ) ->
      { ok, port() } | { error, term() }.
  
negative.code:     case start_driver( Driver, Params ) of
          { ok, Port } ->
              Info = [ erlang:port_info( Port, os_pid ) ],
              send_owner( State, start, { ok, Info } ),
              { noreply, State#state{ port = Port } };
          Error ->
              send_owner( State, start, Error ),
              { stop, Error , State }
      end;
  
  