def extract(event)
      event_mask = poller.event_mask_for_socket(event.socket)
      @event_masks[event.socket] = event_mask
      if event.readable?
        @readables << event.socket
        event_mask &= 0xFFFF ^ CZTop::Poller::ZMQ::POLLIN
      end
      if event.writable?
        @writables << event.socket
        event_mask &= 0xFFFF ^ CZTop::Poller::ZMQ::POLLOUT
      end
      poller.modify(event.socket, event_mask)
    end
def extract(event)
      event_mask = poller.event_mask_for_socket(event.socket)
      @event_masks[event.socket] = event_mask
      if event.readable?
        @readables << event.socket
        event_mask &= 0xFFFF ^ CZTop::Poller::ZMQ::POLLIN
      end
      if event.writable?
        @writables << event.socket
        event_mask &= 0xFFFF ^ CZTop::Poller::ZMQ::POLLOUT
      end
      poller.modify(event.socket, event_mask)
    end
Extracts the event information, adds the socket to the correct list(s)
 and modifies the socket's event mask for the socket to not turn up
 again during the next call(s) to {CZTop::Poller#wait} within {#wait}.

 @param event [CZTop::Poller::Event]
 @return [void]