def update_selectables
      @readables.clear
      @writables.clear

      @items.each do |poll_item|
        #FIXME: spec for sockets *and* file descriptors
        if poll_item.readable?
          @readables << (poll_item.socket.address.zero? ? poll_item.fd : @raw_to_socket[poll_item.socket.address])
        end
        
        if poll_item.writable?
          @writables << (poll_item.socket.address.zero? ? poll_item.fd : @raw_to_socket[poll_item.socket.address])
        end
      end
    end
def update_selectables
      @readables.clear
      @writables.clear

      @items.each do |poll_item|
        #FIXME: spec for sockets *and* file descriptors
        if poll_item.readable?
          @readables << (poll_item.socket.address.zero? ? poll_item.fd : @raw_to_socket[poll_item.socket.address])
        end
        
        if poll_item.writable?
          @writables << (poll_item.socket.address.zero? ? poll_item.fd : @raw_to_socket[poll_item.socket.address])
        end
      end
    end
Update readables and writeables