       return @_endSync()
     else
       throw new NotImplementedError()
+  endSync: @::freeSync
 
   nextKeys: (callback) ->
     @_nexting = true

    @_indexOfKeys = -2
    @_ended = true

  endSync: ->
    if @_indexOfKeys?
      return @_endKeys()
    else if @_endSync

    else
      @_ended = true
      @_end callback
  end: @::free
