# File lib/mongo/gridfs/grid_io.rb, line 237
    def close
      if @mode[0] == ?w
        if @current_chunk['n'].zero? && @chunk_position.zero?
          warn "Warning: Storing a file with zero length."
        end
        @upload_date = Time.now.utc
        id = @files.insert(to_mongo_object)
      end
      id
    end