put_labels

# File lib/resolv.rb, line 1296
        def put_labels(d)
          d.each_index {|i|
            domain = d[i..-1]
            if idx = @names[domain]
              self.put_pack("n", 0xc000 | idx)
              return
            else
              @names[domain] = @data.length
              self.put_label(d[i])
            end
          }
          @data << "\0"
        end