get_string

# File lib/resolv.rb, line 1597
        def get_string
          raise DecodeError.new("limit exceeded") if @limit <= @index
          len = @data.getbyte(@index)
          raise DecodeError.new("limit exceeded") if @limit < @index + 1 + len
          d = @data.byteslice(@index + 1, len)
          @index += 1 + len
          return d
        end