# File lib/backports/random/bits_and_bytes.rb, line 15
      def random_integer(upto)
        n = upto - 1
        nb_full_32 = 0
        while n > PAD_32_BITS
          n >>= 32
          nb_full_32 += 1
        end
        mask = mask_32_bits(n)
        begin
          rand = random_32_bits & mask
          nb_full_32.times do
            rand <<= 32
            rand |= random_32_bits
          end
        end until rand < upto
        rand
      end