# File lib/fog/aws/glacier.rb, line 42
        def reduce_digests(digests)
          while digests.length > 1
            digests = digests.each_slice(2).map do |pair|
              if pair.length == 2
                OpenSSL::Digest::SHA256.digest(pair[0]+pair[1])
              else
                pair.first
              end
            end
          end
          digests.first
        end