# File lib/aws/core/signature/version_4.rb, line 111
        def hexdigest value
          digest = Digest::SHA256.new
          if value.respond_to?(:read)
            chunk = nil
            chunk_size = 1024 * 1024 # 1 megabyte
            digest.update(chunk) while chunk = value.read(chunk_size)
            value.rewind
          else
            digest.update(value)
          end
          digest.hexdigest
        end