# File lib/fog/aws/storage.rb, line 155
        def signed_url(params, expires)
          refresh_credentials_if_expired

          #convert expires from a point in time to a delta to now
          expires = expires.to_i
          if @signature_version == 4
            params = v4_signed_params_for_url(params, expires)
          else
            params = v2_signed_params_for_url(params, expires)
          end

          params_to_url(params)
        end