    # File lib/rack/content_length.rb, line 14
        def call(env)
          status, headers, body = @app.call(env)
          headers = HeaderHash.new(headers)

          if !STATUS_WITH_NO_ENTITY_BODY.include?(status.to_i) &&
             !headers[CONTENT_LENGTH] &&
             !headers['Transfer-Encoding'] &&
             body.respond_to?(:to_ary)

            obody = body
            body, length = [], 0
            obody.each { |part| body << part; length += bytesize(part) }

            body = BodyProxy.new(body) do
              obody.close if obody.respond_to?(:close)
            end

            headers[CONTENT_LENGTH] = length.to_s
          end

          [status, headers, body]
        end