# File lib/rack/content_length.rb, line 13
    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) }
        obody.close if obody.respond_to?(:close)

        headers['Content-Length'] = length.to_s
      end

      [status, headers, body]
    end