# File lib/vendor/etag.rb, line 10
    def call(env)
      status, headers, body = @app.call(env)

      unless headers.key?('Etag')
        hashes = []
        body.each{|chunk| hashes << chunk.hash }
        headers['Etag'] = %("#{Digest::MD5.hexdigest(hashes.join)}")
      end

      [status, headers, body]
    end