# File lib/rack/conditionalget.rb, line 22
    def call(env)
      return @app.call(env) unless %w[GET HEAD].include?(env['REQUEST_METHOD'])

      status, headers, body = @app.call(env)
      headers = Utils::HeaderHash.new(headers)
      if etag_matches?(env, headers) || modified_since?(env, headers)
        status = 304
        headers.delete('Content-Type')
        headers.delete('Content-Length')
        body = []
      end
      [status, headers, body]
    end