# File lib/rack/file.rb, line 36
    def _call(env)
      unless ALLOWED_VERBS.include? env[REQUEST_METHOD]
        return fail(405, "Method Not Allowed", {'Allow' => ALLOW_HEADER})
      end

      path_info = Utils.unescape(env[PATH_INFO])
      clean_path_info = Utils.clean_path_info(path_info)

      @path = F.join(@root, clean_path_info)

      available = begin
        F.file?(@path) && F.readable?(@path)
      rescue SystemCallError
        false
      end

      if available
        serving(env)
      else
        fail(404, "File not found: #{path_info}")
      end
    end