# File lib/rack/file.rb, line 34
    def _call(env)
      @path_info = Utils.unescape(env["PATH_INFO"])
      parts = @path_info.split SEPS

      return fail(403, "Forbidden")  if parts.include? ".."

      @path = F.join(@root, *parts)

      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