public static function tempnam($dir, $prefix, $cb)
    {
        $cb = CallbackWrapper::forceWrap($cb);
        if (!FileSystem::$supported) {
            FileSystem::open(tempnam($dir, $prefix), 'w!', $cb);
        }
        $tries = 0;
        static::tempnamHandler($dir, $prefix, $cb, $tries);
    }