dirIdx  int // entries[:dirIdx] have already been returned in ReadDirent
	pos     int64
	seeked  bool
}

var filesMu sync.Mutex
var files = map[int]*jsFile{
	0: {},
	1: {},
	2: {},
}

func fdToFile(fd int) (*jsFile, error) {
	filesMu.Lock()
	f, ok := files[fd]
	filesMu.Unlock()
	if !ok {
		return nil, EBADF
	}
	return f, nil
}

func Open(path string, openmode int, perm uint32) (int, error) {