// an error.
func readDirFn(dirPath string, filter func(name string, typ os.FileMode) error) error {
	// Ensure we don't pick up files as directories.
	globAll := filepath.Clean(dirPath) + `\*`
	globAllP, err := syscall.UTF16PtrFromString(globAll)
	if err != nil {
		return errInvalidArgument
	}
	data := &syscall.Win32finddata{}
	handle, err := syscall.FindFirstFile(globAllP, data)
	if err != nil {

func IsLikelyMountPoint(path string) bool {
	path = filepath.Dir(path)
	if v, ok := mountPointCache.Load(path); ok {
		if b, ok := v.(bool); ok {
			return b
		}
	}
	wpath, _ := windows.UTF16PtrFromString(path)
	wvolume := make([]uint16, len(path)+1)

	if err := windows.GetVolumePathName(wpath, &wvolume[0], uint32(len(wvolume))); err != nil {
		mountPointCache.Store(path, false)
		return false
	}

// acls is out of scope here.
func Open(path string, flag int, perm os.FileMode) (*os.File, error) {
	if path == "" {
		return nil, syscall.ERROR_FILE_NOT_FOUND
	}

	pathp, err := syscall.UTF16PtrFromString(fixLongPath(path))
	if err != nil {
		return nil, err
	}

	var access uint32
	switch flag {
	case syscall.O_RDONLY:
		access = syscall.GENERIC_READ
	case syscall.O_WRONLY: