// during tests.
type OSInterface interface {
	MkdirAll(path string, perm os.FileMode) error
	Symlink(oldname string, newname string) error
	Stat(path string) (os.FileInfo, error)
	Remove(path string) error
	RemoveAll(path string) error
	Create(path string) (*os.File, error)
	Chmod(path string, perm os.FileMode) error
	Hostname() (name string, err error)
	Chtimes(path string, atime time.Time, mtime time.Time) error

	return readInt(buf, unsafe.Offsetof(syscall.Dirent{}.Namlen), unsafe.Sizeof(syscall.Dirent{}.Namlen))
}

func direntType(buf []byte) FileMode {
	off := unsafe.Offsetof(syscall.Dirent{}.Type)
	if off >= uintptr(len(buf)) {
		return ^FileMode(0) // unknown
	}
	typ := buf[off]
	switch typ {
	case syscall.DT_BLK:
		return ModeDevice
	case syscall.DT_CHR:
		return ModeDevice | ModeCharDevice

	return readInt(buf, unsafe.Offsetof(syscall.Dirent{}.Namlen), unsafe.Sizeof(syscall.Dirent{}.Namlen))
}

func direntType(buf []byte) FileMode {
	off := unsafe.Offsetof(syscall.Dirent{}.Type)
	if off >= uintptr(len(buf)) {
		return ^FileMode(0) // unknown
	}
	typ := buf[off]
	switch typ {
	case syscall.DT_BLK:
		return ModeDevice
	case syscall.DT_CHR:
		return ModeDevice | ModeCharDevice

	return readInt(buf, unsafe.Offsetof(syscall.Dirent{}.Namlen), unsafe.Sizeof(syscall.Dirent{}.Namlen))
}

func direntType(buf []byte) FileMode {
	off := unsafe.Offsetof(syscall.Dirent{}.Type)
	if off >= uintptr(len(buf)) {
		return ^FileMode(0) // unknown
	}
	switch syscall.Filetype(buf[off]) {
	case syscall.FILETYPE_BLOCK_DEVICE:
		return ModeDevice
	case syscall.FILETYPE_CHARACTER_DEVICE:

func (m FileMode) IsDir() bool {
	return m&ModeDir != 0
}

// IsRegular reports whether m describes a regular file.
// That is, it tests that no mode type bits are set.
func (m FileMode) IsRegular() bool {
	return m&ModeType == 0
}

// Perm returns the Unix permission bits in m (m & [ModePerm]).
func (m FileMode) Perm() FileMode {
	return m & ModePerm
}

// flags and shouldn't be considered as replacement
// for os.OpenFile().
func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
	return lockedOpenFile(path, flag, perm, 0)
}

// Open - Call os.OpenFile
func Open(path string, flag int, perm os.FileMode) (*os.File, error) {
	return os.OpenFile(path, flag, perm)

// flags and shouldn't be considered as replacement
// for os.OpenFile().
func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
	return lockedOpenFile(path, flag, perm, syscall.F_SETLKW)
}

// Open - Call os.OpenFile
func Open(path string, flag int, perm os.FileMode) (*os.File, error) {
	return os.OpenFile(path, flag, perm)

type formatTest struct {
	name    string
	size    int64
	mode    FileMode
	modTime time.Time
	isDir   bool
}

func (fs *formatTest) Name() string {
	return fs.name
}

func (fs *formatTest) Size() int64 {
	return fs.size
}

func (fs *formatTest) Mode() FileMode {
	return fs.mode
}

func (fs *formatTest) ModTime() time.Time {
	return fs.modTime
}

	return readInt(buf, unsafe.Offsetof(syscall.Dirent{}.Namlen), unsafe.Sizeof(syscall.Dirent{}.Namlen))
}

func direntType(buf []byte) FileMode {
	off := unsafe.Offsetof(syscall.Dirent{}.Type)
	if off >= uintptr(len(buf)) {
		return ^FileMode(0) // unknown
	}
	typ := buf[off]
	switch typ {
	case syscall.DT_BLK:
		return ModeDevice
	case syscall.DT_CHR:
		return ModeDevice | ModeCharDevice

	reclen, ok := direntReclen(buf)
	if !ok {
		return 0, false
	}
	return reclen - uint64(unsafe.Offsetof(syscall.Dirent{}.Name)), true
}

func direntType(buf []byte) FileMode {
	return ^FileMode(0) // unknown