// FileInfo fields.
	if sys, ok := fi.Sys().(*Header); ok {
		// This FileInfo came from a Header (not the OS). Use the
		// original Header to populate all remaining fields.
		h.Uid = sys.Uid
		h.Gid = sys.Gid
		h.Uname = sys.Uname
		h.Gname = sys.Gname
		h.AccessTime = sys.AccessTime
		h.ChangeTime = sys.ChangeTime
		if sys.Xattrs != nil {
			h.Xattrs = make(map[string]string)

pkg archive/tar, type FileInfoNames interface { Gname, IsDir, ModTime, Mode, Name, Size, Sys, Uname } #50102
pkg archive/tar, type FileInfoNames interface, Gname() (string, error) #50102
pkg archive/tar, type FileInfoNames interface, IsDir() bool #50102
pkg archive/tar, type FileInfoNames interface, ModTime() time.Time #50102
pkg archive/tar, type FileInfoNames interface, Mode() fs.FileMode #50102
pkg archive/tar, type FileInfoNames interface, Name() string #50102

	}
	if got, want := fh2.ModifiedDate, fh.ModifiedDate; got != want {
		t.Errorf("ModifiedDate: got %d, want %d\n", got, want)
	}

	if sysfh, ok := fi.Sys().(*FileHeader); !ok && sysfh != fh {
		t.Errorf("Sys didn't return original *FileHeader")
	}
}

func TestFileHeaderRoundTrip(t *testing.T) {
	fh := &FileHeader{
		Name:             "foo.txt",
		UncompressedSize: 987654321,

		}
	}
}

func TestWriterAddFS(t *testing.T) {
	fsys := fstest.MapFS{
		"file.go":              {Data: []byte("hello")},
		"subfolder/another.go": {Data: []byte("world")},
	}
	var buf bytes.Buffer
	tw := NewWriter(&buf)
	if err := tw.AddFS(fsys); err != nil {
		t.Fatal(err)
	}

	// Test that we can get the files back from the archive

// It walks the directory tree starting at the root of the filesystem
// adding each file to the zip using deflate while maintaining the directory structure.
func (w *Writer) AddFS(fsys fs.FS) error {
	return fs.WalkDir(fsys, ".", func(name string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if d.IsDir() {
			return nil
		}
		info, err := d.Info()
		if err != nil {

		}
		if got, want := h2.ModTime, v.h.ModTime; got != want {
			t.Errorf("i=%d: ModTime: got %v, want %v", i, got, want)
		}
		if sysh, ok := fi.Sys().(*Header); !ok || sysh != v.h {
			t.Errorf("i=%d: Sys didn't return original *Header", i)
		}
	}
}

func TestHeaderAllowedFormats(t *testing.T) {
	vectors := []struct {
		header  *Header           // Input header

var userMap, groupMap sync.Map // map[int]string

func statUnix(fi fs.FileInfo, h *Header, doNameLookups bool) error {
	sys, ok := fi.Sys().(*syscall.Stat_t)
	if !ok {
		return nil
	}
	h.Uid = int(sys.Uid)
	h.Gid = int(sys.Gid)
	if doNameLookups {
		// Best effort at populating Uname and Gname.
		// The os/user functions may fail for any number of reasons