You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: untar.go
    path of file: ./repos/k3s/pkg/untar
    
    the code of the file until where you have to start completion: // Copyright 2017 The Go Authors. All rights reser
    
func untar(r io.Reader, dir string) (err error) {
	t0 := time.Now()
	nFiles := 0
	madeDir := map[string]bool{}
	defer func() {
		td := time.Since(t0)
		if err != nil {
			logrus.Printf("error extracting tarball into %s after %d files, %d dirs, %v: %v", dir, nFiles, len(madeDir), td, err)
		}
	}()
	zr, err := zstd.NewReader(r, zstd.WithDecoderMaxMemory(tarfile.MaxDecoderMemory))
	if err != nil {
		return fmt.Errorf("error extracting zstd-compressed body: %v", err)
	}
	defer zr.Close()
	tr := tar.NewReader(zr)
	loggedChtimesError := false
	for {
		f, err := tr.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			logrus.Printf("tar reading error: %v", err)
			return fmt.Errorf("tar error: %v", err)
		}
		if !validRelPath(f.Name) {
			return fmt.Errorf("tar contained invalid name error %q", f.Name)
		}
		rel := filepath.FromSlash(f.Name)
		abs := filepath.Join(dir, rel)

		fi := f.FileInfo()
		mode := fi.Mode()
		switch {
		case mode.IsRegular():
			// Make the directory. This is redundant because it should
			// already be made by a directory entry in the tar
			// beforehand. Thus, don't check for errors; the next
			// write will fail with the same error.
			dir := filepath.Dir(abs)
			if !madeDir[dir] {
				if err := os.MkdirAll(filepath.Dir(abs), 0755); err != nil {
					return err
				}
				madeDir[dir] = true
			}
			wf, err := os.OpenFile(abs, os.O_RDWR|os.O_CREATE|os.O_TRUNC, mode.Perm())
			if err != nil {
				return err
			}
			n, err := io.Copy(wf, tr)
			if closeErr := wf.Close(); closeErr != nil && err == nil {
				err = closeErr
			}
			if err != nil {
				return fmt.Errorf("error writing to %s: %v", abs, err)
			}
			if n != f.Size {
				return fmt.Errorf("only wrote %d bytes to %s; expected %d", n, abs, f.Size)
			}
			modTime := f.ModTime
			if modTime.After(t0) {
				// Clamp modtimes at system time. See
				// golang.org/issue/19062 when clock on
				// buildlet was behind the gitmirror server
				// doing the git-archive.
				modTime = t0
			}
			if !modTime.IsZero() {
				if err := os.Chtimes(abs, modTime, modTime); err != nil && !loggedChtimesError {
					// benign error. Gerrit doesn't even set the
					// modtime in these, and we don't end up relying
					// on it anywhere (the gomote push command relies
					// on digests only), so this is a little pointless
					// for now.
					logrus.Printf("error changing modtime: %v (further Chtimes errors suppressed)", err)
					loggedChtimesError = true // once is enough
				}
			}
			nFiles++
		case mode.IsDir():
			if err := os.MkdirAll(abs, 0755); err != nil {
				return err
			}
			madeDir[abs] = true
		case f.Linkname != "":
			if err := os.Symlink(f.Linkname, abs); err != nil {
				return err
			}
		default:
			return fmt.Errorf("tar file entry %s contained unsupported file type %v", f.Name, mode)
		}
	}
	return nil
}