}

		dirs, err := ReadDir(sub, ".")
		if err != nil || len(dirs) != 1 || dirs[0].Name() != "goodbye.txt" {
			var names []string
			for _, d := range dirs {
				names = append(names, d.Name())
			}
			t.Errorf(`ReadDir(%s, ".") = %v, %v, want %v, nil`, desc, names, err, []string{"goodbye.txt"})
		}
	}

			t.Errorf("Glob(%s) = %v, %v, want %v, nil", desc, names, err, []string{"hello.txt"})
		}
	}

	// Test that ReadDir uses the method when present.
	names, err := Glob(globOnly{testFsys}, "*.txt")
	check("readDirOnly", names, err)

	// Test that ReadDir uses Open when the method is not present.
	names, err = Glob(openOnly{testFsys}, "*.txt")
	check("openOnly", names, err)

	if err != nil {
		return nil, err
	}
	file, err := f.fsys.Open(full)
	return file, f.fixErr(err)
}

func (f *subFS) ReadDir(name string) ([]DirEntry, error) {
	full, err := f.fullName("read", name)
	if err != nil {
		return nil, err
	}
	dir, err := ReadDir(f.fsys, full)
	return dir, f.fixErr(err)
}

func (f *subFS) ReadFile(name string) ([]byte, error) {
	full, err := f.fullName("read", name)

func isDirEmpty(dirname string, legacy bool) bool {
	if legacy {
		// On filesystems such as btrfs, nfs this is not true, so fallback
		// to performing readdir() instead.
		entries, err := readDirN(dirname, 1)
		if err != nil {
			return false
		}
		return len(entries) == 0
	}
	var stat syscall.Stat_t
	if err := syscall.Stat(dirname, &stat); err != nil {
		return false
	}

	if err != nil {
		return nil, err
	}
	return &shuffledFile{File: f}, nil
}

type shuffledFile struct{ fs.File }

func (f *shuffledFile) ReadDir(n int) ([]fs.DirEntry, error) {
	dirents, err := f.File.(fs.ReadDirFile).ReadDir(n)
	// Shuffle in a deterministic way, all we care about is making sure that the
	// list of directory entries is not is the lexicographic order.
	//

// given goroot and compiler.
func IsStandardPackage(goroot, compiler, path string) bool {
	switch compiler {
	case "gc":
		dir := filepath.Join(goroot, "src", path)
		dirents, err := os.ReadDir(dir)
		if err != nil {
			return false
		}
		for _, dirent := range dirents {
			if strings.HasSuffix(dirent.Name(), ".go") {
				return true
			}
		}
		return false
	case "gccgo":

			// Try a bigger buffer.
			t.Logf("ReadDirent: %v; retrying with larger buffer", err)
			buf = bytes.Repeat([]byte{0xCD}, len(buf)*2)
			continue
		}
		if err != nil {
			t.Fatalf("syscall.readdir: %v", err)
		}
		t.Logf("ReadDirent: read %d bytes", n)
		if n == 0 {
			break
		}

		var consumed, count int
		consumed, count, names = syscall.ParseDirent(buf[:n], -1, names)

	if file == nil {
		return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
	}
	if file.IsDir() {
		return &openDir{file, f.readDir(name), 0}, nil
	}
	return &openFile{file, 0}, nil
}

// ReadDir reads and returns the entire named directory.
func (f FS) ReadDir(name string) ([]fs.DirEntry, error) {
	file, err := f.Open(name)
	if err != nil {
		return nil, err
	}
	dir, ok := file.(*openDir)

	// Prefer to use ReadDir instead of Readdir,
	// because the former doesn't require calling
	// Stat on every entry of a directory on Unix.
	var dirs anyDirs
	var err error
	if d, ok := f.(fs.ReadDirFile); ok {
		var list dirEntryDirs
		list, err = d.ReadDir(-1)
		dirs = list
	} else {
		var list fileInfoDirs
		list, err = f.Readdir(-1)
		dirs = list
	}

	if err != nil {

// and uploading is supposed to be idempotent.)
func (u *uploader) findWork() work {
	localdir, uploaddir := u.dir.LocalDir(), u.dir.UploadDir()
	var ans work
	fis, err := os.ReadDir(localdir)
	if err != nil {
		u.logger.Printf("Could not find work: failed to read local dir %s: %v", localdir, err)
		return ans
	}

	mode, asof := u.dir.Mode()