file, err := os.CreateTemp(fs.prefix(dir), prefix)
	if err != nil {
		return nil, err
	}
	return &defaultFile{file}, nil
}

// ReadDir via os.ReadDir
func (fs *DefaultFs) ReadDir(dirname string) ([]os.DirEntry, error) {
	return os.ReadDir(fs.prefix(dirname))
}

// Walk via filepath.Walk
func (fs *DefaultFs) Walk(root string, walkFn filepath.WalkFunc) error {

	xCondAddrSize // switch on address size
	xCondIsMem    // switch on memory vs register argument

	xSetOp // set instruction opcode

	xReadSlashR // read /r
	xReadIb     // read ib
	xReadIw     // read iw
	xReadId     // read id
	xReadIo     // read io
	xReadCb     // read cb
	xReadCw     // read cw
	xReadCd     // read cd
	xReadCp     // read cp
	xReadCm     // read cm

	xArg1            // arg 1

			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)

	if roots.len() > 0 || firstErr == nil {
		return roots, nil
	}

	return nil, firstErr
}

// readUniqueDirectoryEntries is like os.ReadDir but omits
// symlinks that point within the directory.
func readUniqueDirectoryEntries(dir string) ([]fs.DirEntry, error) {
	files, err := os.ReadDir(dir)
	if err != nil {
		return nil, err
	}
	uniq := files[:0]
	for _, f := range files {
		if !isSameDirSymlink(f, dir) {

	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.
	//

			// 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)

// 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":

// The only possible returned error is [path.ErrBadPattern], reporting that
// the pattern is malformed.
//
// If fs implements [GlobFS], Glob calls fs.Glob.
// Otherwise, Glob uses [ReadDir] to traverse the directory tree
// and look for matches for the pattern.
func Glob(fsys FS, pattern string) (matches []string, err error) {
	return globWithLimit(fsys, pattern, 0)
}

		if osErrToFileErr(err) == errFileNotFound {
			return nil
		}
		return osErrToFileErr(err)
	}
	defer d.Close()

	maxEntries := 1000
	for {
		// Read up to max number of entries.
		fis, err := d.Readdir(maxEntries)
		if err != nil {
			if err == io.EOF {
				break
			}
			err = osErrToFileErr(err)
			if err == errFileNotFound {
				return nil
			}
			return err
		}
		for _, fi := range fis {