} else if err != nil {
		return false, fmt.Errorf("error reading profile header: %w", err)
	}

	return string(hdr) == serializationHeader, nil
}

// FromSerialized parses a profile from serialization output of Profile.WriteTo.
func FromSerialized(r io.Reader) (*Profile, error) {
	d := emptyProfile()

	scanner := bufio.NewScanner(r)
	scanner.Split(bufio.ScanLines)

	if !scanner.Scan() {

//
// Entries are sorted by "call edge weight", from highest to lowest.

const serializationHeader = "GO PREPROFILE V1\n"

// WriteTo writes a serialized representation of Profile to w.
//
// FromSerialized can parse the format back to Profile.
//
// WriteTo implements io.WriterTo.Write.
func (d *Profile) WriteTo(w io.Writer) (int64, error) {
	bw := bufio.NewWriter(w)

	var written int64

	// Header

	if err != nil {
		t.Fatalf("WriteTo got err %v want nil", err)
	}
	if n != int64(buf.Len()) {
		t.Errorf("WriteTo got n %d want %d", n, int64(buf.Len()))
	}

	b := buf.Bytes()

	got, err := FromSerialized(&buf)
	if err != nil {
		t.Fatalf("processSerialized got err %v want nil", err)
	}
	if err := equal(got, d); err != nil {
		t.Errorf("processSerialized output does not match input: %v", err)
	}

	return b