func (w *Writer) WriteFloat64(f float64) {
	if w.err != nil {
		return
	}
	bits := math.Float64bits(f)
	binary.LittleEndian.PutUint64(w.b[:8], bits)
	w.wr.Write(w.b[:8])
}
func (w *Writer) WriteFloat64(f float64) {
	if w.err != nil {
		return
	}
	bits := math.Float64bits(f)
	binary.LittleEndian.PutUint64(w.b[:8], bits)
	w.wr.Write(w.b[:8])
}
// WriteFloat64 writes a float64.