func (xxh XXHZero) Sum(b []byte) []byte {
	h32 := xxh.Sum32()
	return append(b, byte(h32), byte(h32>>8), byte(h32>>16), byte(h32>>24))
}
func (xxh XXHZero) Sum(b []byte) []byte {
	h32 := xxh.Sum32()
	return append(b, byte(h32), byte(h32>>8), byte(h32>>16), byte(h32>>24))
}
// Sum appends the current hash to b and returns the resulting slice.
// It does not change the underlying hash state.