func (xx *XXHash32) Sum(in []byte) []byte {
	s := xx.Sum32()
	return append(in, byte(s>>24), byte(s>>16), byte(s>>8), byte(s))
}
func (xx *XXHash32) Sum(in []byte) []byte {
	s := xx.Sum32()
	return append(in, byte(s>>24), byte(s>>16), byte(s>>8), byte(s))
}
// Sum appends the current hash to b and returns the resulting slice.
// It does not change the underlying hash state.