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.
package xxh32
import (
	"encoding/binary"
)
const (
	prime1 uint32 = 2654435761
	prime2 uint32 = 2246822519
	prime3 uint32 = 3266489917
	prime4 uint32 = 668265263
	prime5 uint32 = 374761393
	primeMask   = 0xFFFFFFFF
	prime1plus2 = uint32((uint64(prime1) + uint64(prime2)) & primeMask)  
	prime1minus = uint32((-int64(prime1)) & primeMask)                   
)
type XXHZero struct {
	v1       uint32
	v2       uint32
	v3       uint32
	v4       uint32
	totalLen uint64
	buf      [16]byte
	bufused  int
}