code: func (xxh *xxHash) Sum32() uint32 {
  	h32 := uint32(xxh.totalLen)
  	if xxh.totalLen >= 16 {
  		h32 += rol1(xxh.v1) + rol7(xxh.v2) + rol12(xxh.v3) + rol18(xxh.v4)
  	} else {
  		h32 += xxh.seed + prime32_5
  	}
  
  	p := 0
  	n := xxh.bufused
  	for n := n - 4; p <= n; p += 4 {
  		h32 += u32(xxh.buf[p:p+4]) * prime32_3
  		h32 = rol17(h32) * prime32_4
  	}
  	for ; p < n; p++ {
  		h32 += uint32(xxh.buf[p]) * prime32_5
  		h32 = rol11(h32) * prime32_1
  	}
  
  	h32 ^= h32 >> 15
  	h32 *= prime32_2
  	h32 ^= h32 >> 13
  	h32 *= prime32_3
  	h32 ^= h32 >> 16
  
  	return h32
  }
docs: // Sum32 returns the 32 bits Hash value.