xxhash_other.go raw

   1  //go:build (!amd64 && !arm64) || appengine || !gc || purego
   2  // +build !amd64,!arm64 appengine !gc purego
   3  
   4  package xxhash
   5  
   6  // Sum64 computes the 64-bit xxHash digest of b with a zero seed.
   7  func Sum64(b []byte) uint64 {
   8  	// A simpler version would be
   9  	//   d := New()
  10  	//   d.Write(b)
  11  	//   return d.Sum64()
  12  	// but this is faster, particularly for small inputs.
  13  
  14  	n := len(b)
  15  	var h uint64
  16  
  17  	if n >= 32 {
  18  		v1 := primes[0] + prime2
  19  		v2 := prime2
  20  		v3 := uint64(0)
  21  		v4 := -primes[0]
  22  		for len(b) >= 32 {
  23  			v1 = round(v1, u64(b[0:8:len(b)]))
  24  			v2 = round(v2, u64(b[8:16:len(b)]))
  25  			v3 = round(v3, u64(b[16:24:len(b)]))
  26  			v4 = round(v4, u64(b[24:32:len(b)]))
  27  			b = b[32:len(b):len(b)]
  28  		}
  29  		h = rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
  30  		h = mergeRound(h, v1)
  31  		h = mergeRound(h, v2)
  32  		h = mergeRound(h, v3)
  33  		h = mergeRound(h, v4)
  34  	} else {
  35  		h = prime5
  36  	}
  37  
  38  	h += uint64(n)
  39  
  40  	for ; len(b) >= 8; b = b[8:] {
  41  		k1 := round(0, u64(b[:8]))
  42  		h ^= k1
  43  		h = rol27(h)*prime1 + prime4
  44  	}
  45  	if len(b) >= 4 {
  46  		h ^= uint64(u32(b[:4])) * prime1
  47  		h = rol23(h)*prime2 + prime3
  48  		b = b[4:]
  49  	}
  50  	for ; len(b) > 0; b = b[1:] {
  51  		h ^= uint64(b[0]) * prime5
  52  		h = rol11(h) * prime1
  53  	}
  54  
  55  	h ^= h >> 33
  56  	h *= prime2
  57  	h ^= h >> 29
  58  	h *= prime3
  59  	h ^= h >> 32
  60  
  61  	return h
  62  }
  63  
  64  func writeBlocks(d *Digest, b []byte) int {
  65  	v1, v2, v3, v4 := d.v1, d.v2, d.v3, d.v4
  66  	n := len(b)
  67  	for len(b) >= 32 {
  68  		v1 = round(v1, u64(b[0:8:len(b)]))
  69  		v2 = round(v2, u64(b[8:16:len(b)]))
  70  		v3 = round(v3, u64(b[16:24:len(b)]))
  71  		v4 = round(v4, u64(b[24:32:len(b)]))
  72  		b = b[32:len(b):len(b)]
  73  	}
  74  	d.v1, d.v2, d.v3, d.v4 = v1, v2, v3, v4
  75  	return n - len(b)
  76  }
  77