1// +build !amd64 appengine !gc purego
2
3package xxhash
4
5// Sum64 computes the 64-bit xxHash digest of b.
6func Sum64(b []byte) uint64 {
7	// A simpler version would be
8	//   d := New()
9	//   d.Write(b)
10	//   return d.Sum64()
11	// but this is faster, particularly for small inputs.
12
13	n := len(b)
14	var h uint64
15
16	if n >= 32 {
17		v1 := prime1v + prime2
18		v2 := prime2
19		v3 := uint64(0)
20		v4 := -prime1v
21		for len(b) >= 32 {
22			v1 = round(v1, u64(b[0:8:len(b)]))
23			v2 = round(v2, u64(b[8:16:len(b)]))
24			v3 = round(v3, u64(b[16:24:len(b)]))
25			v4 = round(v4, u64(b[24:32:len(b)]))
26			b = b[32:len(b):len(b)]
27		}
28		h = rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
29		h = mergeRound(h, v1)
30		h = mergeRound(h, v2)
31		h = mergeRound(h, v3)
32		h = mergeRound(h, v4)
33	} else {
34		h = prime5
35	}
36
37	h += uint64(n)
38
39	i, end := 0, len(b)
40	for ; i+8 <= end; i += 8 {
41		k1 := round(0, u64(b[i:i+8:len(b)]))
42		h ^= k1
43		h = rol27(h)*prime1 + prime4
44	}
45	if i+4 <= end {
46		h ^= uint64(u32(b[i:i+4:len(b)])) * prime1
47		h = rol23(h)*prime2 + prime3
48		i += 4
49	}
50	for ; i < end; i++ {
51		h ^= uint64(b[i]) * 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
64func 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