File: murmur32.go

package info (click to toggle)
golang-github-spaolacci-murmur3 1.1-3
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, buster, sid
  • size: 96 kB
  • sloc: makefile: 2
file content (167 lines) | stat: -rw-r--r-- 3,363 bytes parent folder | download | duplicates (2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
package murmur3

// http://code.google.com/p/guava-libraries/source/browse/guava/src/com/google/common/hash/Murmur3_32HashFunction.java

import (
	"hash"
	"unsafe"
)

// Make sure interfaces are correctly implemented.
var (
	_ hash.Hash   = new(digest32)
	_ hash.Hash32 = new(digest32)
	_ bmixer      = new(digest32)
)

const (
	c1_32 uint32 = 0xcc9e2d51
	c2_32 uint32 = 0x1b873593
)

// digest32 represents a partial evaluation of a 32 bites hash.
type digest32 struct {
	digest
	h1 uint32 // Unfinalized running hash.
}

// New32 returns new 32-bit hasher
func New32() hash.Hash32 { return New32WithSeed(0) }

// New32WithSeed returns new 32-bit hasher set with explicit seed value
func New32WithSeed(seed uint32) hash.Hash32 {
	d := new(digest32)
	d.seed = seed
	d.bmixer = d
	d.Reset()
	return d
}

func (d *digest32) Size() int { return 4 }

func (d *digest32) reset() { d.h1 = d.seed }

func (d *digest32) Sum(b []byte) []byte {
	h := d.Sum32()
	return append(b, byte(h>>24), byte(h>>16), byte(h>>8), byte(h))
}

// Digest as many blocks as possible.
func (d *digest32) bmix(p []byte) (tail []byte) {
	h1 := d.h1

	nblocks := len(p) / 4
	for i := 0; i < nblocks; i++ {
		k1 := *(*uint32)(unsafe.Pointer(&p[i*4]))

		k1 *= c1_32
		k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
		k1 *= c2_32

		h1 ^= k1
		h1 = (h1 << 13) | (h1 >> 19) // rotl32(h1, 13)
		h1 = h1*4 + h1 + 0xe6546b64
	}
	d.h1 = h1
	return p[nblocks*d.Size():]
}

func (d *digest32) Sum32() (h1 uint32) {

	h1 = d.h1

	var k1 uint32
	switch len(d.tail) & 3 {
	case 3:
		k1 ^= uint32(d.tail[2]) << 16
		fallthrough
	case 2:
		k1 ^= uint32(d.tail[1]) << 8
		fallthrough
	case 1:
		k1 ^= uint32(d.tail[0])
		k1 *= c1_32
		k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
		k1 *= c2_32
		h1 ^= k1
	}

	h1 ^= uint32(d.clen)

	h1 ^= h1 >> 16
	h1 *= 0x85ebca6b
	h1 ^= h1 >> 13
	h1 *= 0xc2b2ae35
	h1 ^= h1 >> 16

	return h1
}

/*
func rotl32(x uint32, r byte) uint32 {
	return (x << r) | (x >> (32 - r))
}
*/

// Sum32 returns the MurmurHash3 sum of data. It is equivalent to the
// following sequence (without the extra burden and the extra allocation):
//     hasher := New32()
//     hasher.Write(data)
//     return hasher.Sum32()
func Sum32(data []byte) uint32 { return Sum32WithSeed(data, 0) }

// Sum32WithSeed returns the MurmurHash3 sum of data. It is equivalent to the
// following sequence (without the extra burden and the extra allocation):
//     hasher := New32WithSeed(seed)
//     hasher.Write(data)
//     return hasher.Sum32()
func Sum32WithSeed(data []byte, seed uint32) uint32 {

	h1 := seed

	nblocks := len(data) / 4
	var p uintptr
	if len(data) > 0 {
		p = uintptr(unsafe.Pointer(&data[0]))
	}
	p1 := p + uintptr(4*nblocks)
	for ; p < p1; p += 4 {
		k1 := *(*uint32)(unsafe.Pointer(p))

		k1 *= c1_32
		k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
		k1 *= c2_32

		h1 ^= k1
		h1 = (h1 << 13) | (h1 >> 19) // rotl32(h1, 13)
		h1 = h1*4 + h1 + 0xe6546b64
	}

	tail := data[nblocks*4:]

	var k1 uint32
	switch len(tail) & 3 {
	case 3:
		k1 ^= uint32(tail[2]) << 16
		fallthrough
	case 2:
		k1 ^= uint32(tail[1]) << 8
		fallthrough
	case 1:
		k1 ^= uint32(tail[0])
		k1 *= c1_32
		k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
		k1 *= c2_32
		h1 ^= k1
	}

	h1 ^= uint32(len(data))

	h1 ^= h1 >> 16
	h1 *= 0x85ebca6b
	h1 ^= h1 >> 13
	h1 *= 0xc2b2ae35
	h1 ^= h1 >> 16

	return h1
}