/
hash_function.go
156 lines (128 loc) · 2.59 KB
/
hash_function.go
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package mm128
import (
"encoding/binary"
"github.com/keyto1995/hashing/hashcode"
"github.com/keyto1995/hashing/interfaces"
"math/bits"
"unsafe"
)
const (
chunkSize = 16
c1 uint64 = 0x87c37b91114253d5
c2 uint64 = 0x4cf5ad432745937f
)
// Zhf seed为0的HashFunction
var Zhf = NewHashFunction(0)
type HashFunction struct {
seed uint32
}
func NewHashFunction(seed uint32) interfaces.HashFunction {
return &HashFunction{seed: seed}
}
func (hf *HashFunction) NewHasher() interfaces.Hasher {
return NewHasher(hf.seed)
}
func (hf *HashFunction) HashString(data string) hashcode.HashCode {
bs := []byte(data)
return hf.HashBytes(bs)
}
func (hf *HashFunction) HashBytes(data []byte) hashcode.HashCode {
n := len(data)
h1, h2 := uint64(hf.seed), uint64(hf.seed)
var k1, k2 uint64
nblocks := len(data) / chunkSize
for i := 0; i < nblocks; i++ {
t := (*[2]uint64)(unsafe.Pointer(&data[i*16]))
k1, k2 = t[0], t[1]
h1 ^= mixK1(k1)
h1 = bits.RotateLeft64(h1, 27)
h1 += h2
h1 = h1*5 + 0x52dce729
h2 ^= mixK2(k2)
h2 = bits.RotateLeft64(h2, 31)
h2 += h1
h2 = h2*5 + 0x38495ab5
}
k1, k2 = 0, 0
tail := data[nblocks*chunkSize:]
switch len(tail) % chunkSize {
case 15:
k2 ^= uint64(tail[14]) << 48
fallthrough
case 14:
k2 ^= uint64(tail[13]) << 40
fallthrough
case 13:
k2 ^= uint64(tail[12]) << 32
fallthrough
case 12:
k2 ^= uint64(tail[11]) << 24
fallthrough
case 11:
k2 ^= uint64(tail[10]) << 16
fallthrough
case 10:
k2 ^= uint64(tail[9]) << 8
fallthrough
case 9:
k2 ^= uint64(tail[8]) << 0
h2 ^= mixK2(k2)
fallthrough
case 8:
k1 ^= uint64(tail[7]) << 56
fallthrough
case 7:
k1 ^= uint64(tail[6]) << 48
fallthrough
case 6:
k1 ^= uint64(tail[5]) << 40
fallthrough
case 5:
k1 ^= uint64(tail[4]) << 32
fallthrough
case 4:
k1 ^= uint64(tail[3]) << 24
fallthrough
case 3:
k1 ^= uint64(tail[2]) << 16
fallthrough
case 2:
k1 ^= uint64(tail[1]) << 8
fallthrough
case 1:
k1 ^= uint64(tail[0]) << 0
h1 ^= mixK1(k1)
}
h1 ^= uint64(n)
h2 ^= uint64(n)
h1 += h2
h2 += h1
h1 = fmix64(h1)
h2 = fmix64(h2)
h1 += h2
h2 += h1
var b = make([]byte, chunkSize)
binary.LittleEndian.PutUint64(b[0:8], h1)
binary.LittleEndian.PutUint64(b[8:16], h2)
return hashcode.NewBytesHashCode(b)
}
func mixK1(k1 uint64) uint64 {
k1 *= c1
k1 = bits.RotateLeft64(k1, 31)
k1 *= c2
return k1
}
func mixK2(k2 uint64) uint64 {
k2 *= c2
k2 = bits.RotateLeft64(k2, 33)
k2 *= c1
return k2
}
func fmix64(k uint64) uint64 {
k ^= k >> 33
k *= 0xff51afd7ed558ccd
k ^= k >> 33
k *= 0xc4ceb9fe1a85ec53
k ^= k >> 33
return k
}