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murmur.go
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murmur.go
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package gostatix
import (
"math/bits"
"unsafe"
)
const (
c1_128 = 0x87c37b91114253d5
c2_128 = 0x4cf5ad432745937f
block_size = 16
)
type digest128 struct {
h1 uint64
h2 uint64
}
func (d *digest128) bmix(p []byte, nblocks int) {
h1, h2 := d.h1, d.h2
for i := 0; i < nblocks; i++ {
t := (*[2]uint64)(unsafe.Pointer(&p[i*16]))
k1, k2 := t[0], t[1]
k1 *= c1_128
k1 = bits.RotateLeft64(k1, 31)
k1 *= c2_128
h1 ^= k1
h1 = bits.RotateLeft64(h1, 27)
h1 += h2
h1 = h1*5 + 0x52dce729
k2 *= c2_128
k2 = bits.RotateLeft64(k2, 33)
k2 *= c1_128
h2 ^= k2
h2 = bits.RotateLeft64(h2, 31)
h2 += h1
h2 = h2*5 + 0x38495ab5
}
d.h1, d.h2 = h1, h2
}
func (d *digest128) Size() int { return 16 }
func (d *digest128) Sum128(tail []byte, dlen uint) (h1, h2 uint64) {
h1, h2 = d.h1, d.h2
var k1, k2 uint64
switch len(tail) & 15 {
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
k2 *= c2_128
k2 = bits.RotateLeft64(k2, 33)
k2 *= c1_128
h2 ^= 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
k1 *= c1_128
k1 = bits.RotateLeft64(k1, 31)
k1 *= c2_128
h1 ^= k1
}
h1 ^= uint64(dlen)
h2 ^= uint64(dlen)
h1 += h2
h2 += h1
h1 = fmix64(h1)
h2 = fmix64(h2)
h1 += h2
h2 += h1
return h1, h2
}
func fmix64(k uint64) uint64 {
k ^= k >> 33
k *= 0xff51afd7ed558ccd
k ^= k >> 33
k *= 0xc4ceb9fe1a85ec53
k ^= k >> 33
return k
}
func sum128(data []byte) (h1 uint64, h2 uint64) {
d := digest128{h1: 0, h2: 0}
dlen := len(data)
nblocks := dlen / 16
d.bmix(data, nblocks)
tail := data[nblocks*d.Size():]
return d.Sum128(tail, uint(dlen))
}