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package murmur3
import (
//"encoding/binary"
"hash"
"unsafe"
)
const (
c1_128 = 0x87c37b91114253d5
c2_128 = 0x4cf5ad432745937f
)
// Make sure interfaces are correctly implemented.
var (
_ hash.Hash = new(digest128)
_ Hash128 = new(digest128)
_ bmixer = new(digest128)
)
// Hack: the standard api doesn't define any Hash128 interface.
type Hash128 interface {
hash.Hash
Sum128() (uint64, uint64)
}
// digest128 represents a partial evaluation of a 128 bites hash.
type digest128 struct {
digest
h1 uint64 // Unfinalized running hash part 1.
h2 uint64 // Unfinalized running hash part 2.
}
func New128() Hash128 {
d := new(digest128)
d.bmixer = d
d.Reset()
return d
}
func (d *digest128) Size() int { return 16 }
func (d *digest128) reset() { d.h1, d.h2 = 1, 1 }
func (d *digest128) Sum(b []byte) []byte {
h1, h2 := d.h1, d.h2
return append(b,
byte(h1>>56), byte(h1>>48), byte(h1>>40), byte(h1>>32),
byte(h1>>24), byte(h1>>16), byte(h1>>8), byte(h1),
byte(h2>>56), byte(h2>>48), byte(h2>>40), byte(h2>>32),
byte(h2>>24), byte(h2>>16), byte(h2>>8), byte(h2),
)
}
func (d *digest128) bmix(p []byte) (tail []byte) {
h1, h2 := d.h1, d.h2
nblocks := len(p) / 16
for i := 0; i < nblocks; i++ {
t := (*[2]uint64)(unsafe.Pointer(&p[i*16]))
k1, k2 := t[0], t[1]
k1 *= c1_128
k1 = (k1 << 31) | (k1 >> 33) // rotl64(k1, 31)
k1 *= c2_128
h1 ^= k1
h1 = (h1 << 27) | (h1 >> 37) // rotl64(h1, 27)
h1 += h2
h1 = h1*5 + 0x52dce729
k2 *= c2_128
k2 = (k2 << 33) | (k2 >> 31) // rotl64(k2, 33)
k2 *= c1_128
h2 ^= k2
h2 = (h2 << 31) | (h2 >> 33) // rotl64(h2, 31)
h2 += h1
h2 = h2*5 + 0x38495ab5
}
d.h1, d.h2 = h1, h2
return p[nblocks*d.Size():]
}
func (d *digest128) Sum128() (h1, h2 uint64) {
h1, h2 = d.h1, d.h2
var k1, k2 uint64
switch len(d.tail) & 15 {
case 15:
k2 ^= uint64(d.tail[14]) << 48
fallthrough
case 14:
k2 ^= uint64(d.tail[13]) << 40
fallthrough
case 13:
k2 ^= uint64(d.tail[12]) << 32
fallthrough
case 12:
k2 ^= uint64(d.tail[11]) << 24
fallthrough
case 11:
k2 ^= uint64(d.tail[10]) << 16
fallthrough
case 10:
k2 ^= uint64(d.tail[9]) << 8
fallthrough
case 9:
k2 ^= uint64(d.tail[8]) << 0
k2 *= c2_128
k2 = (k2 << 33) | (k2 >> 31) // rotl64(k2, 33)
k2 *= c1_128
h2 ^= k2
fallthrough
case 8:
k1 ^= uint64(d.tail[7]) << 56
fallthrough
case 7:
k1 ^= uint64(d.tail[6]) << 48
fallthrough
case 6:
k1 ^= uint64(d.tail[5]) << 40
fallthrough
case 5:
k1 ^= uint64(d.tail[4]) << 32
fallthrough
case 4:
k1 ^= uint64(d.tail[3]) << 24
fallthrough
case 3:
k1 ^= uint64(d.tail[2]) << 16
fallthrough
case 2:
k1 ^= uint64(d.tail[1]) << 8
fallthrough
case 1:
k1 ^= uint64(d.tail[0]) << 0
k1 *= c1_128
k1 = (k1 << 31) | (k1 >> 33) // rotl64(k1, 31)
k1 *= c2_128
h1 ^= k1
}
h1 ^= uint64(d.clen)
h2 ^= uint64(d.clen)
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 rotl64(x uint64, r byte) uint64 {
return (x << r) | (x >> (64 - r))
}
*/
// Sum128 returns the MurmurHash3 sum of data. It is equivalent to the
// following sequence (without the extra burden and the extra allocation):
// hasher := New128()
// hasher.Write(data)
// return hasher.Sum128()
func Sum128(data []byte) (h1 uint64, h2 uint64) {
d := &digest128{h1: 1, h2: 1}
d.tail = d.bmix(data)
d.clen = len(data)
return d.Sum128()
}
|