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|
package murmur3
import (
"hash"
"math/bits"
)
const (
c1_128 = 0x87c37b91114253d5
c2_128 = 0x4cf5ad432745937f
)
// Make sure interfaces are correctly implemented.
var (
_ hash.Hash = new(digest128)
_ Hash128 = new(digest128)
_ bmixer = new(digest128)
)
// Hash128 provides an interface for a streaming 128 bit hash.
type Hash128 interface {
hash.Hash
Sum128() (uint64, uint64)
}
// digest128 represents a partial evaluation of a 128 bites hash.
type digest128 struct {
digest
seed1 uint64
seed2 uint64
h1 uint64 // Unfinalized running hash part 1.
h2 uint64 // Unfinalized running hash part 2.
}
// SeedNew128 returns a Hash128 for streaming 128 bit sums with its internal
// digests initialized to seed1 and seed2.
//
// The canonical implementation allows one only uint32 seed; to imitate that
// behavior, use the same, uint32-max seed for seed1 and seed2.
func SeedNew128(seed1, seed2 uint64) Hash128 {
d := &digest128{seed1: seed1, seed2: seed2}
d.bmixer = d
d.Reset()
return d
}
// New128 returns a Hash128 for streaming 128 bit sums.
func New128() Hash128 {
return SeedNew128(0, 0)
}
func (d *digest128) Size() int { return 16 }
func (d *digest128) reset() { d.h1, d.h2 = d.seed1, d.seed2 }
func (d *digest128) Sum(b []byte) []byte {
h1, h2 := d.Sum128()
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
for len(p) >= 16 {
k1 := uint64(p[0]) | uint64(p[1])<<8 | uint64(p[2])<<16 | uint64(p[3])<<24 | uint64(p[4])<<32 | uint64(p[5])<<40 | uint64(p[6])<<48 | uint64(p[7])<<56
k2 := uint64(p[8]) | uint64(p[9])<<8 | uint64(p[10])<<16 | uint64(p[11])<<24 | uint64(p[12])<<32 | uint64(p[13])<<40 | uint64(p[14])<<48 | uint64(p[15])<<56
p = p[16:]
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
return p
}
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 = bits.RotateLeft64(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 = bits.RotateLeft64(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
}
|
