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package murmur3
import (
"hash"
"math/bits"
)
// Make sure interfaces are correctly implemented.
var (
_ hash.Hash = new(digest32)
_ hash.Hash32 = 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
seed uint32
h1 uint32 // Unfinalized running hash.
}
// SeedNew32 returns a hash.Hash32 for streaming 32 bit sums with its internal
// digest initialized to seed.
//
// This reads and processes the data in chunks of little endian uint32s;
// thus, the returned hash is portable across architectures.
func SeedNew32(seed uint32) hash.Hash32 {
d := &digest32{seed: seed}
d.bmixer = d
d.Reset()
return d
}
// New32 returns a hash.Hash32 for streaming 32 bit sums.
func New32() hash.Hash32 {
return SeedNew32(0)
}
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
for len(p) >= 4 {
k1 := uint32(p[0]) | uint32(p[1])<<8 | uint32(p[2])<<16 | uint32(p[3])<<24
p = p[4:]
k1 *= c1_32
k1 = bits.RotateLeft32(k1, 15)
k1 *= c2_32
h1 ^= k1
h1 = bits.RotateLeft32(h1, 13)
h1 = h1*5 + 0xe6546b64
}
d.h1 = h1
return p
}
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 = bits.RotateLeft32(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
}
|
