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internal/bloom/murmur128.go

@@ -0,0 +1,182 @@
+package bloom
+
+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
+}