Feature: add load-balance group

common/murmur3/murmur.go

@@ -0,0 +1,50 @@
+package murmur3
+
+type bmixer interface {
+	bmix(p []byte) (tail []byte)
+	Size() (n int)
+	reset()
+}
+
+type digest struct {
+	clen int      // Digested input cumulative length.
+	tail []byte   // 0 to Size()-1 bytes view of `buf'.
+	buf  [16]byte // Expected (but not required) to be Size() large.
+	seed uint32   // Seed for initializing the hash.
+	bmixer
+}
+
+func (d *digest) BlockSize() int { return 1 }
+
+func (d *digest) Write(p []byte) (n int, err error) {
+	n = len(p)
+	d.clen += n
+
+	if len(d.tail) > 0 {
+		// Stick back pending bytes.
+		nfree := d.Size() - len(d.tail) // nfree ∈ [1, d.Size()-1].
+		if nfree < len(p) {
+			// One full block can be formed.
+			block := append(d.tail, p[:nfree]...)
+			p = p[nfree:]
+			_ = d.bmix(block) // No tail.
+		} else {
+			// Tail's buf is large enough to prevent reallocs.
+			p = append(d.tail, p...)
+		}
+	}
+
+	d.tail = d.bmix(p)
+
+	// Keep own copy of the 0 to Size()-1 pending bytes.
+	nn := copy(d.buf[:], d.tail)
+	d.tail = d.buf[:nn]
+
+	return n, nil
+}
+
+func (d *digest) Reset() {
+	d.clen = 0
+	d.tail = nil
+	d.bmixer.reset()
+}

common/murmur3/murmur32.go

@@ -0,0 +1,149 @@
+package murmur3
+
+// https://github.com/spaolacci/murmur3/blob/master/murmur32.go
+
+import (
+	"hash"
+	"unsafe"
+)
+
+// Make sure interfaces are correctly implemented.
+var (
+	_ hash.Hash32 = new(digest32)
+	_ bmixer      = 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
+	h1 uint32 // Unfinalized running hash.
+}
+
+// New32 returns new 32-bit hasher
+func New32() hash.Hash32 { return New32WithSeed(0) }
+
+// New32WithSeed returns new 32-bit hasher set with explicit seed value
+func New32WithSeed(seed uint32) hash.Hash32 {
+	d := new(digest32)
+	d.seed = seed
+	d.bmixer = d
+	d.Reset()
+	return d
+}
+
+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
+
+	nblocks := len(p) / 4
+	for i := 0; i < nblocks; i++ {
+		k1 := *(*uint32)(unsafe.Pointer(&p[i*4]))
+
+		k1 *= c1_32
+		k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
+		k1 *= c2_32
+
+		h1 ^= k1
+		h1 = (h1 << 13) | (h1 >> 19) // rotl32(h1, 13)
+		h1 = h1*4 + h1 + 0xe6546b64
+	}
+	d.h1 = h1
+	return p[nblocks*d.Size():]
+}
+
+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 = (k1 << 15) | (k1 >> 17) // rotl32(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
+}
+
+func Sum32(data []byte) uint32 { return Sum32WithSeed(data, 0) }
+
+func Sum32WithSeed(data []byte, seed uint32) uint32 {
+	h1 := seed
+
+	nblocks := len(data) / 4
+	var p uintptr
+	if len(data) > 0 {
+		p = uintptr(unsafe.Pointer(&data[0]))
+	}
+	p1 := p + uintptr(4*nblocks)
+	for ; p < p1; p += 4 {
+		k1 := *(*uint32)(unsafe.Pointer(p))
+
+		k1 *= c1_32
+		k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
+		k1 *= c2_32
+
+		h1 ^= k1
+		h1 = (h1 << 13) | (h1 >> 19) // rotl32(h1, 13)
+		h1 = h1*4 + h1 + 0xe6546b64
+	}
+
+	tail := data[nblocks*4:]
+
+	var k1 uint32
+	switch len(tail) & 3 {
+	case 3:
+		k1 ^= uint32(tail[2]) << 16
+		fallthrough
+	case 2:
+		k1 ^= uint32(tail[1]) << 8
+		fallthrough
+	case 1:
+		k1 ^= uint32(tail[0])
+		k1 *= c1_32
+		k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
+		k1 *= c2_32
+		h1 ^= k1
+	}
+
+	h1 ^= uint32(len(data))
+
+	h1 ^= h1 >> 16
+	h1 *= 0x85ebca6b
+	h1 ^= h1 >> 13
+	h1 *= 0xc2b2ae35
+	h1 ^= h1 >> 16
+
+	return h1
+}