Add msgpack wire protocol with halfsiphash checksums

lib/halfsiphash/halfsiphash.go

@@ -0,0 +1,74 @@
+package halfsiphash
+
+import "encoding/binary"
+
+func rotl(x uint32, b uint) uint32 {
+	return (x << b) | (x >> (32 - b))
+}
+
+func sipround(v0, v1, v2, v3 *uint32) {
+	*v0 += *v1
+	*v1 = rotl(*v1, 5)
+	*v1 ^= *v0
+	*v0 = rotl(*v0, 16)
+	*v2 += *v3
+	*v3 = rotl(*v3, 8)
+	*v3 ^= *v2
+	*v0 += *v3
+	*v3 = rotl(*v3, 7)
+	*v3 ^= *v0
+	*v2 += *v1
+	*v1 = rotl(*v1, 13)
+	*v1 ^= *v2
+	*v2 = rotl(*v2, 16)
+}
+
+// Sum32 computes HalfSipHash-2-4 with an 8-byte key and returns a 4-byte hash.
+func Sum32(data []byte, key [8]byte) uint32 {
+	k0 := binary.LittleEndian.Uint32(key[0:4])
+	k1 := binary.LittleEndian.Uint32(key[4:8])
+
+	v0 := uint32(0) ^ k0
+	v1 := uint32(0) ^ k1
+	v2 := uint32(0x6c796765) ^ k0
+	v3 := uint32(0x74656462) ^ k1
+
+	// Process full 4-byte blocks.
+	nblocks := len(data) / 4
+	for i := 0; i < nblocks; i++ {
+		m := binary.LittleEndian.Uint32(data[i*4:])
+		v3 ^= m
+		for j := 0; j < 2; j++ {
+			sipround(&v0, &v1, &v2, &v3)
+		}
+		v0 ^= m
+	}
+
+	// Process remaining bytes.
+	b := uint32(len(data)) << 24
+	tail := data[nblocks*4:]
+	switch len(tail) {
+	case 3:
+		b |= uint32(tail[2]) << 16
+		fallthrough
+	case 2:
+		b |= uint32(tail[1]) << 8
+		fallthrough
+	case 1:
+		b |= uint32(tail[0])
+	}
+
+	v3 ^= b
+	for i := 0; i < 2; i++ {
+		sipround(&v0, &v1, &v2, &v3)
+	}
+	v0 ^= b
+
+	v2 ^= 0xff
+
+	for i := 0; i < 4; i++ {
+		sipround(&v0, &v1, &v2, &v3)
+	}
+
+	return v1 ^ v3
+}

lib/halfsiphash/halfsiphash_test.go

@@ -0,0 +1,31 @@
+package halfsiphash
+
+import "testing"
+
+// Test vectors from the reference implementation.
+// Key: 00 01 02 03 04 05 06 07
+// Input: sequence 00, 00 01, 00 01 02, ...
+var vectors32 = []uint32{
+	0x5b9f35a9,
+	0xb85a4727,
+	0x03a662fa,
+	0x04e7fe8a,
+	0x89466e2a,
+	0x69b6fac5,
+	0x23fc6358,
+	0xc563cf8b,
+}
+
+func TestSum32(t *testing.T) {
+	key := [8]byte{0, 1, 2, 3, 4, 5, 6, 7}
+	for i, want := range vectors32 {
+		data := make([]byte, i)
+		for j := range data {
+			data[j] = byte(j)
+		}
+		got := Sum32(data, key)
+		if got != want {
+			t.Errorf("Sum32(len=%d) = %08x, want %08x", i, got, want)
+		}
+	}
+}