Merge pull request briansmith#4 from xnum/master

Fix generateMultiHash write data to source data slice

hash.go

@@ -139,7 +139,10 @@ func bytesToUint64(b []byte) uint64 {
 // generateMultihash returns 4 64-bit (2 x 128-bit) MurmurHash3 hashes.
 func generateMultiHash(data []byte) [4]uint64 {
 	h1, h2 := murmur128(data)
-	h3, h4 := murmur128(append(data, single))
+	buff := make([]byte, len(data)+1)
+	copy(buff, data)
+	buff[len(data)] = single
+	h3, h4 := murmur128(buff)
 	return [4]uint64{h1, h2, h3, h4}
 }
 

hash_test.go

@@ -0,0 +1,37 @@
+package ring
+
+import "testing"
+
+func BenchmarkGenerateMultiHash(b *testing.B) {
+	data := []byte{0x00, 0x12, 0x34, 0x56, 0x78, 0x00}
+	buff := make([]byte, len(data))
+	for i := 0; i < b.N; i++ {
+		copy(buff, data)
+		generateMultiHash(buff[1:5])
+	}
+}
+
+func TestGenerateMultiHash(t *testing.T) {
+	data := []byte{
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+		0x00, 0x12, 0x34, 0x56, 0x78, 0x00,
+	}
+	buff := make([]byte, len(data))
+	copy(buff, data)
+	generateMultiHash(buff[1:20])
+
+	for i := range data {
+		if data[i] != buff[i] {
+			t.Fatalf("data not match at index: %v", i)
+		}
+	}
+}