Copy all byte slices from decoder

While trying to optimize things I overread this: "the byte slices returned by the Decoder methods are only valid until the next call to any other Decode method."

lineprotocol_test.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+	"log"
+	"testing"
+
+	"github.com/influxdata/line-protocol/v2/lineprotocol"
+)
+
+const TestDataClassicFormat string = `
+m1,cluster=ctest,hostname=htest1,type=node value=1 123456789
+m2,cluster=ctest,hostname=htest1,type=node value=2 123456789
+m3,cluster=ctest,hostname=htest2,type=node value=3 123456789
+m4,cluster=ctest,hostname=htest2,type=core,type-id=1 value=4 123456789
+m4,cluster=ctest,hostname=htest2,type-id=2,type=core value=5 123456789
+`
+
+func TestLineprotocolDecoder(t *testing.T) {
+	prevMemoryStore := memoryStore
+	t.Cleanup(func() {
+		memoryStore = prevMemoryStore
+	})
+
+	memoryStore = NewMemoryStore(map[string]MetricConfig{
+		"m1": {Frequency: 1},
+		"m2": {Frequency: 1},
+		"m3": {Frequency: 1},
+		"m4": {Frequency: 1},
+	})
+
+	dec := lineprotocol.NewDecoderWithBytes([]byte(TestDataClassicFormat))
+	if err := decodeLine(dec); err != nil {
+		log.Fatal(err)
+	}
+
+	// memoryStore.DebugDump(bufio.NewWriter(os.Stderr))
+
+	h1 := memoryStore.GetLevel([]string{"ctest", "htest1"})
+	h1b1 := h1.metrics[memoryStore.metrics["m1"].offset]
+	h1b2 := h1.metrics[memoryStore.metrics["m2"].offset]
+	if h1b1.data[0] != 1.0 || h1b2.data[0] != 2.0 {
+		log.Fatal()
+	}
+
+	h2 := memoryStore.GetLevel([]string{"ctest", "htest2"})
+	h2b3 := h2.metrics[memoryStore.metrics["m3"].offset]
+	if h2b3.data[0] != 3.0 {
+		log.Fatal()
+	}
+
+	h2c1 := memoryStore.GetLevel([]string{"ctest", "htest2", "core1"})
+	h2c1b4 := h2c1.metrics[memoryStore.metrics["m4"].offset]
+	h2c2 := memoryStore.GetLevel([]string{"ctest", "htest2", "core2"})
+	h2c2b4 := h2c2.metrics[memoryStore.metrics["m4"].offset]
+	if h2c1b4.data[0] != 4.0 || h2c2b4.data[0] != 5.0 {
+		log.Fatal()
+	}
+}