util: added reference tracker

RT, reference tracker, is key-based implementation of a reference counter.
Unlike an integer-based counter, RT counts references by tracking unique
keys. This allows accounting in situations where idempotency must be
preserved. It guarantees there will be no duplicit increments or decrements
of the counter.

Signed-off-by: Robert Vasek <robert.vasek@cern.ch>

internal/util/reftracker/v1/refcount_test.go

@@ -0,0 +1,51 @@
+/*
+Copyright 2022 The Ceph-CSI Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package v1
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestV1RefCountBytes(t *testing.T) {
+	t.Parallel()
+
+	var (
+		refCountBytes          = []byte{0x0, 0x0, 0x0, 0x7B}
+		refCountValue          = refCount(123)
+		wrongSizeRefCountBytes = []byte{0, 0, 1}
+	)
+
+	t.Run("ToBytes", func(ts *testing.T) {
+		ts.Parallel()
+
+		bs := refCountValue.toBytes()
+		assert.Equal(ts, refCountBytes, bs)
+	})
+
+	t.Run("FromBytes", func(ts *testing.T) {
+		ts.Parallel()
+
+		rc, err := refCountFromBytes(refCountBytes)
+		assert.NoError(ts, err)
+		assert.Equal(ts, refCountValue, rc)
+
+		_, err = refCountFromBytes(wrongSizeRefCountBytes)
+		assert.Error(ts, err)
+	})
+}