Helium: Initial proto and Syncable interface definition

blimp/net/helium/vector_clock_generator.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BLIMP_NET_HELIUM_VECTOR_CLOCK_GENERATOR_H_
+#define BLIMP_NET_HELIUM_VECTOR_CLOCK_GENERATOR_H_
+
+#include "base/macros.h"
+#include "blimp/net/helium/vector_clock.h"
+
+namespace blimp {
+
+// This entity is responsible for generating monotonically increasing values
+// of VectorClocks. This generator is going to be used one per host
+// (client or engine) to ensure they have a single clock domain.
+//
+class VectorClockGenerator {
+ public:
+  VectorClockGenerator() {}
+
+  void Increment() { clock_.IncrementLocal(); }
+
+  const VectorClock& current() { return clock_; }
+
+ private:
+  VectorClock clock_;
+
+  DISALLOW_COPY_AND_ASSIGN(VectorClockGenerator);
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_HELIUM_VECTOR_CLOCK_GENERATOR_H_