Helium: Initial proto and Syncable interface definition

blimp/net/helium/vector_clock_generator.h

Index: blimp/net/helium/vector_clock_generator.h
diff --git a/blimp/net/helium/vector_clock_generator.h b/blimp/net/helium/vector_clock_generator.h
new file mode 100644
index 0000000000000000000000000000000000000000..a5f97ac59493cb2c6dcf1a41d19919f957fc95bc
--- /dev/null
+++ b/blimp/net/helium/vector_clock_generator.h
@@ -0,0 +1,37 @@
+// 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. These generators are going to be used one per host

[Kevin M, 2016/10/05 23:41:30]

"These generators" - there's only one of them?

[scf, 2016/10/06 19:47:17]

Done.

+// (client or engine) to ensure they have a single clock domain.
+//
+// This greatly simplify things as VectorClocks will be behaving similar to time

[Kevin M, 2016/10/05 23:41:30]

Paragraph seems like a design doc detail.

[scf, 2016/10/06 19:47:17]

removed

+// concept. VectorClocks of different objects in the same host can be compared
+// directly and well as VectorClocks between different objects in different
+// hosts (As long as you invert local and remote pairs).
+class VectorClockGenerator {
+ public:
+  VectorClockGenerator() {}
+
+  void increment() { clock_.IncrementLocal(); }

[Kevin M, 2016/10/05 23:41:30]

capital I Increment()

+
+  const VectorClock& current() { return clock_; }
+
+ private:
+  VectorClock clock_;
+
+  DISALLOW_COPY_AND_ASSIGN(VectorClockGenerator);
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_HELIUM_VECTOR_CLOCK_GENERATOR_H_