Helium: Initial proto and Syncable interface definition

blimp/net/helium/vector_clock.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_H_
 #define BLIMP_NET_HELIUM_VECTOR_CLOCK_H_
 
 #include <stdint.h>
 
+#include "blimp/common/proto/helium.pb.h"
+
 namespace blimp {
 
 // From wikipedia:
 // A vector clock is an algorithm for generating a partial ordering of events
 // in a distributed system and detecting causality violations. This is used
 // in Blimp to allow client and server modify a local copy of an object and
 // later be able to detect ordering or conflicts if any.
 //
 // For more info see:
 // https://en.wikipedia.org/wiki/Vector_clock
 
 typedef uint32_t Revision;
 
 class VectorClock {

[Sriram, 2016/09/29 18:52:21]

Add comment on threading expectation of the object.

  public:
   enum class Comparison { LessThan, EqualTo, GreaterThan, Conflict };
 
   VectorClock(Revision local_revision, Revision remote_revision);
   VectorClock();
 
   // Compares two vector clocks. There are 4 possibilities for the result:
   // * LessThan: One revision is equal and for the other is smaller.
   // (1,0).CompareTo((2, 0));
   // * EqualTo: Both revisions are the same.
@@ skipping 15 matching lines @@
   void set_local_revision(Revision local_revision) {
     local_revision_ = local_revision;
   }
 
   Revision remote_revision() const { return remote_revision_; }
 
   void set_remote_revision(Revision remote_revision) {
     remote_revision_ = remote_revision;
   }
 
+  // Create the ProtoBuf object corresponding to this object
+  helium::VectorClock CreateProto();
+
+  // Inverts the local and remote components respectively
+  VectorClock Invert();

[Sriram, 2016/09/29 18:52:21]

Can you update the comment to tell when it would be used?

[scf, 2016/09/29 23:13:39]

Done.

+
  private:
   Revision local_revision_ = 0;
   Revision remote_revision_ = 0;
 };
 
 }  // namespace blimp
 
 #endif  // BLIMP_NET_HELIUM_VECTOR_CLOCK_H_