Helium: Adding vector clock

blimp/net/helium/vector_clock.cc

Index: blimp/net/helium/vector_clock.cc
diff --git a/blimp/net/helium/vector_clock.cc b/blimp/net/helium/vector_clock.cc
new file mode 100644
index 0000000000000000000000000000000000000000..78bfa4947325a71520fb18286a8600899ea83061
--- /dev/null
+++ b/blimp/net/helium/vector_clock.cc
@@ -0,0 +1,49 @@
+// 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.
+
+#include "blimp/net/helium/vector_clock.h"
+#include <algorithm>

[Kevin M, 2016/09/27 17:31:09]

Add newline before and after <algorithm>

[scf, 2016/09/27 18:29:59]

Done.

+#include "base/logging.h"
+
+namespace blimp {
+
+VectorClock::VectorClock(int32_t local_revision, int32_t remote_revision)
+    : local_revision_(local_revision), remote_revision_(remote_revision) {}
+
+VectorClock::Comparison VectorClock::CompareTo(const VectorClock& other) const {

[Kevin M, 2016/09/27 17:31:09]

Add DCHECK(local_revision_ >= other.local_revision_) at the top.

[scf, 2016/09/27 18:29:58]

Done.

+  if (local_revision_ == other.local_revision_) {
+    if (remote_revision_ == other.remote_revision_) {
+      return VectorClock::Comparison::EqualTo;
+    } else if (remote_revision_ < other.remote_revision_) {
+      return VectorClock::Comparison::LessThan;
+    } else {
+      return VectorClock::Comparison::GreaterThan;
+    }
+  } else {
+    if (local_revision_ > other.local_revision_) {
+      if (remote_revision_ == other.remote_revision_) {
+        return VectorClock::Comparison::GreaterThan;
+      } else {
+        return VectorClock::Comparison::Conflicts;
+      }
+    } else {
+      // its smaller <

[Kevin M, 2016/09/27 17:31:09]

Can you rework comment to be a well formed sentence?

Also:

Maybe consider appending the comment to "else", so you'd have:

} else {  // (local_revision_ == other.local_revision_)

[scf, 2016/09/27 18:29:58]

Done.

+      if (remote_revision_ == other.remote_revision_) {
+        return VectorClock::Comparison::LessThan;
+      } else {
+        return VectorClock::Comparison::Conflicts;
+      }
+    }
+  }
+}
+VectorClock VectorClock::MergeWith(const VectorClock& other) {

[Kevin M, 2016/09/27 17:31:09]

add newline above

[scf, 2016/09/27 18:29:58]

Done.

+  VectorClock result(std::max(local_revision_, other.local_revision_),

[Kevin M, 2016/09/27 17:31:09]

Can you use the getter() to access |other|'s members, here and elsewhere in the
file?

[scf, 2016/09/27 18:29:59]

Done.

+                     std::max(remote_revision_, other.remote_revision_));
+  return result;
+}
+void VectorClock::IncrementLocal() {

[Kevin M, 2016/09/27 17:31:09]

add newline above

[scf, 2016/09/27 18:29:58]

Done.

+  local_revision_++;
+}
+
+}  // namespace blimp