Global Resource Coordinator: Basic service internals

services/resource_coordinator/public/cpp/coordination_unit_id.cc

+// Copyright 2017 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 "services/resource_coordinator/public/cpp/coordination_unit_id.h"
+
+#include "base/logging.h"
+#include "base/numerics/safe_conversions.h"
+#include "third_party/smhasher/src/MurmurHash2.h"

[nasko, 2017/04/21 00:17:32]

Doesn't std::hash suffice here?

[oystein (OOO til 10th of July), 2017/04/21 17:57:55]

I had that originally as well, primiano in #2 suggested the change as std::hash
has a high chance of collisions when string prefixes of the hashed strings
remain unchanged (which could often be the case here):
https://groups.google.com/a/chromium.org/forum/#!msg/chromium-dev/-rXNiOoIU4A...

[nasko, 2017/04/24 22:10:50]

Acknowledged.

+
+namespace resource_coordinator {
+
+// The seed to use when taking the murmur2 hash of the id.
+const uint64_t kMurmur2HashSeed = 0;
+
+CoordinationUnitID::CoordinationUnitID()
+    : id(0), type(CoordinationUnitType::INVALID_TYPE) {}
+
+CoordinationUnitID::CoordinationUnitID(const CoordinationUnitType& type,
+                                       const std::string& new_id)

[nasko, 2017/04/21 00:17:32]

Let's keep the parameter names in sync between header and implementation. It is
listed as "id" in the header.

[oystein (OOO til 10th of July), 2017/04/21 17:57:55]

Done.

+    : type(type) {
+  DCHECK(base::IsValueInRangeForNumericType<int>(new_id.size()));
+  id = MurmurHash2(&new_id.front(), static_cast<int>(new_id.size()),
+                   kMurmur2HashSeed);
+}
+
+}  // resource_coordinator