[Hacky prototype] Create a shared-memory high-performance reporting service.

services/blamer/public/cpp/blame_classes.h

+// 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.
+
+// Defines all known classes of nodes for attribution, as well as descriptions
+// of their equivalence classes and possible relationships.
+
+#ifndef SERVICES_BLAMER_PUBLIC_CPP_BLAME_CLASSES_H_
+#define SERVICES_BLAMER_PUBLIC_CPP_BLAME_CLASSES_H_
+
+#include "base/hash.h"
+
+namespace blamer {
+
+// An enumeration of all known classes. New ones should strictly be added to
+// the end. Retired classes should be marked as deprecated, and their slots
+// should not be reused. This ensures that IDs are stable across Chrome
+// versions.
+enum class BlameClassId : uint32_t {
+  // This is reserved and used as a sentinel value.
+  UNDEFINED = 0,
+
+  V8_ISOLATE,
+  CONTENT_WEBVIEW,
+  CONTENT_FRAME_TREE_NODE,
+  CONTENT_RENDER_FRAME,
+  BLINK_LOCAL_FRAME,
+  BLINK_REMOTE_FRAME,
+  // New classes should be added here.
+
+  // This should always be last.
+  MAX
+};
+
+// TODO(chrisha): Build "class descriptions", which allow the class to be
+// introspected at runtime. This could include valid parent types, valid child
+// types, valid equivalent class types, etc. This should be present in all
+// process types.
+
+// Templated class for generating IDs given an instance of an object. Each
+// process is expected to have defined one of these for any blame classes that
+// occur in the context of that process. It should satisfy the following
+// interface:
+//
+// // Generate an ID for the given object type. Two equivalent objects in
+// // distinct processes should generate the same ID.
+// static uint32_t GenerateId(const ObjectType& object);
+//
+// By default the implementation of GenerateId will make a call to the following
+// function:
+//
+// static void SerializeObject(const ObjectType& object,
+//                             std::vector<uint8_t>* buffer);
+//
+// Specializations of this class may choose to implement SerializeObject, or
+// to override GenerateId directly.
+template<typename ObjectType>
+class BlameClassIdGenerator {
+ public:
+  // Generate an ID for the given object type. Does so by hashing the results of
+  // SerializeObject().
+  static uint32_t GenerateId(const ObjectType& object) {
+    std::vector<uint8_t> buffer;
+    SerializeObject(object, &buffer);
+    return base::SuperFastHash(buffer.data(), buffer.size());
+  }
+};
+
+}  // namespace blamer
+
+#endif  // SERVICES_BLAMER_PUBLIC_CPP_BLAME_CLASSES_H_