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

services/blamer/public/cpp/blame_node.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.
+
+#ifndef SERVICES_BLAMER_PUBLIC_CPP_BLAME_NODE_H_
+#define SERVICES_BLAMER_PUBLIC_CPP_BLAME_NODE_H_
+
+#include "base/memory/ref_counted.h"
+
+#include <vector>
+
+#include "services/blamer/public/cpp/blame_classes.h"
+
+namespace blamer {
+
+struct FlatBlameNode;
+
+// A node is a logical unit to which we want to attribute resource consumption
+// (CPU, network, memory usage, power, disk, etc). An example of a node is an
+// <iframe> element on a web page, or a "tab" on in a browser window. The
+// collection of all nodes implicitly creates a DAG (nodes may have multiple
+// parents) with a single implicit common root (the browser).
+//
+// A BlameNode should be constructed, attached to parents, attached to
+// equivalence classes, etc, and then finalized. Once it has been finalized it
+// will be committed to the shared memory buffer, visible by other processes and
+// able to be used to start collecting metrics.
+class BlameNode : public base::RefCounted<BlameNode> {
+ public:
+  // Constructs a blame node with the given class ID and object ID.
+  BlameNode(BlameClassId class_id, uint32_t object_id);
+
+  // Adds a parent to this BlameNode. This can be called repeatedly. Can only
+  // be called prior to committing this node.
+  void AddParent(scoped_refptr<BlameNode> parent);
+
+  // Adds an equivalence class to this BlameNode. Can only be called prior to
+  // committing this node.
+  void AddEquivalence(BlameClassId class_id, uint32_t equivalence_key);
+
+  // Commits this node.
+  void Commit();
+
+  FlatBlameNode* flat_blame_node() const { return flat_blame_node_; }
+  //FlatBlameData* flat_blame_data() const { return flat_blame_data_; }
+
+ private:
+  friend class base::RefCounted<BlameNode>;
+  using Equivalence = std::pair<BlameClassId, uint32_t>;
+
+  ~BlameNode();
+
+  std::vector<scoped_refptr<BlameNode>> parents_;
+  std::vector<Equivalence> equivalences_;
+
+  // Pointer to the exported blame node description for this node. This is
+  // initially null and only populated when committed.
+  FlatBlameNode* flat_blame_node_;
+
+  // Pointer to the exported blame data associated with this node. This is
+  // initially null and only populated when committed.
+  //FlatBlameData* flat_blame_data_;
+};
+
+// This acts as a lightweight reference to another blame node.
+struct FlatBlameNodeReference {
+  // The class ID to which the node belongs. Actually a BlameClassId.
+  uint32_t blame_class_id;
+  // The ID of the node. This is namespaced by |blame_class_id|.
+  uint32_t object_id;
+};
+
+// This describes an equivalence for a blame node.
+struct FlatBlameNodeEquivalence {
+  // The class ID to which the node belongs. Actually a BlameClassId.
+  uint32_t blame_class_id;
+  // The common key used by the remote object instance in order to tie the
+  // objects together. This is user defined.
+  uint32_t equivalence_key;
+};
+
+// This is a flat POD description of a blame node.
+struct FlatBlameNode {
+  // The class ID to which this node belongs. Actually a BlameClassId.
+  uint32_t blame_class_id;
+
+  // The proess-stable ID of the object this node represents. This is namespaced
+  // by |blame_class_id|.
+  uint32_t object_id;
+
+  // The number of parents this node has.
+  uint16_t parent_count;
+
+  // The number of equivalences this node has.
+  uint16_t equivalence_count;
+
+  // TODO
+};
+
+}  // namespace blamer
+
+#endif  // SERVICES_BLAMER_PUBLIC_CPP_BLAME_NODE_H_