chromium/components/performance_manager/public/graph/node_attached_data.h

// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_PERFORMANCE_MANAGER_PUBLIC_GRAPH_NODE_ATTACHED_DATA_H_
#define COMPONENTS_PERFORMANCE_MANAGER_PUBLIC_GRAPH_NODE_ATTACHED_DATA_H_

#include <memory>

#include "base/check_op.h"

namespace performance_manager {

class Node;

// NodeAttachedData allows external observers of the graph to store data that is
// associated with a graph node, providing lifetime management as a service.
//
// External (to performance_manager) implementations of NodeAttachedData should
// derive from ExternalNodeAttachedDataImpl. For internal implementations refer
// to NodeAttachedDataImpl and see node_attached_data_impl.h.
class NodeAttachedData { … };

// Implements NodeAttachedData for a given UserDataType.
//
// In order for a UserDataType to be attached to a node of type |NodeType| it
// must have a constructor of the form "UserDataType(const NodeType* node)".
template <typename UserDataType>
class ExternalNodeAttachedDataImpl : public NodeAttachedData { … };

// Everything below this point is pure implementation detail.

// Provides access for setting/getting data in the map based storage. Not
// intended to be used directly, but rather by (External)NodeAttachedDataImpl.
class NodeAttachedDataMapHelper { … };

// Implementation of ExternalNodeAttachedDataImpl, which is declared in the
// corresponding public header. This helps keep the public headers as clean as
// possible.

// static
template <typename UserDataType>
constexpr int ExternalNodeAttachedDataImpl<UserDataType>::kUserDataKey;

template <typename UserDataType>
template <typename NodeType>
UserDataType* ExternalNodeAttachedDataImpl<UserDataType>::GetOrCreate(
    const NodeType* node) { … }

template <typename UserDataType>
template <typename NodeType>
UserDataType* ExternalNodeAttachedDataImpl<UserDataType>::Get(
    const NodeType* node) { … }

template <typename UserDataType>
template <typename NodeType>
bool ExternalNodeAttachedDataImpl<UserDataType>::Destroy(const NodeType* node) { … }

}  // namespace performance_manager

#endif  // COMPONENTS_PERFORMANCE_MANAGER_PUBLIC_GRAPH_NODE_ATTACHED_DATA_H_