ros_node_base.hpp

// Copyright 2024 Robin Müller
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#pragma once
 
#include <functional>
#include <memory>
#include <mutex>
#include <string>
#include <unordered_map>
 
#include "auto_apms_behavior_tree_core/node/ros_node_context.hpp"
#include "behaviortree_cpp/tree_node.h"
#include "rclcpp/logger.hpp"
 
namespace auto_apms_behavior_tree::core
{

class RosNodeBase
{
public:
  using Config = BT::NodeConfig;
  using Context = RosNodeContext;
 
protected:
  RosNodeBase(const std::string & instance_name, Context context);
 
  ~RosNodeBase() = default;

  void applyPortAliasing(const BT::TreeNode * node) const;

  template <typename InstanceT>
  std::shared_ptr<InstanceT> getSharedEntity(
    const std::string & entity_name, const std::function<std::shared_ptr<InstanceT>()> & factory);
 
  const Context context_;
  const rclcpp::Logger logger_;
};
 
template <typename InstanceT>
std::shared_ptr<InstanceT> RosNodeBase::getSharedEntity(
  const std::string & entity_name, const std::function<std::shared_ptr<InstanceT>()> & factory)
{
  // A separate registry (and guarding mutex) is instantiated for each InstanceT. Being function-local statics of a
  // template, they have vague linkage and are therefore merged into a single instance process-wide across all
  // translation units.
  static std::mutex mutex;
  static std::unordered_map<std::string, std::weak_ptr<InstanceT>> registry;
 
  // Key by the owning ROS 2 node so that entities belonging to different nodes never collide.
  const std::string key = context_.getFullyQualifiedRosNodeName() + "/" + entity_name;
 
  std::unique_lock lock(mutex);
  if (const auto it = registry.find(key); it != registry.end()) {
    if (const std::shared_ptr<InstanceT> existing = it->second.lock()) return existing;
  }
  const std::shared_ptr<InstanceT> instance = factory();
  registry[key] = instance;
  return instance;
}
 
}  // namespace auto_apms_behavior_tree::core