GpgFunctionObject.h

 
#ifndef GPGFRONTEND_ZH_CN_TS_FUNCTIONOBJECT_H
#define GPGFRONTEND_ZH_CN_TS_FUNCTIONOBJECT_H
 
#include <map>
#include <memory>
#include <mutex>
#include <shared_mutex>
#include <stdexcept>
#include <string>
 
#include "GpgConstants.h"
 
namespace GpgFrontend {
 
template <typename T>
class SingletonFunctionObject {
 public:
  static T& GetInstance(
      int channel = GpgFrontend::GPGFRONTEND_DEFAULT_CHANNEL) {
    static_assert(std::is_base_of<SingletonFunctionObject<T>, T>::value,
                  "T not derived from SingletonFunctionObject<T>");
 
    auto _p_pbj = find_object_in_channel(channel);
    if (_p_pbj == nullptr)
      return *set_object_in_channel(channel, std::make_unique<T>(channel));
    else
      return *_p_pbj;
  }
 
  static T& CreateInstance(int channel,
                           std::function<std::unique_ptr<T>(void)> factory) {
    static_assert(std::is_base_of<SingletonFunctionObject<T>, T>::value,
                  "T not derived from SingletonFunctionObject<T>");
 
    auto _p_pbj = find_object_in_channel(channel);
    if (_p_pbj == nullptr)
      return *set_object_in_channel(channel, std::move(factory()));
    else
      return *_p_pbj;
  }
 
  static T& CreateInstance(int channel, std::unique_ptr<T> p_obj = nullptr) {
    static_assert(std::is_base_of<SingletonFunctionObject<T>, T>::value,
                  "T not derived from SingletonFunctionObject<T>");
 
    auto _p_pbj = find_object_in_channel(channel);
    if (_p_pbj == nullptr)
      return *set_object_in_channel(channel, std::move(p_obj));
    else
      return *_p_pbj;
  }
 
  static T& ReleaseChannel(int channel) {
    decltype(_instances_map.end()) _it;
    {
      std::shared_lock lock(_instances_mutex);
      _it = _instances_map.find(channel);
    }
    if (_it != _instances_map.end()) _instances_map.erase(_it);
    DLOG(INFO) << "channel" << channel << "released";
  }
 
  static int GetDefaultChannel() { return _default_channel; }
 
  [[nodiscard]] int GetChannel() const { return channel_; }
 
  SingletonFunctionObject(T&&) = delete;
 
  SingletonFunctionObject(const T&) = delete;
 
  void operator=(const T&) = delete;
 
 protected:
  SingletonFunctionObject() = default;
 
  explicit SingletonFunctionObject(int channel) : channel_(channel) {}
 
  virtual ~SingletonFunctionObject() = default;
 
  void SetChannel(int channel) { this->channel_ = channel; }
 
 private:
  int channel_ = _default_channel;                          
  static int _default_channel;                              
  static std::mutex _instance_mutex;                        
  static std::shared_mutex _instances_mutex;                
  static std::unique_ptr<T> _instance;                      
  static std::map<int, std::unique_ptr<T>> _instances_map;  
 
  static T* find_object_in_channel(int channel) {
    // read _instances_map
    decltype(_instances_map.end()) _it;
    {
      std::shared_lock lock(_instances_mutex);
      _it = _instances_map.find(channel);
      if (_it == _instances_map.end())
        return nullptr;
      else
        return _it->second.get();
    }
  }
 
  static T* set_object_in_channel(int channel, std::unique_ptr<T> p_obj) {
    {
      if (p_obj == nullptr) p_obj = std::make_unique<T>();
      T* obj = p_obj.get();
      obj->SetChannel(channel);
      {
        std::unique_lock lock(_instances_mutex);
        _instances_map.insert({channel, std::move(p_obj)});
      }
      return obj;
    }
  }
};
 
template <typename T>
int SingletonFunctionObject<T>::_default_channel =
    GpgFrontend::GPGFRONTEND_DEFAULT_CHANNEL;
 
template <typename T>
std::mutex SingletonFunctionObject<T>::_instance_mutex;
 
template <typename T>
std::shared_mutex SingletonFunctionObject<T>::_instances_mutex;
 
template <typename T>
std::unique_ptr<T> SingletonFunctionObject<T>::_instance = nullptr;
 
template <typename T>
std::map<int, std::unique_ptr<T>> SingletonFunctionObject<T>::_instances_map;
 
}  // namespace GpgFrontend
 
#endif  // GPGFRONTEND_ZH_CN_TS_FUNCTIONOBJECT_H