newValue/3part/lp_qt_utils/inc/lp_singleton_base.h

#pragma once

#include <mutex>
#include <atomic>

template<class T>
class lp_singleton_base
{
public:
	static T* instance()
	{
		T *sin = s_this.load(std::memory_order_acquire);

		if (!sin) {
			std::lock_guard<std::mutex> locker(s_mutex);
			sin = s_this.load(std::memory_order_relaxed);
			if (!sin) {
				sin = new T;
				s_this.store(sin, std::memory_order_release);
			}
		}

		return sin;
	}

	static void uninstance()
	{
		T *sin = s_this.load(std::memory_order_relaxed);
		if (sin) {
			std::lock_guard<std::mutex> locker(s_mutex);
			delete sin;
			sin = nullptr;
		}
	}

protected:
	lp_singleton_base() = default;
	virtual ~lp_singleton_base() = default;
private:
	lp_singleton_base(const T&) = delete;
	T& operator=(const T&) = delete;

	static std::atomic<T*> s_this;
	static std::mutex s_mutex;
};

template<class T>
std::atomic<T*> lp_singleton_base<T>::s_this;

template<class T>
std::mutex lp_singleton_base<T>::s_mutex;