whellvalue/src/tpMain/lp_singleton.h

#ifndef LP_SINGLETON_H
#define LP_SINGLETON_H

#include <mutex>
#include <atomic>

template<class T>
class lp_singleton
{
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() = default;
    virtual ~lp_singleton() = default;
private:
    lp_singleton(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<T>::s_this;

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

#endif // LP_SINGLETON_H