template <class T>
class SharedPtr
{
public:
    SharedPtr(T* ptr = nullptr)
        : _ptr(ptr)
        , _pRefCount(new int(1))
        , _pMutex(new mutex)
    {}

    ~SharedPtr()
    {
        Release();
    }

    SharedPtr(const SharedPtr<T>& sp)
        : _ptr(sp._ptr)
        , _pRefCount(sp._pRefCount)
        , _pMutex(sp._pMutex)
    {
        AddRefCount();
    }

    
 
// 賦值
    SharedPtr<T>& operator=(const SharedPtr<T>& sp)
    {
        if (_ptr != sp._ptr)
        {
            // 釋放管理的舊資源
            Release();
            // 共享管理新物件的資源，並增加引用計數
            _ptr = sp._ptr;
            _pRefCount = sp._pRefCount;
            _pMutex = sp._pMutex;
            AddRefCount();
        }
        
 
return *this;
    }


    T& operator*()
    {
        return *_ptr;
    }

    T* operator->()
    {
        return _ptr;
    }

    int UseCount()
    {
        return *_pRefCount;
    }

    T* Get()
    {
        return _ptr;
    }

    void AddRefCount()
    {
        // 加鎖或者使用加1的原子操作
        _pMutex->lock
 
();
        ++(*_pRefCount);
        _pMutex->unlock();
    }

private:
    void Release()
    {
        bool deleteflag = false;
        // 引用計數減1，如果減到0，則釋放資源
        _pMutex->lock();
        if (--(*_pRefCount) == 0)
        {
            delete _ptr;
            delete _pRefCount;
            deleteflag = true;
        }
        _pMutex->unlock();

        if (deleteflag == true)
            delete _pMutex;
    }
private:
    int* _pRefCount; // 引用計數
    T* _ptr; // 指向管理資源的指標
    mutex* _pMutex; // 互斥鎖
};

參考：https://blog.csdn.net/qq_56663697/article/details/123964427