手写智能指针

template<typename T>
class shared_ptr_my
{
public:
    shared_ptr_my(T* p=nullptr);

    shared_ptr_my(shared_ptr_my&);
    shared_ptr_my& operator=(shared_ptr_my&);

    shared_ptr_my(shared_ptr_my&&) noexcept;
    shared_ptr_my& operator=(shared_ptr_my&&);

    T* operator->();
    T& operator*();
    bool unique();
    std::size_t use_count();
    ~shared_ptr_my();

private:
    int* count;
    T* p;
};

template<typename T> 
shared_ptr_my<T>::shared_ptr_my(T* p):count(new int(1)),p(p)
{
    cout << "构造函数 "  << endl;
}

template<typename T>
shared_ptr_my<T>::~shared_ptr_my() 
{
    if (-- * count == 0) {
        delete count;
        delete p;
    }
}
template<typename T>
shared_ptr_my<T>::shared_ptr_my(shared_ptr_my& other):p(other.p),count(&(++*other.count))
{
    cout << "拷贝构造" << endl;
}
template<typename T>
T* shared_ptr_my<T>::operator->() {
    return p;
}
template<typename T>
T& shared_ptr_my<T>::operator*() {
    return *p;
}
template<typename T>
shared_ptr_my<T>& shared_ptr_my<T>::operator=(shared_ptr_my& other) {
    ++* other.count;
    if (-- * count == 0) {
        delete count;
        delete p;
    }
    this->p = other.p;
    this->count = other.count;
    cout << "拷贝赋值  "<< endl;
    return *this;
}

template<typename T>
shared_ptr_my<T>::shared_ptr_my(shared_ptr_my&& other)noexcept :p(std::move(other.p)),count(std::move(other.count)){
    other.count = nullptr;
    cout << "移动构造 " << endl;
}
template<typename T>
shared_ptr_my<T>& shared_ptr_my<T>::operator=(shared_ptr_my&& other) {
    if (this == &other) {//防止自我赋值 判断this与other的地址
        return *this;
    }
    p = other.p;
    other.p = nullptr;
    count = other.count;
    other.count = nullptr;
    cout << "移动赋值  " << endl;
    return *this;
}
template<typename T>
std::size_t shared_ptr_my<T>::use_count() {
    return *count;
}
template<typename T>
bool shared_ptr_my<T>::unique() {
    return *count == 1;
}

int main()
{
    
    shared_ptr_my<string> first(new string("first"));//构造
    cout << first.use_count() << endl;
    first = first;
    cout << first.use_count() << endl;
    first = std::move(first);
    cout << first.use_count() << endl;
    shared_ptr_my<string> second(first);//拷贝构造
    cout << second.use_count() << endl;
    shared_ptr_my<string> three(new string("three"));
    cout << three.use_count() << endl;
    three = second;//拷贝赋值
    cout << three.use_count() << endl;
    shared_ptr_my<string> four(std::move(three));//移动构造
    cout << four.use_count() << endl;
    shared_ptr_my<string> five(new string("five"));
    cout << five.use_count() << endl;
    five = std::move(four);//移动赋值
    cout << five.use_count() << endl;
}