C++ 智能指针简单实现

template <typename T>
class SharedPtr {
  private:
    size_t* m_count_;
    T* m_ptr_;

  public:
    //构造函数
    SharedPtr() : m_ptr_(nullptr), m_count_(new size_t) {}
    SharedPtr(T* ptr) : m_ptr_(ptr), m_count_(new size_t) { m_count_ = 1; }
    //析构函数
    ~SharedPtr() {
        --(*m_count_);
        if (*m_count_ == 0) {
            delete m_ptr_;
            delete m_count_;
            m_ptr_ = nullptr;
            m_count_ = nullptr;
        }
    }
    //拷贝构造函数
    SharedPtr(const SharedPtr& ptr) {
        m_count_ = ptr.m_count_;
        m_ptr_ = ptr.m_ptr_;
        ++(*m_count_);
    }
    //拷贝赋值运算
    void operator=(const SharedPtr& ptr) { SharedPtr(std::move(ptr)); }
    //移动构造函数
    SharedPtr(SharedPtr&& ptr) : m_ptr_(ptr.m_ptr_), m_count_(ptr.m_count_) { ++(*m_count_); }
    //移动赋值运算
    void operator=(SharedPtr&& ptr) { SharedPtr(std::move(ptr)); }
    //解引用
    T& operator*() { return *m_ptr_; }
    //箭头运算
    T* operator->() { return m_ptr_; }
    //᯿载bool操作符
    operator bool() { return m_ptr_ == nullptr; }
    T* get() { return m_ptr_; }
    size_t use_count() { return *m_count_; }
    bool unique() { return *m_count_ == 1; }
    void swap(SharedPtr& ptr) { std::swap(*this, ptr); }
};

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