//前置声明 因为在使用sharedptr时可能会产生循环引用的缺陷，所以使用weakedptr进行辅助
template <class T>
class WeakedPtr;
template<class T>
class MySharedPtr
{
public:
//定义为友元类
friend class WeakedPtr<T>;
MySharedPtr(T* ptr = NULL) :_ptr(ptr), _refCount(new int(1))
{}
~MySharedPtr()
{
if (--(*_refCount) == 0)
{
delete _ptr;
delete _refCount;
}
}
//s1(s2)
MySharedPtr(const MySharedPtr<T>& sp) :_ptr(sp._ptr), _refCount(sp._refCount)
{
(*_refCount)++;
}
//sp1 = sp2
MySharedPtr<T>& operator=(MySharedPtr<T>& sp)
{
if (_ptr != sp._ptr)
{
if (--(*_refCount) == 0)
{
delete _ptr;
delete _refCount;
}
_ptr = sp._ptr;
_refCount = sp._refCount;
(*_refCount)++;
}
return *this;
}
//为了像指针一样才进行*\->的重载
//->的重载
T* operator->()
{
return _ptr;
}
//*的重载
T& operator*()
{
return *_ptr;
}
//查看引用计数的多少
int UseCount()
{
return *_refCount;
}
private:
T* _ptr;
int* _refCount;//一块空间有一个指针
};
template <class T>
class WeakedPtr
{
public:
WeakedPtr() :_ptr(NULL)
{}
WeakedPtr(const MySharedPtr<T>& sp)
:_ptr(sp._ptr)
{}
WeakedPtr<T>& operator=(const MySharedPtr<T>&sp)
{
_ptr = sp._ptr;
return *this;
}
T& operator* ()
{
return *_ptr;
}
T* operator->()
{
return _ptr;
}
private:
T* _ptr;
};
struct ListNode
{
int _data;
WeakedPtr<ListNode> _next;
WeakedPtr<ListNode> _prev;
~ListNode()
{
cout << "~ListNode" << endl;
}
};
void testMySharedPtr()
{
//SharePtr<int> sp1(new int(1));
//SharePtr<int> sp2(sp1);
MySharedPtr<ListNode> cur(new ListNode);
MySharedPtr<ListNode> next(new ListNode);
cout << cur.UseCount() << endl;
cout << next.UseCount() << endl;
cur->_next = next;
next->_prev = cur;
cout << cur.UseCount() << endl;
cout << next.UseCount() << endl;
}
