共享指针的简单实现

共享指针的简单实现，主要参考 https://www.cnblogs.com/xiehongfeng100/p/4645555.html

// Study.cpp: 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>
#include <vector>
#include <unordered_map>
#include <unordered_set>
#include <queue>
#include <string>
#include <algorithm>
#include <sstream>
using namespace std;


template<class T>
class SmartPtr
{
public:
	SmartPtr(T *p);
	~SmartPtr();
	SmartPtr(const SmartPtr<T> &orig);                // 浅拷贝
	SmartPtr<T>& operator=(const SmartPtr<T> &rhs);    // 浅拷贝
	void getcount()
	{
		cout << *use_count << " ";
	}
private:
	T * ptr;
	// 将use_count声明成指针是为了方便对其的递增或递减操作
	int *use_count;
};

template<class T>
SmartPtr<T>::SmartPtr(T *p):ptr(p)
{
	use_count = new int(1);
	if (use_count == nullptr)
	{
		p = nullptr;
		cout << " Allocation Error " << endl;
		return;
	}

}

template<class T>
SmartPtr<T>::~SmartPtr()
{
	if (--(*use_count) == 0)
	{
		delete ptr;
		ptr = nullptr;
		delete use_count;
		use_count = nullptr;
	}
}
template<class T>
SmartPtr<T>::SmartPtr(const SmartPtr<T> &orig)
{
	ptr = orig.ptr;
	use_count = orig.use_count;
	++(*use_count);
}
template<class T>
SmartPtr<T>& SmartPtr<T>::operator=(const SmartPtr<T> &rhs)
{
	if (this == &rhs)
		return *this;

	this->~SmartPtr();

	use_count = rhs.use_count;
	++(*use_count);
	ptr = rhs.ptr;

};
int main()
{
	string* p1 = new string("hello");
	SmartPtr<string> sp1(p1);
	string* p2 = new string("hello");
	SmartPtr<string> sp2(p2);
	vector<SmartPtr<string>> vp;
	vp.push_back(sp1);
	vp.push_back(sp2);
	vp.push_back(sp2);
	vp.push_back(sp1);
	cout << "sp1   sp2  :  "; sp1.getcount(); sp2.getcount(); cout << endl;

	vp.pop_back();
	vp.pop_back();
	cout << "sp1   sp2  :  "; sp1.getcount(); sp2.getcount(); cout << endl;


	SmartPtr<string> sp3(sp1);
	cout << "sp1   sp2  :  "; sp1.getcount(); sp2.getcount(); cout << endl;

	sp2 = sp2;

	cout << "sp1   sp2  :  "; sp1.getcount(); sp2.getcount(); cout << endl;

	sp3 = sp2;

	cout << "sp1   sp2  :  "; sp1.getcount(); sp2.getcount(); cout << endl;
	//while (1)
	//{
	//	cin >> a >> b;
	//	cout << ((a & b) + ((a ^ b) >> 1)) << endl;
	//}

	system("pause");
	return 0;
}