C++ shared_ptr的实现

在前面放一个源码剖析中看到的auto_ptr的定义文件，补充一点构造函数必须要为explicit，避免一些隐式转换。

 补充一点：reset（rhs）函数会删除auto_ptr指向的对象，然后用rhs指向的新建一个

 auto_ptr release函数意在将调⽤该函数的智能指针的所有权转移，如 ptr = my_auto2.release ();就是将my_auto2的 所有权转给ptr。

 

比较完整的复现了STL中的shared_ptr中的功能，可以加载删除器，并且加入了互斥，可以在多线程中使用。

#include <iostream>
#include <mutex>
using namespace std;

template <typename T>
class Shared_ptr {
public:
	Shared_ptr(T * t_ptrToObject) {
		m = new mutex();
		this->haveDeleterOrNot = t_ptrToObject;
		this->count = malloc(sizeof(int));
		(*this->count) = 1;
		this->haveDeleterOrNot = false;
	}
	
	Shared_ptr(T * t_ptrToObject, void (*t_deleter)(T *)) {
		this->m = new mutex();
		this->ptrToObject = t_ptrToObject;
		
		this->count = (int *)malloc(sizeof(int));
		(*this->count) = 1;
		
		this->deleter = t_deleter;
		this->haveDeleterOrNot = true;
	}
	
	Shared_ptr(const Shared_ptr & rhs) {
		this->m = rhs.m;
		(*m).lock();
		this->ptrToObject = rhs.ptrToObject;
		this->count = rhs.count;
		
		(*(rhs.count)) = (*(rhs.count)) + 1;
		
		this->haveDeleterOrNot = rhs.haveDeleterOrNot;
		this->deleter = rhs.deleter; 
		
		(*m).unlock();
	}
	
	
	Shared_ptr & operator= (const Shared_ptr & rhs) {
		this->m = rhs.m;
		(*m).lock();
		this->ptrToObject = rhs.ptrToObject;
		this->count = rhs.count;
		
		(*(rhs.count)) = (*(rhs.count)) + 1;
		
		this->haveDeleterOrNot = rhs.haveDeleterOrNot;
		this->deleter = rhs.deleter; 
		
		(*m).unlock();
		
		return (*this);
	}
	
	
	//rewrite the operator 
	T & operator* () {
		return *(this->ptrToObject);
	}
	
	T * operator-> () {
		return this->ptrToObject;
	}
	
	
	~Shared_ptr() {
		(*m).lock();
		(*count) = (*count) - 1;
		
		if ((*count) == 0 && this->haveDeleterOrNot) {
			(*(this->deleter))(this->ptrToObject);	
		}
		else if ((*count) == 0 && !this->haveDeleterOrNot) {
			delete this->ptrToObject;
		}
		
		(*m).unlock();
	}
	
	int getCount() const{
		return *this->count;
	}
	
private:
	T * ptrToObject;
	int * count;
	bool haveDeleterOrNot; 
	void (*deleter)(T *);	
	mutex * m;
};

void test(int * num) {
	cout << "num: " << *num << endl;
}


int main() {
	int * num = new int(5); 
	Shared_ptr<int> sp1(num, test);
	Shared_ptr<int> sp2(sp1);
	Shared_ptr<int> sp3 = sp1;
	
	cout << sp1.getCount()  << endl;
//	void (*deleter)(int *);
//	deleter = test;
//	void (*t_deleter)(int *);
//	t_deleter = deleter;
//	(*t_deleter)(num);
	return 0;
}