my_shared_ptr.h
#include <iostream>
#include <atomic>
template<typename T>
class my_shared_ptr {
private:
T* m_ptr = nullptr;
unsigned int* ref_count = nullptr;
void swap(my_shared_ptr&);
public:
my_shared_ptr() :m_ptr(nullptr), ref_count(nullptr) {};
my_shared_ptr(T* ptr) :m_ptr(ptr), ref_count(new unsigned int(1)) {};
~my_shared_ptr()
{
if (ref_count == nullptr)
{
return;
}
(*ref_count)--;
if (*ref_count > 0)
{
return;
}
if (m_ptr != nullptr)
{
m_ptr = nullptr;
}
delete ref_count;
}
//复制构造函数
my_shared_ptr(const my_shared_ptr& obj) {
m_ptr = obj.m_ptr;
ref_count = obj.ref_count;
if (ref_count != nullptr) {
(*ref_count)++;
}
}
//赋值运算符
my_shared_ptr& operator=(const my_shared_ptr& obj) {
if (obj.m_ptr == m_ptr) {
return *this;
}
if (ref_count != nullptr) {
if (*ref_count == 0) {
delete ref_count;
delete m_ptr;
}
}
m_ptr = obj.m_ptr;
ref_count = obj.ref_count;
if (ref_count != nullptr) {
(*ref_count)++;
}
return *this;
}
//移动构造函数
my_shared_ptr(my_shared_ptr&& obj) :m_ptr(nullptr), ref_count(nullptr) {
printf("移动构造\n");
obj.swap(*this);
}
//移动赋值运算符
my_shared_ptr& operator=(my_shared_ptr&& obj){
printf("移动赋值\n");
my_shared_ptr(std::move(obj)).swap(*this);
return *this;
}
//工具函数
unsigned int use_count() const{
return ref_count != nullptr ? *ref_count : 0;
}
};
template<typename T>
void my_shared_ptr<T>::swap(my_shared_ptr& obj) {
std::swap(m_ptr, obj.m_ptr);
std::swap(ref_count, obj.ref_count);
}
my_shared_ptr.cpp
#include <iostream>
#include "my_shared_ptr.h"
int main()
{
//有参构造函数
int* ptr = new int(100);
my_shared_ptr<int> p2(ptr);
std::cout << "有参构造p2 use_count() = " << p2.use_count() << std::endl;
//复制构造函数
my_shared_ptr<int> p3(p2);
std::cout << "复制构造p3 use_count() = " << p3.use_count() << std::endl;
//赋值运算符
p3 = p2;
std::cout << "p3 use_count() = " << p3.use_count() << std::endl;
std::cout << "p2 use_count() = " << p2.use_count() << std::endl;
//移动复制
my_shared_ptr<int> p4(p3);
std::cout << "p4 use_count() = " << p4.use_count() << std::endl;
my_shared_ptr<int> p5(std::move(p4));
std::cout << "p4 use_count() = " << p4.use_count() << std::endl;
std::cout << "p5 use_count() = " << p5.use_count() << std::endl;
//移动赋值
p4 = std::move(p5);
std::cout << "p5 use_count() = " << p5.use_count() << std::endl;
std::cout << "p4 use_count() = " << p4.use_count() << std::endl;
}
> 结果：
