模拟实现auto_ptr、scoped_ptr、shared_ptr等智能指针

智能指针：所谓智能指针就是智能/自动化的管理指针所指向的动态资源的释放。

auto_ptr 有缺陷，自己赋值给自己，会失效置空

scoped_ptr 解决了auto_ptr缺陷，防拷贝

shared_ptr 含有引用计数 weak_ptr打破循环引用，不增加引用计数

#include<iostream>
using namespace std;

//模拟auto_ptr
template<class T>
class SmartPtr
{
public:
SmartPtr(T* ptr = NULL)
:_ptr(ptr)
{}
SmartPtr(SmartPtr<T>& sp)
{
_ptr = sp._ptr;
sp._ptr = NULL;
}
SmartPtr<T>& operator=(SmartPtr<T>& sp)
{
if (this != &sp)
{
_ptr = sp._ptr;
sp._ptr = NULL;
}
return *this;
}
~SmartPtr()
{
if (_ptr)
{
delete _ptr;
}
}
T* operator->()
{
return _ptr;
}
T& operator*()
{
return *_ptr;
}
private:
T* _ptr;
};

class AA
{
public:
AA()
{
cout<<"AA()"<<endl;
}

~AA()
{
cout<<"~AA()"<<endl;
}
void Print()
{
cout<<"Print()"<<endl;
}
public:
int _aa;
};
void Test1()
{
SmartPtr<AA> p1(new AA);
SmartPtr<AA> p2(p1);
SmartPtr<AA> p3;
p3 = p2;
p1->Print();
(*p3).Print();
}
int main()
{
Test1();
system("pause");
return 0;
}

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

//模拟scoped_ptr
template<class T>
class SmartPtr
{
public:
SmartPtr(T* ptr = NULL)
:_ptr(ptr)
{}

~SmartPtr()
{
if (_ptr)
{
delete _ptr;
}
}
T* operator->()
{
return _ptr;
}
T& operator*()
{
return *_ptr;
}
private:
SmartPtr(SmartPtr<T>& sp)
{
_ptr = sp._ptr;
sp._ptr = NULL;
}
SmartPtr<T>& operator=(SmartPtr<T>& sp)
{
if (this != &sp)
{
_ptr = sp._ptr;
sp._ptr = NULL;
}
return *this;
}
private:
T* _ptr;
};

class AA
{
public:
AA()
{
cout << "AA()" << endl;
}

~AA()
{
cout << "~AA()" << endl;
}
void Print()
{
cout << "Print()" << endl;
}
public:
int _aa;
};
void Test2()
{
SmartPtr<AA> p1(new AA);
SmartPtr<AA> p3;
p1->Print();
(*p3).Print();
}
int main()
{
Test2();
system("pause");
return 0;
}

#include<iostream>
using namespace std;

//模拟shared_ptr
template<class T>
class SmartPtr
{
public:
SmartPtr(T* ptr = NULL)
:_ptr(ptr)
, _CountPtr(new int(1))
{
(*_CountPtr)++;
}
SmartPtr(SmartPtr<T>& sp)
{
_ptr = sp._ptr;
_CountPtr = sp._CountPtr;
(*_CountPtr)++;
}
SmartPtr<T>& operator=(SmartPtr<T>& sp)
{
if (this != &sp)
{
if (--(*_CountPtr) && _ptr)
{
delete _ptr;
delete _CountPtr;
}
_ptr = sp._ptr;
_CountPtr = sp._CountPtr;
(*_CountPtr)++;
}
return *this;
}
~SmartPtr()
{
if (--(*_CountPtr)&&_ptr)
{
delete _ptr;
delete _CountPtr;
}
}
int GetRefCount()
{
return *_CountPtr;
}
T* operator->()
{
return _ptr;
}
T& operator*()
{
return *_ptr;
}
private:
T* _ptr;
int* _CountPtr;//指向引用计数的指针
};

class AA
{
public:
AA()
{
cout << "AA()" << endl;
}

~AA()
{
cout << "~AA()" << endl;
}
void Print()
{
cout << "Print()" << endl;

}
public:
int _aa;
};
void Test3()
{
SmartPtr<AA> p1(new AA);
SmartPtr<AA> p2(p1);
SmartPtr<AA> p3;
p3 = p2;
p1->Print();
(*p3).Print();
}
int main()
{
Test3();
system("pause");
return 0;
}