智能指针

智能指针

    智能指针就是利用构造函数构造，出了域之后利用类的性质自动调用析构函数析构，解决了指针的内存泄漏问题，省去抛出异常语句

指针

1.auto_ptr

template
class AutoPtr
{
public:
                AutoPtr( T* ptr )
                                :_ptr( ptr)
                {
                }
                ~AutoPtr()
                {
                                 if (_ptr != NULL)
                                {
                                                cout << "delete" << _ptr << endl;
                                                 delete _ptr;
                                                _ptr = NULL;
                                }
                }
                AutoPtr( AutoPtr&ap)
                                :_ptr( ap._ptr)
                {
                                 ap._ptr = NULL;//管理权转移
                }

                 AutoPtr&operator=(AutoPtr< T>&ap )
                {
                                 if (this != &ap)//检测是否自赋值
                                {
                                                cout << "delete=" << _ptr << endl;
                                                 delete _ptr;//删除指向空间

                                                _ptr = ap._ptr;//指向另一块空间
                                                 ap._ptr = NULL;//指针指向空
                                                 return *this ;
                                }
                }
                 T& operator*()
                {
                                 return *_ptr;
                }
                 T*operator->()
                {
                                 return _ptr;
                }
private:
                 T* _ptr;
};
struct A
{
                 int _a;
};
int main()
{
                 AutoPtr ap1(new int(1));
                 AutoPtr ap2(ap1);
                 AutoPtr ap3(new int(2));
                ap3 = ap2;
                *ap3 = 3;
                 AutoPtr ap4(new A);
                ap4->_a = 10;
                 return 0;
}

2.scoped指针

template
class ScopedPtr
{
public:
                ScopedPtr( T* ptr )
                                :_ptr( ptr)
                {
                }

                ~ScopedPtr()
                {
                                 if (_ptr != NULL)
                                {
                                                 delete _ptr;
                                }
                }

                 T&operator*()
                {
                                 return *_ptr;
                }

                 T*operator->()
                {
                                 return _ptr;
                }

protected:
                ScopedPtr( ScopedPtr&sp);
                 ScopedPtr operator=(ScopedPtr &sp);
                 //只声明(声明后系统不会自动生成)不实现，且属于保护成员（或声明为私有成员），故在类外成员不能实现赋值语句，类外也不能实现这个函数
private:
                 T* _ptr;
};
struct A
{
                 int _a;
};
int main()
{
                 ScopedPtrsp1(new int(1));
                 //ScopedPtrsp2(sp1);
                *sp1 = 10;
                 ScopedPtrsp2(new A);
                sp2->_a = 10;

                 //ScopedPtrsp2=sp1;
                 return 0;
}

scoped数组

template
class ScopedArray
{
public:
                ScopedArray( T *ptr )
                                : _ptr( ptr)
                {}
                ~ScopedArray()
                {
                                 if (_ptr!=NULL )
                                {
                                                 delete[]_ptr;
                                }
                }
                 T& operator[](size_t index)
                {
                                 return _ptr[index ];
                }
protected:
                ScopedArray( ScopedArray&sp);
                 ScopedArray&operator=(ScopedArray< T>&sp);
private:
                 T *_ptr;
};

3.shared指针

template
class SharedPtr
{
public:
                SharedPtr( T*ptr )
                                :_ptr( ptr)
                                , _pCount( new int (1))
                {}
                ~SharedPtr()
                {
                                DeleteCount();
                }
                SharedPtr( const SharedPtr & sp)
                                :_ptr( sp._ptr)
                                , _pCount( sp._pCount)
                {
                                ++(*_pCount);
                }
                 SharedPtr& operator=(const SharedPtr< T>& sp )
                {
                                
                                 //1.自赋值
                                 //2.两个对象管理同一块空间
                                 //3.两个对象两个空间
                                 if (_ptr != sp ._ptr)
                                {
                                                DeleteCount();
                                                _ptr = sp._ptr;
                                                _pCount = sp._pCount;
                                                ++(*_pCount);
                                }
                               
                                return*this；
                }
                                /*
                                
                                swap(_ptr, sp._ptr);
                                swap(_pCount, sp._pCount);
                                 */
                 T &operator*()
                {
                                 return *_ptr;
                }
                 T *operator->()
                {
                                 return _ptr;
                }
private:
                 void DeleteCount()
                {
                                 if (--(*_pCount) == 0)
                                {
                                                 delete _ptr;
                                                 delete _pCount;
                                }
                }
private:
                 T* _ptr;
                 int* _pCount;
};
struct A
{
                 int _a;
};
int main()
{
                 SharedPtr sp1(new int(1));
                 SharedPtrsp2(new int(2));
                 SharedPtrsp3(sp1);
                sp3 = sp2;
                 SharedPtrsp4(new int(3));
                *sp4 = 10;
                 SharedPtrsp5(new A);
                sp5->_a = 20;
                getchar();

                 return 0;
}