智能指针的实例

一时失言乱红尘 2022-04-11 05:30 191阅读 0赞

#include <iostream>
    #include <windows.h>
    using namespace std;
    
    #define SAFE_DELETE(p) if (p) { delete p; p = NULL; }
    
    class KRefCount
    {
       
    public:
        KRefCount():m_nCount(0){}
    
    public:
    	unsigned AddRef(){ return InterlockedIncrement(&m_nCount); }
    	unsigned Release(){ return InterlockedDecrement(&m_nCount); }
        void Reset(){ m_nCount = 0; }
    
    private:
        unsigned long m_nCount;
    };
    
    template <typename T>
    class SmartPtr
    {
       
    public:
        SmartPtr(void)
            : m_pData(NULL)
        {
       
            m_pReference = new KRefCount();
            m_pReference->AddRef();
        }
    
        SmartPtr(T* pValue)
            : m_pData(pValue)
        {
       
            m_pReference = new KRefCount();
            m_pReference->AddRef();
        }
    
        SmartPtr(const SmartPtr<T>& sp)
            : m_pData(sp.m_pData)
            , m_pReference(sp.m_pReference)
        {
       
            m_pReference->AddRef();
        }
    
        ~SmartPtr(void)
        {
       
            if (m_pReference && m_pReference->Release() == 0)
            {
       
                SAFE_DELETE(m_pData);
                SAFE_DELETE(m_pReference);
            }
        }
    
        inline T& operator*()
        {
       
            return *m_pData;
        }
    
        inline T* operator->()
        {
       
            return m_pData;
        }
    
        SmartPtr<T>& operator=(const SmartPtr<T>& sp)
        {
       
            if (this != &sp)
            {
       
                if (m_pReference && m_pReference->Release() == 0)
                {
       
                    SAFE_DELETE(m_pData);
                    SAFE_DELETE(m_pReference);
                }
    
                m_pData = sp.m_pData;
                m_pReference = sp.m_pReference;
    			m_pReference->AddRef();
            }
    
            return *this;
        }
    
        SmartPtr<T>& operator=(T* pValue)
        {
       
            if (m_pReference && m_pReference->Release() == 0)
            {
       
                SAFE_DELETE(m_pData);
                SAFE_DELETE(m_pReference);
            }
    
            m_pData = pValue;
            m_pReference = new KRefCount;
    		m_pReference->AddRef();
            return *this;
        }
    
        T* Get()
        {
       
            T* ptr = NULL;        
            ptr = m_pData;
    
            return ptr;
        }
    
        void Attach(T* pObject)
        {
       
            if (m_pReference->Release() == 0)
            {
       
                SAFE_DELETE(m_pData);
                SAFE_DELETE(m_pReference);
            }
    
            m_pData = pObject;
            m_pReference = new KRefCount;
            m_pReference->AddRef();
        }
    
        T* Detach()
        {
       
            T* ptr = NULL;
    
            if (m_pData)
            {           
                ptr = m_pData;
                m_pData = NULL;
                m_pReference->Reset();
            }
            return ptr;
        }
    
    private:
        KRefCount* m_pReference;
        T* m_pData;
    };
    
    class CTest
    {
       
    public:
    	CTest(int b) : a(b) {}
    private:
    	int a;
    };
    
    int main()
    {
       
    	SmartPtr<CTest> pSmartPtr1(new CTest(10));
    	SmartPtr<CTest> pSmartPtr2(new CTest(20));
    
    	pSmartPtr1 = pSmartPtr2;
    }