C++设计模式之代理模式

#include <iostream>
using namespace std;
 
#define SAFE_DELETE(p) if (p) { delete p; p = NULL;}
 
class CSubject
{
public:
    CSubject(){};
    virtual ~CSubject(){}
 
    virtual void Request() = 0;
};
 
class CRealSubject : public CSubject
{
public:
    CRealSubject(){}
    ~CRealSubject(){}
 
    void Request()
    {
        cout<<"CRealSubject Request"<<endl;
    }
};
 
class CProxy : public CSubject
{
public:
    CProxy() : m_pRealSubject(NULL){}
    ~CProxy()
    {
        SAFE_DELETE(m_pRealSubject);
    }
 
    void Request()
    {
        if (NULL == m_pRealSubject)
        {
            m_pRealSubject = new CRealSubject();
        }
        cout<<"CProxy Request"<<endl;
        m_pRealSubject->Request();
    }
 
private:
    CRealSubject *m_pRealSubject;
};
 
int main()
{
    CSubject *pSubject = new CProxy();
    pSubject->Request();
    SAFE_DELETE(pSubject);
}

#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;
}