c++单例

class Lock  
{  
private:         
    CCriticalSection m_cs;  
public:  
    Lock(CCriticalSection  cs) : m_cs(cs)  
    {  
        m_cs.Lock();  
    }  
    ~Lock()  
    {  
        m_cs.Unlock();  
    }  
};  
  
class Singleton  
{  
private:  
    Singleton();  
    Singleton(const Singleton &);  
    Singleton& operator = (const Singleton &);  
  
public:  
    static Singleton *Instantialize();  
    static Singleton *pInstance;  
    static CCriticalSection cs;  
};  
  
Singleton* Singleton::pInstance = 0;  
  
Singleton* Singleton::Instantialize()  
{  
    if(pInstance == NULL)  
    {   //double check   
        Lock lock(cs);           //用lock实现线程安全，用资源管理类，实现异常安全   
        //使用资源管理类，在抛出异常的时候，资源管理类对象会被析构，析构总是发生的无论是因为异常抛出还是语句块结束。   
        if(pInstance == NULL)  
        {  
            pInstance = new Singleton();  
        }  
    }  
    return pInstance;  
}