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;
}