【设计模式】单例模式2

如果多线程下同时进入if(!onlystance)就有可能出现错误。所以显然是需要加入互斥锁的。

class singleStance{
	private :
		singleStance();
	public :
		static singleStance* onlystance;
		static singleStance* getStance(){
			lockBase* lockbase = new lockBase();
			lockBase->lock();
			if(onlystance){
				onlystance = new singleStance();
			}
			lockBase->unlock();
			return onlystance;
		}
	
};
class lockBase{
	protected:
		friend class singleStance;
		CRITICAL_SECTION cs;
	public : 
		lockBase()
		{
			::InitializeCriticalSection(&cs);
		}
		void lock()
		{
			::EnterCriticalSection(&cs);
		}
		void unlock()
		{
			::LeaveCriticalSection(&cs);
		}
		~lockBase(){
			::DeleteCriticalSection(&cs);
		}
};