C++实现一个线程安全的单例工厂实现代码
我们见到经常有人用 static 局部对象的方式实现了类似单例模式,最近发现一篇文章明确写明 编译器在处理 static局部变量的时候 并不是线程安全的 ！！！
http://blogs.msdn.com/b/oldnewthing/archive/2004/03/08/85901.aspx
于是实现了一个单例工厂 并且是线程安全的
#ifndef SINGLETONFACTORY_H
#define SINGLETONFACTORY_H
#include "windows.h"
#include <memory>
namespace Tools
{
template<class T>class SingletonFactory
{
public:
virtual ~SingletonFactory()
{
::DeleteCriticalSection(&__criticalSection);
}
std::auto_ptr<T>& GetInstance();
static SingletonFactory<T>* CreateSingletonFactory();
private:
SingletonFactory()
{
::InitializeCriticalSection(&__criticalSection);
}
std::auto_ptr<T> __singletonObj;
CRITICAL_SECTION __criticalSection;
};
//初始化创建 后续在多线程中使用
//还有另一种写法是单独的函数直接返回内部单例包装静态成员在 多线程情况下不安全
//SingletonFactory::CreateSingletonFactory().GetInstance();
template<class T> SingletonFactory<T>* SingletonFactory<T>::CreateSingletonFactory(){
static SingletonFactory<T> temObj;
return &temObj;
}
//工厂实例
template<class T> std::auto_ptr<T>& SingletonFactory<T>::GetInstance()
{
if(__singletonObj.get()==0)
{
::EnterCriticalSection(&__criticalSection);
if(__singletonObj.get()==0)
__singletonObj=std::auto_ptr<T>(new T);
::LeaveCriticalSection(&__criticalSection);
}
return __singletonObj;
}
}
#endif // SINGLETONFACTORY_H
测试代码
SingletonFactory<Data1>*singleton1=SingletonFactory<Data1>::CreateSingletonFactory(); singleton1->GetInstance()->x=100; cout<<singleton1->GetInstance()->x<<endl; singleton1->GetInstance()->y=200; cout<<singleton1->GetInstance()->x<<endl; cout<<singleton1->GetInstance()->y<<endl; SingletonFactory<Data2>*singleton2=SingletonFactory<Data2>::CreateSingletonFactory(); singleton2->GetInstance()->x=100; cout<<singleton2->GetInstance()->x<<endl; singleton2->GetInstance()->y=200; cout<<singleton2->GetInstance()->x<<endl; cout<<singleton2->GetInstance()->y<<endl;
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