翻转队列的实现

template<typename _OBJ>
class SwappingList
{
public:
	size_t Add(_OBJ & obj )
	{
		ResGuard<Mutex> lock(m_frontMutex);
		m_frontList->push_back(obj);
		return m_frontList->size();
	}
 
	bool Get(_OBJ & obj )
	{
		if ( m_backList->empty() )
		{
			Swap();
		}
		if ( m_backList->empty() )
		{
			return false;
		}
		obj = m_backList->front();
		m_backList->pop_front();
		return true;
	}
 
	void Swap()
	{
		ResGuard<Mutex> lock(m_frontMutex);
		PRODUCT_LIST * p = m_backList;
		m_backList = m_frontList;
		m_frontList = p;
	}
 
	SwappingList()
	{
		m_frontList = new PRODUCT_LIST;
		m_backList  = new PRODUCT_LIST;
	}
 
	virtual ~SwappingList()
	{
		if ( m_frontList )
		{
			delete m_frontList;
			m_frontList = 0;
		}
		if ( m_backList )
		{
			delete m_backList;
			m_backList = 0;
		}
	}
 
protected:
	typedef std::list<_OBJ>   PRODUCT_LIST;
	PRODUCT_LIST*        m_frontList;
	PRODUCT_LIST*        m_backList;
	Mutex                m_frontMutex;
}