メッセージをメッセージキューに押し込み、メッセージキューから取り出す---ヘテロチェーンテーブルとC++のマルチステート性を利用する

#include 
using namespace std;

//    id 
typedef enum
{
	ErrorId = -1,
	IntegerId = 1,
	PointId = 2,
	RectangeId = 3,
}ObjectID;


//   
struct Basic
{
	ObjectID id;
	virtual Basic *copy() = 0; //     
};

//    
struct Integer : public Basic
{
	int a;

	Basic *copy()
	{
		Integer *p = new Integer;
		p->a = ((Integer*)this)->a;
		p->id = ((Integer*)this)->id;

		return p;
	}
};

//   
struct Point : public Basic
{
	int x;
	int y;

	Basic *copy()
	{
		Point *p = new Point;
		p->x = ((Point*)this)->x;
		p->y = ((Point*)this)->y;
		p->id = ((Point*)this)->id;

		return p;
	}
};

//    
struct Rectangle : public Basic
{
	Point point;
	int width;
	int height;

	Basic *copy()
	{
		Rectangle *p = new Rectangle;
		p->point.x = ((Rectangle*)this)->point.x;
		p->point.y = ((Rectangle*)this)->point.y;
		p->width = ((Rectangle*)this)->width;
		p->height = ((Rectangle*)this)->height;
		p->id = ((Rectangle*)this)->id;

		return p;
	}
};

//         ，        ，     
typedef struct node
{
	node *next;
	Basic *pBasic;
}Node;


Node *head = NULL;  //       （          ）


//            
Node *addToMsgQueue(Basic* pb)
{
	Node *pn = new Node;
	Node *qn = NULL;
	Basic *p = pb->copy(); //    

	if(NULL == head)
	{
		head = pn;
	}
	else
	{
		qn = head;
		while(NULL != qn->next)
		{
			qn = qn->next;
		}

		qn->next = pn;
	}

	pn->pBasic = p;   //       
	pn->next = NULL;  //       

	return head;
}


//             （  ）
Node *getMsgFromQueue()
{
	if(NULL == head)
	{
		return NULL;
	}

	Node *pn = head;
	head = head->next;

	return pn;
} 



//   : A    B     
int main()
{

	/* A   */

	//          
	Integer i;
	Point po;
	Rectangle rect;

	i.id = IntegerId;
	po.id = PointId;
	rect.id = RectangeId;
	
	i.a = 11;
	po.x = 22;
	po.y = 33;

	rect.point.x = 44;
	rect.point.y = 55;
	rect.width = 66;
	rect.height = 77;


	//       
	addToMsgQueue(&i);
	addToMsgQueue(&po);
	addToMsgQueue(&rect);
	addToMsgQueue(&i);
	addToMsgQueue(&po);
	addToMsgQueue(&rect);



	/* B   */

	Node *p = NULL;

	//           
	while(1)
	{
		p = getMsgFromQueue();
		if(NULL == p)
		{
			//         
			continue;
		}

		//   A,B       ，        
		switch(p->pBasic->id) 
		{
			case IntegerId:
			{
				cout << ((Integer*)(p->pBasic))->a << endl;
				break;
			}
			case PointId:
			{
			
				cout << ((Point *)(p->pBasic))->x << endl;
				cout << ((Point *)(p->pBasic))->y << endl;
				break;
			}
			case RectangeId:
			{
				cout << ((Rectangle *)(p->pBasic))->point.x << endl;
				cout << ((Rectangle *)(p->pBasic))->point.y << endl;
				cout << ((Rectangle *)(p->pBasic))->width << endl;
				cout << ((Rectangle *)(p->pBasic))->height << endl;
				break;
			}
			default:
			{
				break;
			}
		}
	}

	return 0;
}