// Source: "Software Design ...", John A Robinson, Newnes, 2004, page 211.
class queue
	{
	// First come the private data items
	int queue_length;		// To allow the caller to set max length
	itemtype **queue_base;		// Points to where queue is in memory
	int head;
	int tail;
public:
	queue(int size)				
		{
		queue_base = new itemtype *[queue_length = size];	
		head = tail = 0;
		};
	~queue()									
		{
		delete [] queue_base;
		}
	int enqueue(itemtype *);
	int dequeue(itemtype **);
	};

int queue::enqueue(itemtype *value)		
		{
		if ((tail == head-1)||((tail == queue_length-1)&&(head == 0)))
			return(-1);		// Queue full
		queue_base[tail++] = value;
		if (tail == queue_length)	// Wrap around to start of array
			tail = 0;
		return(0);
		}
int queue::dequeue(itemtype **value)
		{
		if (head == tail)
			return(-1);		// Queue empty
		*value = queue_base[head++];
		if (head == queue_length)	// Wrap around to start of array
			head = 0;
		return(0);
		}