// Programmed by Anthony Barbachan
// Programmed in Turbo C++ 3.0
// Note: This is the header file for the object library Queue
// Purpose: To provide a Queue for ObjectBase associated data type.

// Version 1.00
// Last Modified On 7/10/95
// Version 1.10
// Last Modified On 12/30/97
// Purpose: Added a Peek function for the rear object

#ifndef __QUEUE_HPP__
#define __QUEUE_HPP__

#include <limits.h>
#include "object.hpp"

//////////////////////////////////////////////////////////////////////////////

// This class provides a Queue for any ObjectBase associated object.

template <class ObjectType>
class QueueOf
{
	protected:
		ObjectType* front;
		ObjectType* back;
		unsigned long count;
	public:
		QueueOf() { front = NULL; count = 0ul; }
		~QueueOf() { Flush(); }
		int Put(ObjectType* obj);
		ObjectType* Get(void);
		void Flush(void);
		ObjectType* Peek() { return front; }
		ObjectType* RearPeek() { return back; }
		int IsEmpty() { return front == NULL; }
		int NotEmpty() { return front != NULL; }
		int IsNotEmpty() { return front != NULL; }
		unsigned long NumObjects() { return count; }
		int operator ! () { return IsEmpty(); }
};

///////////////////////////////////////***************************************

///////////////////////////////////////***************************************

// This function Puts an object onto the queue

template <class ObjectType>
int QueueOf<ObjectType>::Put(ObjectType* obj)
{
	if((count < ULONG_MAX) && (obj != NULL))
	{
		if(NotEmpty())				// If the Queue is not empty
		{
			back->LinkNext(obj);	// Link obj after the last object
			back = obj;			// Make obj the new last object
		}
		else						// If the Queue is empty
			front = back = obj;		// Start a Queue with Object obj

		count++;					// Incriment counter
		return 1;
	}
	else	    						// If unable to complete operation
		return 0;
}

///////////////////////////////////////***************************************

// This function Gets an object from the Queue

template <class ObjectType>
ObjectType* QueueOf<ObjectType>::Get()
{
	if(NotEmpty())					// If the Queue is not empty
	{
		ObjectType* temp = front;	// Save address of the first object
		front = (ObjectType *) temp->UnLinkNext();	// Unlink old front and set new front
		count--;					// Deincriment counter
		return temp;				// Return old first object
	}
	else							// If the Queue is empty
		return NULL;
}

///////////////////////////////////////***************************************

template <class ObjectType>
void QueueOf<ObjectType>::Flush()
{
	ObjectType* temp = NULL;

	while(front != NULL)			// While the Queue is not empty
	{
		temp = front;				// Save address of the first object
		front = (ObjectType *) temp->UnLinkNext();	// Unlink old front and set new front
		delete temp;
	}

	back = NULL;					// Secure back pointer
	count = 0ul;					// Reset counter
}

///////////////////////////////////////***************************************

#endif