// queuetp.h -- queue template with a nested class
#ifndef QUEUETP_H_
#define QUEUETP_H_
template <class Item>
class QueueTP
{
private:
enum {Q_SIZE = 10};
// Node is a nested class definition
class Node
{
public:
Item item;
Node * next;
Node(const Item & i):item(i), next(0){ }
};
Node * front; // pointer to front of Queue
Node * rear; // pointer to rear of Queue
int items; // current number of items in Queue
const int qsize; // maximum number of items in Queue
QueueTP(const QueueTP & q) : qsize(0) {}
QueueTP & operator=(const QueueTP & q) { return *this; }
public:
QueueTP(int qs = Q_SIZE);
~QueueTP();
bool isempty() const
{
return items == 0;
}
bool isfull() const
{
return items == qsize;
}
int queuecount() const
{
return items;
}
bool enqueue(const Item &item); // add item to end
bool dequeue(Item &item); // remove item from front
};
// QueueTP methods
template <class Item>
QueueTP<Item>::QueueTP(int qs) : qsize(qs)
{
front = rear = 0;
items = 0;
}
template <class Item>
QueueTP<Item>::~QueueTP()
{
Node * temp;
while (front != 0) // while queue is not yet empty
{
temp = front; // save address of front item
front = front->next;// reset pointer to next item
delete temp; // delete former front
}
}
// Add item to queue
template <class Item>
bool QueueTP<Item>::enqueue(const Item & item)
{
if (isfull())
return false;
Node * add = new Node(item); // create node
if (add == NULL)
return false; // quit if none available
items++;
if (front == 0) // if queue is empty,
front = add; // place item at front
else
rear->next = add; // else place at rear
rear = add; // have rear point to new node
return true;
}
// Place front item into item variable and remove from queue
template <class Item>
bool QueueTP<Item>::dequeue(Item & item)
{
if (front == 0)
return false;
item = front->item; // set item to first item in queue
items--;
Node * temp = front; // save location of first item
front = front->next; // reset front to next item
delete temp; // delete former first item
if (items == 0)
rear = 0;
return true;
}
#endif