queue2.template

using queue to solve traffic matter by C++ in linux environment

// FILE: queue2.template
// TEMPLATE CLASS IMPLEMENTED: Queue<Item> (see queue2.h for documentation)
// This file is included in the header file, and not compiled separately.
// INVARIANT for the Queue ADT:
//   1. The number of items in the Queue is stored in the member variable
//      count.
//   2. The items in the queue are stored in a linked list, with the front of
//      the queue stored at the head node, and the rear of the queue stored at
//      the final node.
//   3. The member variable front_ptr is the head pointer of the linked list of
//      items. For a non-empty queue, the member variable rear_ptr is the
//      tail pointer of the linked list; for an empty list, we don't care
//      what's stored in rear_ptr.

#include <assert.h>  // Provides assert
#include <stdlib.h>  // Provides size_t
#include "link2.h"   // Linked list toolkit

template <class Item>
Queue<Item>::Queue( )
// Library facilities used: stdlib.h
{
    count = 0;
    front_ptr = NULL;
}

template <class Item>
Queue<Item>::Queue(const Queue<Item>& source)
// Library facilities used: link2.h
{
    count = source.count;
    list_copy(source.front_ptr, front_ptr, rear_ptr);
}

template <class Item>
Queue<Item>::~Queue( )
{
    list_clear(front_ptr);
}

template <class Item>
void Queue<Item>::operator =(const Queue<Item>& source)
// Library facilities used: link2.h
{
    if (source.front_ptr == front_ptr) // Handle self-assignment
        return;

    list_clear(front_ptr);
    count = source.count;
    list_copy(source.front_ptr, front_ptr, rear_ptr);
}

template <class Item>
void Queue<Item>::insert(const Item& entry)
// Library facilities used: link2.h
{
    if (is_empty( ))
    {   // Insert first entry
        list_head_insert(front_ptr, entry);
        rear_ptr = front_ptr;
    }
    else
    {
        list_insert(rear_ptr, entry);
        rear_ptr = rear_ptr->link;
    }
    count++;
}

template <class Item>
Item Queue<Item>::get_front( )
// Library facilities used: assert.h
{
    Item answer;

    assert(!is_empty( ));
    answer = front_ptr->data;
    list_head_remove(front_ptr);
    count--;    
    return answer;
}

template <class Item>
Item Queue<Item>::peek( ) const 
// Library facilities used: assert.h
{
    assert(!is_empty( ));
    return front_ptr->data;
}