#include <stdlib.h>
#include <stdio.h>
#include "c:queue.h"

/* initialize queue by setting both front and rear to NULL */
void CreateQueue(Q_TYPE *queue)
{  queue->front=NULL;
   queue->rear=NULL;
}

/* resets queue to empty & returns the elements of the queue to the system */
void DestroyQueue(Q_TYPE *queue)
{  NODE_PTR temp_ptr;

   while ( EmptyQueue(queue) == FALSE)
   {  temp_ptr=queue->front;
      queue->front=queue->front->next;
      free(temp_ptr);
   }
   queue->rear = NULL;
}

/* returns true if front is NULL */
BOOLEAN EmptyQueue(Q_TYPE *queue)
{  if (queue->front == NULL)
      return TRUE;
   else
      return FALSE;
}

/* always returns false */
BOOLEAN FullQueue()
{ NODE_PTR test_ptr = (NODE_PTR) malloc(sizeof(NODE_TYPE));

  if (test_ptr==NULL)
    return TRUE;
  else {
    free(test_ptr);
    return FALSE;
  }
}

/* adds an element to the rear of the queue */
void Enqueue(Q_TYPE *queue, ITEM_TYPE new_item)
{  NODE_PTR new_node;

   new_node=(NODE_PTR) malloc(sizeof(NODE_TYPE));

   new_node->item=new_item;
   new_node->next=NULL;
   if (EmptyQueue(queue)==TRUE)
      queue->front=new_node;
   else  /* if the queue is not empty */
      queue->rear->next=new_node;
   queue->rear=new_node;
}

/* removes an element from the front of the queue */
void Dequeue(Q_TYPE *queue, ITEM_TYPE *front_item)
{  NODE_PTR temp_ptr;

   *front_item=queue->front->item;
   temp_ptr=queue->front;
   queue->front=queue->front->next;

   if (EmptyQueue(queue))
      queue->rear=NULL;

   free(temp_ptr);
}