/* The basic queue routines. */

#include "queue.h"

void initialize(queue *q)
{
   q -> cnt = 0;
   q -> front = NULL;
   q -> rear = NULL;
}

data dequeue(queue *q)
{ 
   data   d;
   elem   *p;

   d = q -> front -> d;
   p = q -> front;
   q -> front = q -> front -> next;
   q -> cnt--;
   free(p);
   return d;
}

void enqueue(data d, queue *q)
{
   elem   *p;

   p = malloc(sizeof(elem));
   p -> d = d;
   p -> next = NULL;
   if (!empty(q)) {
      q -> rear -> next = p;
      q -> rear = p;
   }
   else
      q -> front = q -> rear = p;
   q -> cnt++;
}

data front(const queue *q)
{
   return (q -> front -> d);
}

boolean empty(const queue *q)
{
   return ((boolean) (q -> cnt == EMPTY));
}

boolean full(const queue *q)
{
   return ((boolean) (q -> cnt == FULL));
}