queue.c

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
#include"queue.h"

static void  CopyToNode(Item item, Node* pn);
static void CopyToItem(Node* pi,Item * item );




void InitializeQueue( Queue * pq)
{
	pq->front = NULL;
	pq->rear = NULL;
	pq->items = 0;
}

bool QueueIsFull(const Queue* pq)
{
	return(pq->items == MAXQUEUE);
}

bool QueueIsEmpty(const Queue* pq)
{
	return(pq->items == 0);
}

int QueueItemCount(const Queue* pq)
{
	return pq->items;
}

bool EnQueue(Item item,Queue* pq)
{
	Node* pnew;

	if (QueueIsFull(pq))
		return false;
	pnew = (Node*)malloc(sizeof(Node));
	if (pnew == NULL)
	{
		fprintf(stderr, "Unable to allocate memory!\n");
		exit(1);
	}
	CopyToNode(item, pnew);
	pnew->next = NULL;
	if (QueueIsEmpty(pq))
	{
		pq->front = pnew;
	}
	else
	{
		pq->rear->next = pnew;
	}
	pq->rear = pnew;
	pq->items++;

	return true;
}



bool DeQueue(Item* pitem, Queue* pq)
{
	Node* pt;
	if (QueueIsEmpty(pq))
		return false;
	CopyToItem(pq->front, pitem);
	pt = pq->front;
	pq->front = pq->front->next;
	free(pt);
	pq->items--;
	if (pq->items == 0)
	{
		pq->rear = NULL;
	}
	return true;
}

void EmptyTheQueue(Queue* pq)
{
	Item dummy;
	while (!QueueIsEmpty(pq))
	{
		DeQueue(&dummy, pq);
	}
}

static void CopyToNode(Item item, Node* pn) {
	pn->item = item;
}

static void CopyToItem(Node* pn, Item* pi)
{
	*pi = pn->item;
}