循环队列数组实现

循环队列的数组实现：

#ifndef QUEUE_H
#define QUEUE_H

typedef int ElementType;

struct QueueRecord;
typedef struct QueueRecord *Queue;

int IsEmpty(Queue q);
int IsFull(Queue q);
Queue CreateQueue(int maxElements);
void DisposeQueue(Queue q);
void MakeEmpty(Queue q);
int Enqueue(ElementType x, Queue q);
int Dequeue(Queue q);
ElementType Front(Queue q);
ElementType FrontAndDequeue(Queue q);

#endif

queue.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "queue.h"

#define SAFE_FREE(q) {if (q) {free(q); q = NULL;}}

struct QueueRecord
{
    int capacity;
    int front;
    int rear;
    int size;
    ElementType *array;
};

int IsEmpty(Queue q)
{
    return q->size == 0;
}

int IsFull(Queue q)
{
    return q->size == q->capacity;
}

Queue CreateQueue(int maxElements)
{
    Queue q = malloc(sizeof(struct QueueRecord));
    if (q == NULL)
    {
        fprintf(stderr, "create queue failed.");
        return NULL;
    }
    q->array = malloc(maxElements * sizeof(char));
    if (q->array == NULL)
    {
        fprintf(stderr, "create queue failed.");
        return NULL;
    }
    q->capacity = maxElements;
    q->front = q->rear = 0;
    q->size = 0;

    return q;
}

void DisposeQueue(Queue q)
{
    if (q == NULL)
    {
        fprintf(stderr, "the queue is NULL.");
        return;
    }
    SAFE_FREE(q->array);
    SAFE_FREE(q);
}

void MakeEmpty(Queue q)
{
    if (q == NULL)
    {
        fprintf(stderr, "the queue is NULL.");
        return;
    }
    q->front = q->rear = 0;
    q->size = 0;
    memset(q->array, 0x00, q->capacity);
}

int Enqueue(ElementType x, Queue q)
{
    if (IsFull(q))
    {
        fprintf(stderr, "queue is full.");
        return -1;
    }
    if (IsEmpty(q))
    {
        q->array[q->front] = x;
    }
    else
    {
        if ((q->rear + 1) == q->capacity)
        {
            q->rear = 0;
            q->array[q->rear] = x;
        }
        else
        {
            q->array[++q->rear] = x;
        }
    }
    q->size++;
    printf("size = %d\n", q->size);

    return 0;
}

int Dequeue(Queue q)
{
    if (IsEmpty(q))
    {
        fprintf(stderr, "queue is empty.");
        return -1;
    }

    q->array[q->front] = 0;
    if ((q->front + 1) == q->capacity) 
    {
        q->front = 0;
    }
    else
    {
        q->front++;
    }
    q->size--;
    return 0;
}

ElementType Front(Queue q)
{
    if (q == NULL)
    {
        fprintf(stderr, "queue is empty.");
        return -1;
    }
    return q->array[q->front];
}