循环队列

#include <stdio.h>
#include <stdlib.h>

#define DEBUG  1

typedef struct _queue_ {
    int *data;
    int head;
    int tail;
    int tlen;
}queue_t;

queue_t *queue_init(int len);
void queue_destory(queue_t *queue);
int queue_enqueue(queue_t *queue, int value);
int queue_dequeue(queue_t *queue, int *value);
int queue_isempty(queue_t *queue);
int queue_isfull(queue_t *queue);
int queue_getlen(queue_t *queue);
#if DEBUG
void _queue_debug_(queue_t *queue);
#endif

int main()
{
    int value = 100;
    queue_t *queue = NULL;

    queue = queue_init(10);

    puts("Enqueue:");
    while (-1 != queue_enqueue(queue, value)) {
        printf("%5d", value);
        value += 100;
    }
    putchar('\n');

    printf("Clen: %d\n", queue_getlen(queue));

#if DEBUG
    _queue_debug_(queue);
#endif

    puts("Dequeue:");
    while (-1 != queue_dequeue(queue, &value))
        printf("%5d", value);
    putchar('\n');

#if DEBUG
    _queue_debug_(queue);
#endif

    queue_destory(queue);
    return 0;
}

queue_t *queue_init(int len)
{
    queue_t *queue = NULL;

    queue = (queue_t *)malloc(sizeof(queue_t));
    queue->tlen = len;
    queue->head = 0;
    queue->tail = 0;
    queue->data = (int *)malloc(sizeof(int) * len);

    return queue;
}

void queue_destory(queue_t *queue)
{
    free(queue->data);
    free(queue);
}

int queue_enqueue(queue_t *queue, int value)
{
    if (queue_isfull(queue))
        return -1;

    queue->data[queue->tail] = value;
    queue->tail = (queue->tail + 1) % queue->tlen;

    return 0;
}

int queue_isfull(queue_t *queue)
{
    if ((queue->tail + 1) % queue->tlen == queue->head)
        return 1;
    return 0;
}

int queue_dequeue(queue_t *queue, int *value)
{
    if (queue_isempty(queue))
        return -1;

    *value = queue->data[queue->head];
    queue->head = (queue->head + 1) % queue->tlen;

    return 0;
}

int queue_isempty(queue_t *queue)
{
    if (queue->head == queue->tail)
        return 1;
    return 0;
}

int queue_getlen(queue_t *queue)
{
    if (queue->head == queue->tail)
        return 0;
    else if (queue->tail > queue->head)
        return queue->tail - queue->head;
    else
        return queue->tlen - queue->head + queue->tail;
}

#if DEBUG
void _queue_debug_(queue_t *queue)
{
    int index;

    puts("--------------- QUEUE_DEBUG -------------------");
    printf("tlen: %d\thead: %d\ttail: %d\n",
            queue->tlen, queue->head, queue->tail);
    for (index = 0; index < queue->tlen; index++)
        printf("%5d", queue->data[index]);
    puts("\n-----------------------------------------------");
}
#endif