双向链表快速实现一个通用队列

直接贴代码了，实践中也经常用到，没必要每次都自己写。

struct queue{
    void *prev;
    void *next;
    int count;
    enum queuestate state;
    pthread_mutex_t mutex;
    pthread_cond_t cond;
};
//初始化
static inline void init_queue(struct queue *q)
{
    q->prev = q->next = q;
    q->count = 0;
    pthread_mutex_init(&q->mutex, NULL);
    pthread_cond_init(&q->cond, NULL);
}

//入队
static inline void enqueue(struct link_list *item, struct queue *q_head)
{
    if (item == NULL) {
        return;
    }
    pthread_mutex_lock(&q_head->mutex);
    struct link_list *q_tail = NULL;
    q_tail = q_head->prev;

    ((struct link_list *)item)->prev = q_tail;
    ((struct link_list *)item)->next = q_head;
    q_tail->next = item;
    q_head->prev = item;

    q_head->count++;

    pthread_cond_signal(&q_head->cond);
    pthread_mutex_unlock(&q_head->mutex);
    return;
}
//出队
static inline void *dequeue(struct queue *q_head)
{
    struct link_list *q_item = NULL, *next = NULL;

    pthread_mutex_lock(&q_head->mutex);

    while (0 == q_head->count) {
        pthread_cond_wait(&q_head->cond, &q_head->mutex);
    }

    q_item = q_head->next;
    next = q_item->next;

    q_head->next = q_item->next;
    next->prev = q_item->prev;

    q_head->count--;

    q_item->prev  = NULL;
    q_item->next = NULL;

    pthread_mutex_unlock(&q_head->mutex);

    return q_item;
}
struct my_msg {
    void *prev;
    void *next;

    char data[MAX_MSG_SIZE];
    int len;
};

int main()
{
    struct queue mqtt_send;
    init_queue(&mqtt_send);

    struct my_msg *test = (struct my_msg *)malloc(sizeof(struct my_msg));
    //入队
    enqueue(&mqtt_send, test);
    //出队
    struct my_msg *newtest =  (struct my_msg *)dequeue(&mqtt_send);
    return 0;       
}