《C语言编程实例 —— 函数参数为函数，作为回调函数》

1.

typedef int (*GET_VIDEO_FLAG_CALLBACK)(void* param);
typedef struct {
    volatile int8_t pm_lock_ref;
    pthread_mutex_t pm_lock_mutex;
    pthread_t pm_task;
    GET_VIDEO_FLAG_CALLBACK on_get_video_flag;
} power_manager_t;

static power_manager_t power_ctx;

static int on_get_video_flag(void* param) {
    tag_CAT_CONTEXT* cat_ctx = param;

    return cat_ctx->is_have_video;
}

yd_power_manager_init(on_get_video_flag);

int yd_power_manager_init(int (*on_get_video_flag)(void* param)) {
    int ret = 0;
    pthread_attr_t attr;

    memset(&power_ctx, 0, sizeof(power_manager_t));
    power_ctx.pm_lock_ref = 0;
    power_ctx.on_get_video_flag = on_get_video_flag;
    pthread_mutex_init(&power_ctx.pm_lock_mutex, NULL);

    pthread_attr_init(&attr);
    pthread_attr_setstacksize(&attr, 0x1000);
    pthread_create(&power_ctx.pm_task, &attr, run_pm_task, &power_ctx);
    pthread_attr_destroy(&attr);

    return ret;
}

static void* run_pm_task(void* arg) {
    power_manager_t* power_ctx = (power_manager_t*)arg;
    if (power_ctx == NULL) {
        return NULL;
    }
    arch_os_queue_t msg_quene_id = get_msg_queque_id();

    prctl(PR_SET_NAME, "pm");
    pthread_detach(pthread_self());
while (1) {if (power_ctx == NULL) {
            break;
        }

        if (power_ctx->pm_lock_ref == 0 && get_is_battery_powered()) {
            printf("power down %llu ms\n", arch_os_ms_now());
            send_message(msg_quene_id, CAT_MSG_POWER_DOWN_REQ);
        }
    }

    return NULL;
}


int yd_pm_power_down(void* cat_ctx, int* isOsdupdating) {
    int ret = 0;
    uint8_t is_have_video = 0;

　　 //该函数直接调用，判断返回值
    if (power_ctx.on_get_video_flag) {
       xxxx；
    }
    return ret;
}