async queue:add api about length

include/neuron/utils/async_queue.h

@@ -87,4 +87,6 @@ void neu_async_queue_remove(neu_async_queue_t *q, neu_async_queue_filter filter,
  */
 void neu_async_queue_clean(neu_async_queue_t *q);
 
+int neu_async_queue_len(neu_async_queue_t *q);
+
 #endif

src/utils/async_queue.c

@@ -159,4 +159,16 @@ void neu_async_queue_clean(neu_async_queue_t *q)
         free(el);
     }
     pthread_mutex_unlock(&q->mtx);
+}
+
+int neu_async_queue_len(neu_async_queue_t *q)
+{
+    int      count = 0;
+    element *elt   = NULL;
+
+    pthread_mutex_lock(&q->mtx);
+    DL_COUNT(q->list, elt, count);
+    pthread_mutex_unlock(&q->mtx);
+
+    return count;
 }