#include "kpl.h"

extern inline void kpl_object_queue_init(kpl_object_queue *object_queue);

extern inline void kpl_object_queue_enqueue(kpl_object_queue *object_queue, void *object);

void *kpl_object_queue_dequeue(kpl_object_queue *object_queue) {
    kpl_object *object = NULL;
    for (;;) {
        kpl_object *tail = object_queue->tail, *queue_next = __atomic_load_n(&tail->queue_next, __ATOMIC_ACQUIRE);
        if (tail == (kpl_object*) &object_queue->dummy) {
            if (!queue_next)
                break;
            tail = object_queue->tail = queue_next;
            queue_next = __atomic_load_n(&tail->queue_next, __ATOMIC_ACQUIRE);
        }
        if (!queue_next) {
            kpl_object *head = __atomic_load_n(&object_queue->head, __ATOMIC_ACQUIRE);
            if (head != tail)
                continue;
            kpl_object_queue_enqueue(object_queue, (kpl_object*) &object_queue->dummy);
            queue_next = __atomic_load_n(&tail->queue_next, __ATOMIC_ACQUIRE);
        }
        if (queue_next) {
            object_queue->tail = queue_next;
            object = tail;
            break;
        }
    }
    if (object)
        __atomic_store_n(&object->queue_next, NULL, __ATOMIC_RELAXED);
    return object;
}