module hunt.security.util.ReferenceQueue;
/**
 * Reference queues, to which registered reference objects are appended by the
 * garbage collector after the appropriate reachability changes are detected.
 *
 * @author   Mark Reinhold
 */

class ReferenceQueue(T) {
    // TODO: Tasks pending completion -@zxp at 8/10/2018, 4:15:28 PM
    // 
    /**
     * Constructs a new reference-object queue.
     */
    this() {
    }

    // private static class Null<S> extends ReferenceQueue<S> {
    //     bool enqueue(Reference<S> r) {
    //         return false;
    //     }
    // }

    // static ReferenceQueue<Object> NULL = new Null<>();
    // static ReferenceQueue<Object> ENQUEUED = new Null<>();

    // static private class Lock { };
    // private Lock lock = new Lock();
    // private Reference<T> head = null;
    // private long queueLength = 0;

    // bool enqueue(Reference<T> r) { /* Called only by Reference class */
    //     synchronized (lock) {
    //         // Check that since getting the lock this reference hasn't already been
    //         // enqueued (and even then removed)
    //         ReferenceQueue<?> queue = r.queue;
    //         if ((queue == NULL) || (queue == ENQUEUED)) {
    //             return false;
    //         }
    //         assert queue == this;
    //         r.queue = ENQUEUED;
    //         r.next = (head is null) ? r : head;
    //         head = r;
    //         queueLength++;
    //         if (r instanceof FinalReference) {
    //             sun.misc.VM.addFinalRefCount(1);
    //         }
    //         lock.notifyAll();
    //         return true;
    //     }
    // }

    // @SuppressWarnings("unchecked")
    // private Reference<T> reallyPoll() {       /* Must hold lock */
    //     Reference<T> r = head;
    //     if (r !is null) {
    //         head = (r.next == r) ?
    //             null :
    //             r.next; // Unchecked due to the next field having a raw type in Reference
    //         r.queue = NULL;
    //         r.next = r;
    //         queueLength--;
    //         if (r instanceof FinalReference) {
    //             sun.misc.VM.addFinalRefCount(-1);
    //         }
    //         return r;
    //     }
    //     return null;
    // }

    // /**
    //  * Polls this queue to see if a reference object is available.  If one is
    //  * available without further delay then it is removed from the queue and
    //  * returned.  Otherwise this method immediately returns <tt>null</tt>.
    //  *
    //  * @return  A reference object, if one was immediately available,
    //  *          otherwise <code>null</code>
    //  */
    // Reference<T> poll() {
    //     if (head is null)
    //         return null;
    //     synchronized (lock) {
    //         return reallyPoll();
    //     }
    // }

    // /**
    //  * Removes the next reference object in this queue, blocking until either
    //  * one becomes available or the given timeout period expires.
    //  *
    //  * <p> This method does not offer real-time guarantees: It schedules the
    //  * timeout as if by invoking the {@link Object#wait(long)} method.
    //  *
    //  * @param  timeout  If positive, block for up to <code>timeout</code>
    //  *                  milliseconds while waiting for a reference to be
    //  *                  added to this queue.  If zero, block indefinitely.
    //  *
    //  * @return  A reference object, if one was available within the specified
    //  *          timeout period, otherwise <code>null</code>
    //  *
    //  * @throws  IllegalArgumentException
    //  *          If the value of the timeout argument is negative
    //  *
    //  * @throws  InterruptedException
    //  *          If the timeout wait is interrupted
    //  */
    // Reference<T> remove(long timeout)
    //     throws IllegalArgumentException, InterruptedException
    // {
    //     if (timeout < 0) {
    //         throw new IllegalArgumentException("Negative timeout value");
    //     }
    //     synchronized (lock) {
    //         Reference<T> r = reallyPoll();
    //         if (r !is null) return r;
    //         long start = (timeout == 0) ? 0 : System.nanoTime();
    //         for (;;) {
    //             lock.wait(timeout);
    //             r = reallyPoll();
    //             if (r !is null) return r;
    //             if (timeout != 0) {
    //                 long end = System.nanoTime();
    //                 timeout -= (end - start) / 1000_000;
    //                 if (timeout <= 0) return null;
    //                 start = end;
    //             }
    //         }
    //     }
    // }

    // /**
    //  * Removes the next reference object in this queue, blocking until one
    //  * becomes available.
    //  *
    //  * @return A reference object, blocking until one becomes available
    //  * @throws  InterruptedException  If the wait is interrupted
    //  */
    // Reference<T> remove() throws InterruptedException {
    //     return remove(0);
    // }

}