/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package io.netty.util.internal;

import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

abstract class MpscLinkedQueueTailRef<E> extends MpscLinkedQueuePad1<E> {

    private static final long serialVersionUID = 8717072462993327429L;

    @SuppressWarnings("rawtypes")
    private static final AtomicReferenceFieldUpdater<MpscLinkedQueueTailRef, MpscLinkedQueueNode> UPDATER;

    static {
        @SuppressWarnings("rawtypes")
        AtomicReferenceFieldUpdater<MpscLinkedQueueTailRef, MpscLinkedQueueNode> updater;
        updater = PlatformDependent.newAtomicReferenceFieldUpdater(MpscLinkedQueueTailRef.class, "tailRef");
        if (updater == null) {
            updater = AtomicReferenceFieldUpdater.newUpdater(
                    MpscLinkedQueueTailRef.class, MpscLinkedQueueNode.class, "tailRef");
        }
        UPDATER = updater;
    }

    private transient volatile MpscLinkedQueueNode<E> tailRef;

    protected final MpscLinkedQueueNode<E> tailRef() {
        return tailRef;
    }

    protected final void setTailRef(MpscLinkedQueueNode<E> tailRef) {
        this.tailRef = tailRef;
    }

    @SuppressWarnings("unchecked")
    protected final MpscLinkedQueueNode<E> getAndSetTailRef(MpscLinkedQueueNode<E> tailRef) {
        // LOCK XCHG in JDK8, a CAS loop in JDK 7/6
        return (MpscLinkedQueueNode<E>) UPDATER.getAndSet(this, tailRef);
    }
}