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package shz.core.node;

import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

/**
 * 元素类型为long支持并发的单向链表节点
 * 
 * 16*n(n为元素个数)
 * 
 * B=16*(n+1)
 */
@SuppressWarnings("restriction")
public class ConcurrentJSNode implements SNode {
    private static final long serialVersionUID = -6374622330255464371L;
    public volatile long val;
    protected volatile ConcurrentJSNode next;

    protected ConcurrentJSNode(long val) {
        this.val = val;
    }

    public static ConcurrentJSNode of(long e) {
        return new ConcurrentJSNode(e);
    }

    public static ConcurrentJSNode of() {
        return of(0L);
    }

    private static final AtomicLongFieldUpdater valUpdater = AtomicLongFieldUpdater.newUpdater(ConcurrentJSNode.class, "val");
    private static final AtomicReferenceFieldUpdater nextUpdater = AtomicReferenceFieldUpdater.newUpdater(ConcurrentJSNode.class, ConcurrentJSNode.class, "next");

    public final boolean casVal(long expect, long update) {
        return valUpdater.compareAndSet(this, expect, update);
    }

    public final boolean casNext(ConcurrentJSNode expect, ConcurrentJSNode update) {
        return nextUpdater.compareAndSet(this, expect, update);
    }

    @Override
    public final ConcurrentJSNode next() {
        return next;
    }

    @Override
    public final void next(ConcurrentJSNode node) {
        next = node;
    }

    @Override
    public final ConcurrentJSNode addNext(ConcurrentJSNode node) {
        ConcurrentJSNode next;
        do {
            next = this.next;
            node.next = next;
        } while (!casNext(next, node));
        return node;
    }

    @Override
    public final ConcurrentJSNode addPrev(ConcurrentJSNode node) {
        ConcurrentJSNode cjsNode = addNext(node);
        long val;
        do {
            val = this.val;
        } while (!casVal(val, cjsNode.val));
        cjsNode.val = val;
        return this;
    }

    @Override
    public final void poll() {
        if (next == null) this.val = 0L;
        else {
            ConcurrentJSNode next = this.next;
            if (casNext(next, next.next)) this.val = next.val;
        }
    }

    public final ConcurrentJSNode addNext(long e) {
        return addNext(of(e));
    }

    public final ConcurrentJSNode addNext(long... es) {
        ConcurrentJSNode next = this;
        for (long e : es) next = next.addNext(e);
        return next;
    }

    public final ConcurrentJSNode addPrev(long e) {
        return addPrev(of(e));
    }

    public final ConcurrentJSNode addPrev(long... es) {
        for (long e : es) addPrev(e);
        return this;
    }
}