Chase-lev双端队列中的原子存储

Chase-Lev双端队列是一种无锁的并发数据结构，用于多线程环境下的双端队列操作。它使用原子操作来保证并发安全性。

以下是一个使用Java语言实现Chase-Lev双端队列的示例代码：

import java.util.concurrent.atomic.AtomicReference;

public class ChaseLevDeque<T> {
    private static class Node<T> {
        T value;
        AtomicReference<Node<T>> next;

        Node(T value) {
            this.value = value;
            this.next = new AtomicReference<>(null);
        }
    }

    private AtomicReference<Node<T>> head;
    private AtomicReference<Node<T>> tail;

    public ChaseLevDeque() {
        Node<T> dummyNode = new Node<>(null);
        this.head = new AtomicReference<>(dummyNode);
        this.tail = new AtomicReference<>(dummyNode);
    }

    public void enqueueHead(T value) {
        Node<T> newNode = new Node<>(value);
        Node<T> oldHead;
        do {
            oldHead = head.get();
            newNode.next.set(oldHead);
        } while (!head.compareAndSet(oldHead, newNode));
    }

    public void enqueueTail(T value) {
        Node<T> newNode = new Node<>(value);
        Node<T> oldTail;
        Node<T> oldTailNext;
        do {
            oldTail = tail.get();
            oldTailNext = oldTail.next.get();
            if (oldTailNext != null) {
                tail.compareAndSet(oldTail, oldTailNext);
            }
        } while (!oldTail.next.compareAndSet(null, newNode));
        tail.compareAndSet(oldTail, newNode);
    }

    public T dequeueHead() {
        Node<T> oldHead;
        Node<T> oldTail;
        Node<T> newHead;
        do {
            oldHead = head.get();
            oldTail = tail.get();
            newHead = oldHead.next.get();
            if (oldHead == head.get()) {
                if (oldHead == oldTail) {
                    if (newHead == null) {
                        return null;
                    }
                    tail.compareAndSet(oldTail, newHead);
                } else {
                    T value = newHead.value;
                    if (head.compareAndSet(oldHead, newHead)) {
                        return value;
                    }
                }
            }
        } while (true);
    }

    public T dequeueTail() {
        Node<T> oldHead;
        Node<T> oldTail;
        Node<T> newHead;
        do {
            oldHead = head.get();
            oldTail = tail.get();
            newHead = oldHead.next.get();
            if (oldHead == head.get()) {
                if (oldHead == oldTail) {
                    if (newHead == null) {
                        return null;
                    }
                    tail.compareAndSet(oldTail, newHead);
                } else {
                    Node<T> curr = newHead;
                    Node<T> prev = oldHead;
                    while (curr.next.get() != null) {
                        prev = curr;
                        curr = curr.next.get();
                    }
                    T value = curr.value;
                    if (prev.next.compareAndSet(curr, null)) {
                        return value;
                    }
                }
            }
        } while (true);
    }
}

在上述代码中，ChaseLevDeque类使用AtomicReference来保存头节点和尾节点。enqueueHead方法通过CAS（Compare and Swap）操作将新节点插入到头部。enqueueTail方法则使用CAS操作将新节点插入到尾部。dequeueHead和dequeueTail方法则通过自旋操作来取出队列中的头部和尾部节点，并更新头结点和尾节点。

该实现中使用了原子操作来保证并发安全性，确保多线程环境下的双端队列操作的正确性。