Netty ChannelPipeline 中的addFirst和addLast实现

在DefaultChannelPipeline中使用双向链表实现addFirst和addLast逻辑

final class DefaultChannelPipeline implements ChannelPipeline {    static final InternalLogger logger = InternalLoggerFactory.getInstance(DefaultChannelPipeline.class);    @SuppressWarnings("unchecked")    private static final WeakHashMap<Class<?>, String>[] nameCaches =            new WeakHashMap[Runtime.getRuntime().availableProcessors()];    static {        for (int i = 0; i < nameCaches.length; i ++) {            nameCaches[i] = new WeakHashMap<Class<?>, String>();        }    }    final AbstractChannel channel;    final AbstractChannelHandlerContext head;    final AbstractChannelHandlerContext tail;    private final Map<String, AbstractChannelHandlerContext> name2ctx =        new HashMap<String, AbstractChannelHandlerContext>(4);

。。。。

}

可以看到AbstractChannelHandlerContext head和tail

进入看AbstractChannelHandlerContext ：

abstract class AbstractChannelHandlerContext extends DefaultAttributeMap implements ChannelHandlerContext {    volatile AbstractChannelHandlerContext next;    volatile AbstractChannelHandlerContext prev;    private final boolean inbound;    private final boolean outbound;    private final AbstractChannel channel;    private final DefaultChannelPipeline pipeline;    private final String name;

。。。。}

可以看到是双向链表结构，并有ChannelHandler的类型标示：boolean inbound, outbound

具体看addFirst和addLast方法源码：

在addFirst中最终调用了addFirst0方法：

private void addFirst0(String name, AbstractChannelHandlerContext newCtx) {    checkMultiplicity(newCtx);    AbstractChannelHandlerContext nextCtx = head.next;    newCtx.prev = head;    newCtx.next = nextCtx;    head.next = newCtx;    nextCtx.prev = newCtx;    name2ctx.put(name, newCtx);    callHandlerAdded(newCtx);}

在addLast中最终调用了addLast0方法：

private void addLast0(final String name, AbstractChannelHandlerContext newCtx) {    checkMultiplicity(newCtx);    AbstractChannelHandlerContext prev = tail.prev;    newCtx.prev = prev;    newCtx.next = tail;    prev.next = newCtx;    tail.prev = newCtx;    name2ctx.put(name, newCtx);    callHandlerAdded(newCtx);}