/**
 * Creates a new instance
 *
 * @param sslCtx an OpenSSL {@code SSL_CTX} object
 * @param alloc the {@link ByteBufAllocator} that will be used by this engine
 * @param clientMode {@code true} if this is used for clients, {@code false} otherwise
 * @param sessionContext the {@link OpenSslSessionContext} this {@link SSLEngine} belongs to.
 */
OpenSslEngine(long sslCtx, ByteBufAllocator alloc, String fallbackApplicationProtocol,
              boolean clientMode, OpenSslSessionContext sessionContext, OpenSslEngineMap engineMap) {
    OpenSsl.ensureAvailability();
    if (sslCtx == 0) {
        throw new NullPointerException("sslCtx");
    }

    this.alloc = ObjectUtil.checkNotNull(alloc, "alloc");
    ssl = SSL.newSSL(sslCtx, !clientMode);
    networkBIO = SSL.makeNetworkBIO(ssl);
    this.fallbackApplicationProtocol = fallbackApplicationProtocol;
    this.clientMode = clientMode;
    this.sessionContext = sessionContext;
    this.engineMap = engineMap;
}
 

@Override
public void putValue(String name, Object value) {
    ObjectUtil.checkNotNull(name, "name");
    ObjectUtil.checkNotNull(value, "value");

    Map<String, Object> values = this.values;
    if (values == null) {
        // Use size of 2 to keep the memory overhead small
        values = this.values = new HashMap<String, Object>(2);
    }
    Object old = values.put(name, value);
    if (value instanceof SSLSessionBindingListener) {
        ((SSLSessionBindingListener) value).valueBound(new SSLSessionBindingEvent(this, name));
    }
    notifyUnbound(old, name);
}
 

public static String removeSlashesAtBothEnds(String path) {
    ObjectUtil.checkNotNull(path, "path");

    if (path.isEmpty()) {
        return path;
    }

    int beginIndex = 0;
    while (beginIndex < path.length() && path.charAt(beginIndex) == '/') {
        beginIndex++;
    }
    if (beginIndex == path.length()) {
        return "";
    }

    int endIndex = path.length() - 1;
    while (endIndex > beginIndex && path.charAt(endIndex) == '/') {
        endIndex--;
    }

    return path.substring(beginIndex, endIndex + 1);
}
 

/**
 * Sets the SSL session ticket keys of this context.设置此上下文的SSL会话票据密钥。
 */
public void setTicketKeys(OpenSslSessionTicketKey... keys) {
    ObjectUtil.checkNotNull(keys, "keys");
    SessionTicketKey[] ticketKeys = new SessionTicketKey[keys.length];
    for (int i = 0; i < ticketKeys.length; i++) {
        ticketKeys[i] = keys[i].key;
    }
    Lock writerLock = context.ctxLock.writeLock();
    writerLock.lock();
    try {
        SSLContext.clearOptions(context.ctx, SSL.SSL_OP_NO_TICKET);
        SSLContext.setSessionTicketKeys(context.ctx, ticketKeys);
    } finally {
        writerLock.unlock();
    }
}
 

@Override
public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
    ObjectUtil.checkNotNull(command, "command");
    ObjectUtil.checkNotNull(unit, "unit");
    if (initialDelay < 0) {
        throw new IllegalArgumentException(
                String.format("initialDelay: %d (expected: >= 0)", initialDelay));
    }
    if (period <= 0) {
        throw new IllegalArgumentException(
                String.format("period: %d (expected: > 0)", period));
    }

    return schedule(new ScheduledFutureTask<Void>(
            this, Executors.<Void>callable(command, null),
            ScheduledFutureTask.deadlineNanos(unit.toNanos(initialDelay)), unit.toNanos(period)));
}
 

static void invokeExceptionCaught(final AbstractChannelHandlerContext next, final Throwable cause) {
    ObjectUtil.checkNotNull(cause, "cause");
    EventExecutor executor = next.executor();
    if (executor.inEventLoop()) {
        next.invokeExceptionCaught(cause);
    } else {
        try {
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    next.invokeExceptionCaught(cause);
                }
            });
        } catch (Throwable t) {
            if (logger.isWarnEnabled()) {
                logger.warn("Failed to submit an exceptionCaught() event.", t);
                logger.warn("The exceptionCaught() event that was failed to submit was:", cause);
            }
        }
    }
}
 

/**
 * Adds a task to be run once at the end of next (or current) {@code eventloop} iteration.
 *
 * @param task to be added.
 *             在下一次(或当前)eventloop迭代结束时添加一个要运行一次的任务。
 */
@UnstableApi
public final void executeAfterEventLoopIteration(Runnable task) {
    ObjectUtil.checkNotNull(task, "task");
    if (isShutdown()) {
        reject();
    }

    if (!tailTasks.offer(task)) {
        reject(task);
    }

    if (wakesUpForTask(task)) {
        wakeup(inEventLoop());
    }
}
 

/**
 * Creates a new instance.
 *
 * @param byteOrder         the {@link ByteOrder} of the length field
 * @param lengthFieldLength the length of the prepended length field.
 *                          Only 1, 2, 3, 4, and 8 are allowed.
 * @param lengthAdjustment  the compensation value to add to the value
 *                          of the length field
 * @param lengthIncludesLengthFieldLength
 *                          if {@code true}, the length of the prepended
 *                          length field is added to the value of the
 *                          prepended length field.
 *
 * @throws IllegalArgumentException
 *         if {@code lengthFieldLength} is not 1, 2, 3, 4, or 8
 */
public LengthFieldPrepender(
        ByteOrder byteOrder, int lengthFieldLength,
        int lengthAdjustment, boolean lengthIncludesLengthFieldLength) {
    if (lengthFieldLength != 1 && lengthFieldLength != 2 &&
        lengthFieldLength != 3 && lengthFieldLength != 4 &&
        lengthFieldLength != 8) {
        throw new IllegalArgumentException(
                "lengthFieldLength must be either 1, 2, 3, 4, or 8: " +
                lengthFieldLength);
    }
    ObjectUtil.checkNotNull(byteOrder, "byteOrder");

    this.byteOrder = byteOrder;
    this.lengthFieldLength = lengthFieldLength;
    this.lengthIncludesLengthFieldLength = lengthIncludesLengthFieldLength;
    this.lengthAdjustment = lengthAdjustment;
}
 

/**
     * Creates a new customizable LZ4 encoder.创建一个新的可定制的LZ4编码器。
     *
     * @param factory         user customizable {@link LZ4Factory} instance
     *                        which may be JNI bindings to the original C implementation, a pure Java implementation
     *                        or a Java implementation that uses the {@link sun.misc.Unsafe}
     * @param highCompressor  if {@code true} codec will use compressor which requires more memory
     *                        and is slower but compresses more efficiently
     * @param blockSize       the maximum number of bytes to try to compress at once,
     *                        must be >= 64 and <= 32 M
     * @param checksum        the {@link Checksum} instance to use to check data for integrity
     * @param maxEncodeSize   the maximum size for an encode (compressed) buffer
     */
public Lz4FrameEncoder(LZ4Factory factory, boolean highCompressor, int blockSize,
                       Checksum checksum, int maxEncodeSize) {
    if (factory == null) {
        throw new NullPointerException("factory");
    }
    if (checksum == null) {
        throw new NullPointerException("checksum");
    }

    compressor = highCompressor ? factory.highCompressor() : factory.fastCompressor();
    this.checksum = ByteBufChecksum.wrapChecksum(checksum);

    compressionLevel = compressionLevel(blockSize);
    this.blockSize = blockSize;
    this.maxEncodeSize = ObjectUtil.checkPositive(maxEncodeSize, "maxEncodeSize");
    finished = false;
}
 

@Override
public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
    ObjectUtil.checkNotNull(command, "command");
    ObjectUtil.checkNotNull(unit, "unit");
    if (initialDelay < 0) {
        throw new IllegalArgumentException(
                String.format("initialDelay: %d (expected: >= 0)", initialDelay));
    }
    if (period <= 0) {
        throw new IllegalArgumentException(
                String.format("period: %d (expected: > 0)", period));
    }

    return schedule(new ScheduledFutureTask<Void>(
            this, Executors.<Void>callable(command, null),
            ScheduledFutureTask.deadlineNanos(unit.toNanos(initialDelay)), unit.toNanos(period)));
}
 

@Override
public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
    ObjectUtil.checkNotNull(command, "command");
    ObjectUtil.checkNotNull(unit, "unit");
    if (initialDelay < 0) {
        throw new IllegalArgumentException(
                String.format("initialDelay: %d (expected: >= 0)", initialDelay));
    }
    if (delay <= 0) {
        throw new IllegalArgumentException(
                String.format("delay: %d (expected: > 0)", delay));
    }

    return schedule(new ScheduledFutureTask<Void>(
            this, Executors.<Void>callable(command, null),
            ScheduledFutureTask.deadlineNanos(unit.toNanos(initialDelay)), -unit.toNanos(delay)));
}
 

/**
 * Tries to backoff when the task can not be added due restrictions for an configured amount of time. This
 * is only done if the task was added from outside of the event loop which means
 * {@link EventExecutor#inEventLoop()} returns {@code false}.
 * 尝试在任务无法被添加时进行回退，这是对已配置的时间的适当限制。这只在从事件循环外部添加任务时完成，这意味着EventExecutor.inEventLoop()返回false。
 */
public static RejectedExecutionHandler backoff(final int retries, long backoffAmount, TimeUnit unit) {
    ObjectUtil.checkPositive(retries, "retries");
    final long backOffNanos = unit.toNanos(backoffAmount);
    return new RejectedExecutionHandler() {
        @Override
        public void rejected(Runnable task, SingleThreadEventExecutor executor) {
            if (!executor.inEventLoop()) {
                for (int i = 0; i < retries; i++) {
                    // Try to wake up the executor so it will empty its task queue.
                    executor.wakeup(false);

                    LockSupport.parkNanos(backOffNanos);
                    if (executor.offerTask(task)) {
                        return;
                    }
                }
            }
            // Either we tried to add the task from within the EventLoop or we was not able to add it even with
            // backoff.
            throw new RejectedExecutionException();
        }
    };
}
 

/**
 * Creates a new instance.
 *
 * @param byteOrder         the {@link ByteOrder} of the length field
 * @param lengthFieldLength the length of the prepended length field.
 *                          Only 1, 2, 3, 4, and 8 are allowed.
 * @param lengthAdjustment  the compensation value to add to the value
 *                          of the length field
 * @param lengthIncludesLengthFieldLength
 *                          if {@code true}, the length of the prepended
 *                          length field is added to the value of the
 *                          prepended length field.
 *
 * @throws IllegalArgumentException
 *         if {@code lengthFieldLength} is not 1, 2, 3, 4, or 8
 */
public LengthFieldPrepender(
        ByteOrder byteOrder, int lengthFieldLength,
        int lengthAdjustment, boolean lengthIncludesLengthFieldLength) {
    if (lengthFieldLength != 1 && lengthFieldLength != 2 &&
        lengthFieldLength != 3 && lengthFieldLength != 4 &&
        lengthFieldLength != 8) {
        throw new IllegalArgumentException(
                "lengthFieldLength must be either 1, 2, 3, 4, or 8: " +
                lengthFieldLength);
    }
    ObjectUtil.checkNotNull(byteOrder, "byteOrder");

    this.byteOrder = byteOrder;
    this.lengthFieldLength = lengthFieldLength;
    this.lengthIncludesLengthFieldLength = lengthIncludesLengthFieldLength;
    this.lengthAdjustment = lengthAdjustment;
}
 

/**
 * The maps will be wrapped in Collections.unmodifiableMap.
 */
public RouteResult(String uri, String decodedPath, Map<String, String> pathParams, Map<String, List<String>> queryParams, T target) {
	this.uri = ObjectUtil.checkNotNull(uri, "uri");
	this.decodedPath = ObjectUtil.checkNotNull(decodedPath, "decodedPath");
	this.pathParams = Collections.unmodifiableMap(ObjectUtil.checkNotNull(pathParams, "pathParams"));
	this.queryParams = Collections.unmodifiableMap(ObjectUtil.checkNotNull(queryParams, "queryParams"));
	this.target = ObjectUtil.checkNotNull(target, "target");
}
 

@Override
public void setEnabledCipherSuites(String[] cipherSuites) {
    ObjectUtil.checkNotNull(cipherSuites, "cipherSuites");

    final StringBuilder buf = new StringBuilder();
    for (String c: cipherSuites) {
        if (c == null) {
            break;
        }

        String converted = CipherSuiteConverter.toOpenSsl(c);
        if (converted == null) {
            converted = c;
        }

        if (!OpenSsl.isCipherSuiteAvailable(converted)) {
            throw new IllegalArgumentException("unsupported cipher suite: " + c + '(' + converted + ')');
        }

        buf.append(converted);
        buf.append(':');
    }

    if (buf.length() == 0) {
        throw new IllegalArgumentException("empty cipher suites");
    }
    buf.setLength(buf.length() - 1);

    final String cipherSuiteSpec = buf.toString();
    try {
        SSL.setCipherSuites(ssl, cipherSuiteSpec);
    } catch (Exception e) {
        throw new IllegalStateException("failed to enable cipher suites: " + cipherSuiteSpec, e);
    }
}
 

/**
 * The pattern must not contain query, example:
 * {@code constant1/constant2?foo=bar}.
 *
 * <p>The pattern will be stored without slashes at both ends.
 */
public PathPattern(String pattern) {
	if (pattern.contains("?")) {
		throw new IllegalArgumentException("Path pattern must not contain query");
	}

	this.pattern = removeSlashesAtBothEnds(ObjectUtil.checkNotNull(pattern, "pattern"));
	this.tokens = this.pattern.split("/");
}
 

/**
 * The pattern must not contain query, example:
 * {@code constant1/constant2?foo=bar}.
 *
 * <p>The pattern will be stored without slashes at both ends.
 */
public PathPattern(String pattern) {
    if (pattern.contains("?")) {
        throw new IllegalArgumentException("Path pattern must not contain query");
    }

    this.pattern = removeSlashesAtBothEnds(ObjectUtil.checkNotNull(pattern, "pattern"));
    this.tokens = this.pattern.split("/");
}
 

@Override
public void removeValue(String name) {
    ObjectUtil.checkNotNull(name, "name");

    Map<String, Object> values = this.values;
    if (values == null) {
        return;
    }
    Object old = values.remove(name);
    notifyUnbound(old, name);
}
 

/**
 * The pattern must not contain query, example:
 * {@code constant1/constant2?foo=bar}.
 *
 * <p>The pattern will be stored without slashes at both ends.
 */
public PathPattern(String pattern) {
    if (pattern.contains("?")) {
        throw new IllegalArgumentException("Path pattern must not contain query");
    }

    this.pattern = removeSlashesAtBothEnds(ObjectUtil.checkNotNull(pattern, "pattern"));
    this.tokens = this.pattern.split("/");
}
 

/**
 * Adds a parameter with the specified name and value to this encoder.向此编码器添加具有指定名称和值的参数。
 */
public void addParam(String name, String value) {
    ObjectUtil.checkNotNull(name, "name");
    if (hasParams) {
        uriBuilder.append('&');
    } else {
        uriBuilder.append('?');
        hasParams = true;
    }
    appendComponent(name, charsetName, uriBuilder);
    if (value != null) {
        uriBuilder.append('=');
        appendComponent(value, charsetName, uriBuilder);
    }
}
 

public MqttFixedHeader(
        MqttMessageType messageType,
        boolean isDup,
        MqttQoS qosLevel,
        boolean isRetain,
        int remainingLength) {
    this.messageType = ObjectUtil.checkNotNull(messageType, "messageType");
    this.isDup = isDup;
    this.qosLevel = ObjectUtil.checkNotNull(qosLevel, "qosLevel");
    this.isRetain = isRetain;
    this.remainingLength = remainingLength;
}
 

DnsNameResolverContext(DnsNameResolver parent,
                       String hostname,
                       DnsRecord[] additionals,
                       DnsCache resolveCache,
                       DnsServerAddressStream nameServerAddrs) {
    this.parent = parent;
    this.hostname = hostname;
    this.additionals = additionals;
    this.resolveCache = resolveCache;

    this.nameServerAddrs = ObjectUtil.checkNotNull(nameServerAddrs, "nameServerAddrs");
    maxAllowedQueries = parent.maxQueriesPerResolve();
    resolvedInternetProtocolFamilies = parent.resolvedInternetProtocolFamiliesUnsafe();
    allowedQueries = maxAllowedQueries;
}
 

/**
 * Set the specific {@link AttributeKey} with the given value on every child {@link Channel}. If the value is
 * {@code null} the {@link AttributeKey} is removed
 */
public <T> UkcpServerBootstrap childAttr(AttributeKey<T> childKey, T value) {
    ObjectUtil.checkNotNull(childKey, "childKey");
    if (value == null) {
        childAttrs.remove(childKey);
    } else {
        childAttrs.put(childKey, value);
    }
    return this;
}
 

public ZstdEncoder(int blockSize, int maxEncodeSize) {
    super(true);
    compressionLevel = compressionLevel(blockSize);
    this.blockSize = blockSize;
    this.maxEncodeSize = ObjectUtil.checkPositive(maxEncodeSize, "maxEncodeSize");
    finished = false;
}
 

@Override
public  ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
    ObjectUtil.checkNotNull(command, "command");
    ObjectUtil.checkNotNull(unit, "unit");
    if (delay < 0) {
        throw new IllegalArgumentException(
                String.format("delay: %d (expected: >= 0)", delay));
    }
    return schedule(new ScheduledFutureTask<Void>(
            this, command, null, ScheduledFutureTask.deadlineNanos(unit.toNanos(delay))));
}
 

AbstractChannelHandlerContext(DefaultChannelPipeline pipeline, EventExecutor executor, String name,
                              boolean inbound, boolean outbound) {
    this.name = ObjectUtil.checkNotNull(name, "name");
    this.pipeline = pipeline;
    this.executor = executor;
    this.inbound = inbound;
    this.outbound = outbound;
    // Its ordered if its driven by the EventLoop or the given Executor is an instanceof OrderedEventExecutor.
    ordered = executor == null || executor instanceof OrderedEventExecutor;
}
 

static void invokeUserEventTriggered(final AbstractChannelHandlerContext next, final Object event) {
    ObjectUtil.checkNotNull(event, "event");
    EventExecutor executor = next.executor();
    if (executor.inEventLoop()) {
        next.invokeUserEventTriggered(event);
    } else {
        executor.execute(new Runnable() {
            @Override
            public void run() {
                next.invokeUserEventTriggered(event);
            }
        });
    }
}
 

static void invokeChannelRead(final AbstractChannelHandlerContext next, Object msg) {
    final Object m = next.pipeline.touch(ObjectUtil.checkNotNull(msg, "msg"), next);
    EventExecutor executor = next.executor();
    if (executor.inEventLoop()) {
        next.invokeChannelRead(m);
    } else {
        executor.execute(new Runnable() {
            @Override
            public void run() {
                next.invokeChannelRead(m);
            }
        });
    }
}
 

protected DefaultChannelPipeline(Channel channel) {
    this.channel = ObjectUtil.checkNotNull(channel, "channel");
    succeededFuture = new SucceededChannelFuture(channel, null);
    voidPromise =  new VoidChannelPromise(channel, true);

    tail = new TailContext(this);
    head = new HeadContext(this);

    head.next = tail;
    tail.prev = head;
}
 

@Override
public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
    ObjectUtil.checkNotNull(callable, "callable");
    ObjectUtil.checkNotNull(unit, "unit");
    if (delay < 0) {
        throw new IllegalArgumentException(
                String.format("delay: %d (expected: >= 0)", delay));
    }
    return schedule(new ScheduledFutureTask<V>(
            this, callable, ScheduledFutureTask.deadlineNanos(unit.toNanos(delay))));
}