| /* |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /* |
| * This file is available under and governed by the GNU General Public |
| * License version 2 only, as published by the Free Software Foundation. |
| * However, the following notice accompanied the original version of this |
| * file: |
| * |
| * Written by Doug Lea with assistance from members of JCP JSR-166 |
| * Expert Group and released to the public domain, as explained at |
| * http://creativecommons.org/publicdomain/zero/1.0/ |
| */ |
| |
| package java.util.concurrent; |
| |
| import java.lang.invoke.MethodHandles; |
| import java.lang.invoke.VarHandle; |
| import java.util.ArrayList; |
| import java.util.List; |
| import java.util.concurrent.locks.LockSupport; |
| import java.util.function.BiConsumer; |
| import java.util.function.BiPredicate; |
| import java.util.function.Consumer; |
| |
| /** |
| * A {@link Flow.Publisher} that asynchronously issues submitted |
| * (non-null) items to current subscribers until it is closed. Each |
| * current subscriber receives newly submitted items in the same order |
| * unless drops or exceptions are encountered. Using a |
| * SubmissionPublisher allows item generators to act as compliant <a |
| * href="http://www.reactive-streams.org/"> reactive-streams</a> |
| * Publishers relying on drop handling and/or blocking for flow |
| * control. |
| * |
| * <p>A SubmissionPublisher uses the {@link Executor} supplied in its |
| * constructor for delivery to subscribers. The best choice of |
| * Executor depends on expected usage. If the generator(s) of |
| * submitted items run in separate threads, and the number of |
| * subscribers can be estimated, consider using a {@link |
| * Executors#newFixedThreadPool}. Otherwise consider using the |
| * default, normally the {@link ForkJoinPool#commonPool}. |
| * |
| * <p>Buffering allows producers and consumers to transiently operate |
| * at different rates. Each subscriber uses an independent buffer. |
| * Buffers are created upon first use and expanded as needed up to the |
| * given maximum. (The enforced capacity may be rounded up to the |
| * nearest power of two and/or bounded by the largest value supported |
| * by this implementation.) Invocations of {@link |
| * Flow.Subscription#request(long) request} do not directly result in |
| * buffer expansion, but risk saturation if unfilled requests exceed |
| * the maximum capacity. The default value of {@link |
| * Flow#defaultBufferSize()} may provide a useful starting point for |
| * choosing a capacity based on expected rates, resources, and usages. |
| * |
| * <p>Publication methods support different policies about what to do |
| * when buffers are saturated. Method {@link #submit(Object) submit} |
| * blocks until resources are available. This is simplest, but least |
| * responsive. The {@code offer} methods may drop items (either |
| * immediately or with bounded timeout), but provide an opportunity to |
| * interpose a handler and then retry. |
| * |
| * <p>If any Subscriber method throws an exception, its subscription |
| * is cancelled. If a handler is supplied as a constructor argument, |
| * it is invoked before cancellation upon an exception in method |
| * {@link Flow.Subscriber#onNext onNext}, but exceptions in methods |
| * {@link Flow.Subscriber#onSubscribe onSubscribe}, |
| * {@link Flow.Subscriber#onError(Throwable) onError} and |
| * {@link Flow.Subscriber#onComplete() onComplete} are not recorded or |
| * handled before cancellation. If the supplied Executor throws |
| * {@link RejectedExecutionException} (or any other RuntimeException |
| * or Error) when attempting to execute a task, or a drop handler |
| * throws an exception when processing a dropped item, then the |
| * exception is rethrown. In these cases, not all subscribers will |
| * have been issued the published item. It is usually good practice to |
| * {@link #closeExceptionally closeExceptionally} in these cases. |
| * |
| * <p>Method {@link #consume(Consumer)} simplifies support for a |
| * common case in which the only action of a subscriber is to request |
| * and process all items using a supplied function. |
| * |
| * <p>This class may also serve as a convenient base for subclasses |
| * that generate items, and use the methods in this class to publish |
| * them. For example here is a class that periodically publishes the |
| * items generated from a supplier. (In practice you might add methods |
| * to independently start and stop generation, to share Executors |
| * among publishers, and so on, or use a SubmissionPublisher as a |
| * component rather than a superclass.) |
| * |
| * <pre> {@code |
| * class PeriodicPublisher<T> extends SubmissionPublisher<T> { |
| * final ScheduledFuture<?> periodicTask; |
| * final ScheduledExecutorService scheduler; |
| * PeriodicPublisher(Executor executor, int maxBufferCapacity, |
| * Supplier<? extends T> supplier, |
| * long period, TimeUnit unit) { |
| * super(executor, maxBufferCapacity); |
| * scheduler = new ScheduledThreadPoolExecutor(1); |
| * periodicTask = scheduler.scheduleAtFixedRate( |
| * () -> submit(supplier.get()), 0, period, unit); |
| * } |
| * public void close() { |
| * periodicTask.cancel(false); |
| * scheduler.shutdown(); |
| * super.close(); |
| * } |
| * }}</pre> |
| * |
| * <p>Here is an example of a {@link Flow.Processor} implementation. |
| * It uses single-step requests to its publisher for simplicity of |
| * illustration. A more adaptive version could monitor flow using the |
| * lag estimate returned from {@code submit}, along with other utility |
| * methods. |
| * |
| * <pre> {@code |
| * class TransformProcessor<S,T> extends SubmissionPublisher<T> |
| * implements Flow.Processor<S,T> { |
| * final Function<? super S, ? extends T> function; |
| * Flow.Subscription subscription; |
| * TransformProcessor(Executor executor, int maxBufferCapacity, |
| * Function<? super S, ? extends T> function) { |
| * super(executor, maxBufferCapacity); |
| * this.function = function; |
| * } |
| * public void onSubscribe(Flow.Subscription subscription) { |
| * (this.subscription = subscription).request(1); |
| * } |
| * public void onNext(S item) { |
| * subscription.request(1); |
| * submit(function.apply(item)); |
| * } |
| * public void onError(Throwable ex) { closeExceptionally(ex); } |
| * public void onComplete() { close(); } |
| * }}</pre> |
| * |
| * @param <T> the published item type |
| * @author Doug Lea |
| * @since 9 |
| */ |
| public class SubmissionPublisher<T> implements Flow.Publisher<T>, |
| AutoCloseable { |
| /* |
| * Most mechanics are handled by BufferedSubscription. This class |
| * mainly tracks subscribers and ensures sequentiality, by using |
| * built-in synchronization locks across public methods. (Using |
| * built-in locks works well in the most typical case in which |
| * only one thread submits items). |
| */ |
| |
| /** The largest possible power of two array size. */ |
| static final int BUFFER_CAPACITY_LIMIT = 1 << 30; |
| |
| /** Round capacity to power of 2, at most limit. */ |
| static final int roundCapacity(int cap) { |
| int n = cap - 1; |
| n |= n >>> 1; |
| n |= n >>> 2; |
| n |= n >>> 4; |
| n |= n >>> 8; |
| n |= n >>> 16; |
| return (n <= 0) ? 1 : // at least 1 |
| (n >= BUFFER_CAPACITY_LIMIT) ? BUFFER_CAPACITY_LIMIT : n + 1; |
| } |
| |
| // default Executor setup; nearly the same as CompletableFuture |
| |
| /** |
| * Default executor -- ForkJoinPool.commonPool() unless it cannot |
| * support parallelism. |
| */ |
| private static final Executor ASYNC_POOL = |
| (ForkJoinPool.getCommonPoolParallelism() > 1) ? |
| ForkJoinPool.commonPool() : new ThreadPerTaskExecutor(); |
| |
| /** Fallback if ForkJoinPool.commonPool() cannot support parallelism */ |
| private static final class ThreadPerTaskExecutor implements Executor { |
| ThreadPerTaskExecutor() {} // prevent access constructor creation |
| public void execute(Runnable r) { new Thread(r).start(); } |
| } |
| |
| /** |
| * Clients (BufferedSubscriptions) are maintained in a linked list |
| * (via their "next" fields). This works well for publish loops. |
| * It requires O(n) traversal to check for duplicate subscribers, |
| * but we expect that subscribing is much less common than |
| * publishing. Unsubscribing occurs only during traversal loops, |
| * when BufferedSubscription methods return negative values |
| * signifying that they have been disabled. To reduce |
| * head-of-line blocking, submit and offer methods first call |
| * BufferedSubscription.offer on each subscriber, and place |
| * saturated ones in retries list (using nextRetry field), and |
| * retry, possibly blocking or dropping. |
| */ |
| BufferedSubscription<T> clients; |
| |
| /** Run status, updated only within locks */ |
| volatile boolean closed; |
| /** If non-null, the exception in closeExceptionally */ |
| volatile Throwable closedException; |
| |
| // Parameters for constructing BufferedSubscriptions |
| final Executor executor; |
| final BiConsumer<? super Flow.Subscriber<? super T>, ? super Throwable> onNextHandler; |
| final int maxBufferCapacity; |
| |
| /** |
| * Creates a new SubmissionPublisher using the given Executor for |
| * async delivery to subscribers, with the given maximum buffer size |
| * for each subscriber, and, if non-null, the given handler invoked |
| * when any Subscriber throws an exception in method {@link |
| * Flow.Subscriber#onNext(Object) onNext}. |
| * |
| * @param executor the executor to use for async delivery, |
| * supporting creation of at least one independent thread |
| * @param maxBufferCapacity the maximum capacity for each |
| * subscriber's buffer (the enforced capacity may be rounded up to |
| * the nearest power of two and/or bounded by the largest value |
| * supported by this implementation; method {@link #getMaxBufferCapacity} |
| * returns the actual value) |
| * @param handler if non-null, procedure to invoke upon exception |
| * thrown in method {@code onNext} |
| * @throws NullPointerException if executor is null |
| * @throws IllegalArgumentException if maxBufferCapacity not |
| * positive |
| */ |
| public SubmissionPublisher(Executor executor, int maxBufferCapacity, |
| BiConsumer<? super Flow.Subscriber<? super T>, ? super Throwable> handler) { |
| if (executor == null) |
| throw new NullPointerException(); |
| if (maxBufferCapacity <= 0) |
| throw new IllegalArgumentException("capacity must be positive"); |
| this.executor = executor; |
| this.onNextHandler = handler; |
| this.maxBufferCapacity = roundCapacity(maxBufferCapacity); |
| } |
| |
| /** |
| * Creates a new SubmissionPublisher using the given Executor for |
| * async delivery to subscribers, with the given maximum buffer size |
| * for each subscriber, and no handler for Subscriber exceptions in |
| * method {@link Flow.Subscriber#onNext(Object) onNext}. |
| * |
| * @param executor the executor to use for async delivery, |
| * supporting creation of at least one independent thread |
| * @param maxBufferCapacity the maximum capacity for each |
| * subscriber's buffer (the enforced capacity may be rounded up to |
| * the nearest power of two and/or bounded by the largest value |
| * supported by this implementation; method {@link #getMaxBufferCapacity} |
| * returns the actual value) |
| * @throws NullPointerException if executor is null |
| * @throws IllegalArgumentException if maxBufferCapacity not |
| * positive |
| */ |
| public SubmissionPublisher(Executor executor, int maxBufferCapacity) { |
| this(executor, maxBufferCapacity, null); |
| } |
| |
| /** |
| * Creates a new SubmissionPublisher using the {@link |
| * ForkJoinPool#commonPool()} for async delivery to subscribers |
| * (unless it does not support a parallelism level of at least two, |
| * in which case, a new Thread is created to run each task), with |
| * maximum buffer capacity of {@link Flow#defaultBufferSize}, and no |
| * handler for Subscriber exceptions in method {@link |
| * Flow.Subscriber#onNext(Object) onNext}. |
| */ |
| public SubmissionPublisher() { |
| this(ASYNC_POOL, Flow.defaultBufferSize(), null); |
| } |
| |
| /** |
| * Adds the given Subscriber unless already subscribed. If already |
| * subscribed, the Subscriber's {@link |
| * Flow.Subscriber#onError(Throwable) onError} method is invoked on |
| * the existing subscription with an {@link IllegalStateException}. |
| * Otherwise, upon success, the Subscriber's {@link |
| * Flow.Subscriber#onSubscribe onSubscribe} method is invoked |
| * asynchronously with a new {@link Flow.Subscription}. If {@link |
| * Flow.Subscriber#onSubscribe onSubscribe} throws an exception, the |
| * subscription is cancelled. Otherwise, if this SubmissionPublisher |
| * was closed exceptionally, then the subscriber's {@link |
| * Flow.Subscriber#onError onError} method is invoked with the |
| * corresponding exception, or if closed without exception, the |
| * subscriber's {@link Flow.Subscriber#onComplete() onComplete} |
| * method is invoked. Subscribers may enable receiving items by |
| * invoking the {@link Flow.Subscription#request(long) request} |
| * method of the new Subscription, and may unsubscribe by invoking |
| * its {@link Flow.Subscription#cancel() cancel} method. |
| * |
| * @param subscriber the subscriber |
| * @throws NullPointerException if subscriber is null |
| */ |
| public void subscribe(Flow.Subscriber<? super T> subscriber) { |
| if (subscriber == null) throw new NullPointerException(); |
| BufferedSubscription<T> subscription = |
| new BufferedSubscription<T>(subscriber, executor, |
| onNextHandler, maxBufferCapacity); |
| synchronized (this) { |
| for (BufferedSubscription<T> b = clients, pred = null;;) { |
| if (b == null) { |
| Throwable ex; |
| subscription.onSubscribe(); |
| if ((ex = closedException) != null) |
| subscription.onError(ex); |
| else if (closed) |
| subscription.onComplete(); |
| else if (pred == null) |
| clients = subscription; |
| else |
| pred.next = subscription; |
| break; |
| } |
| BufferedSubscription<T> next = b.next; |
| if (b.isDisabled()) { // remove |
| b.next = null; // detach |
| if (pred == null) |
| clients = next; |
| else |
| pred.next = next; |
| } |
| else if (subscriber.equals(b.subscriber)) { |
| b.onError(new IllegalStateException("Duplicate subscribe")); |
| break; |
| } |
| else |
| pred = b; |
| b = next; |
| } |
| } |
| } |
| |
| /** |
| * Publishes the given item to each current subscriber by |
| * asynchronously invoking its {@link Flow.Subscriber#onNext(Object) |
| * onNext} method, blocking uninterruptibly while resources for any |
| * subscriber are unavailable. This method returns an estimate of |
| * the maximum lag (number of items submitted but not yet consumed) |
| * among all current subscribers. This value is at least one |
| * (accounting for this submitted item) if there are any |
| * subscribers, else zero. |
| * |
| * <p>If the Executor for this publisher throws a |
| * RejectedExecutionException (or any other RuntimeException or |
| * Error) when attempting to asynchronously notify subscribers, |
| * then this exception is rethrown, in which case not all |
| * subscribers will have been issued this item. |
| * |
| * @param item the (non-null) item to publish |
| * @return the estimated maximum lag among subscribers |
| * @throws IllegalStateException if closed |
| * @throws NullPointerException if item is null |
| * @throws RejectedExecutionException if thrown by Executor |
| */ |
| public int submit(T item) { |
| if (item == null) throw new NullPointerException(); |
| int lag = 0; |
| boolean complete; |
| synchronized (this) { |
| complete = closed; |
| BufferedSubscription<T> b = clients; |
| if (!complete) { |
| BufferedSubscription<T> pred = null, r = null, rtail = null; |
| while (b != null) { |
| BufferedSubscription<T> next = b.next; |
| int stat = b.offer(item); |
| if (stat < 0) { // disabled |
| b.next = null; |
| if (pred == null) |
| clients = next; |
| else |
| pred.next = next; |
| } |
| else { |
| if (stat > lag) |
| lag = stat; |
| else if (stat == 0) { // place on retry list |
| b.nextRetry = null; |
| if (rtail == null) |
| r = b; |
| else |
| rtail.nextRetry = b; |
| rtail = b; |
| } |
| pred = b; |
| } |
| b = next; |
| } |
| while (r != null) { |
| BufferedSubscription<T> nextRetry = r.nextRetry; |
| r.nextRetry = null; |
| int stat = r.submit(item); |
| if (stat > lag) |
| lag = stat; |
| else if (stat < 0 && clients == r) |
| clients = r.next; // postpone internal unsubscribes |
| r = nextRetry; |
| } |
| } |
| } |
| if (complete) |
| throw new IllegalStateException("Closed"); |
| else |
| return lag; |
| } |
| |
| /** |
| * Publishes the given item, if possible, to each current subscriber |
| * by asynchronously invoking its {@link |
| * Flow.Subscriber#onNext(Object) onNext} method. The item may be |
| * dropped by one or more subscribers if resource limits are |
| * exceeded, in which case the given handler (if non-null) is |
| * invoked, and if it returns true, retried once. Other calls to |
| * methods in this class by other threads are blocked while the |
| * handler is invoked. Unless recovery is assured, options are |
| * usually limited to logging the error and/or issuing an {@link |
| * Flow.Subscriber#onError(Throwable) onError} signal to the |
| * subscriber. |
| * |
| * <p>This method returns a status indicator: If negative, it |
| * represents the (negative) number of drops (failed attempts to |
| * issue the item to a subscriber). Otherwise it is an estimate of |
| * the maximum lag (number of items submitted but not yet |
| * consumed) among all current subscribers. This value is at least |
| * one (accounting for this submitted item) if there are any |
| * subscribers, else zero. |
| * |
| * <p>If the Executor for this publisher throws a |
| * RejectedExecutionException (or any other RuntimeException or |
| * Error) when attempting to asynchronously notify subscribers, or |
| * the drop handler throws an exception when processing a dropped |
| * item, then this exception is rethrown. |
| * |
| * @param item the (non-null) item to publish |
| * @param onDrop if non-null, the handler invoked upon a drop to a |
| * subscriber, with arguments of the subscriber and item; if it |
| * returns true, an offer is re-attempted (once) |
| * @return if negative, the (negative) number of drops; otherwise |
| * an estimate of maximum lag |
| * @throws IllegalStateException if closed |
| * @throws NullPointerException if item is null |
| * @throws RejectedExecutionException if thrown by Executor |
| */ |
| public int offer(T item, |
| BiPredicate<Flow.Subscriber<? super T>, ? super T> onDrop) { |
| return doOffer(0L, item, onDrop); |
| } |
| |
| /** |
| * Publishes the given item, if possible, to each current subscriber |
| * by asynchronously invoking its {@link |
| * Flow.Subscriber#onNext(Object) onNext} method, blocking while |
| * resources for any subscription are unavailable, up to the |
| * specified timeout or until the caller thread is interrupted, at |
| * which point the given handler (if non-null) is invoked, and if it |
| * returns true, retried once. (The drop handler may distinguish |
| * timeouts from interrupts by checking whether the current thread |
| * is interrupted.) Other calls to methods in this class by other |
| * threads are blocked while the handler is invoked. Unless |
| * recovery is assured, options are usually limited to logging the |
| * error and/or issuing an {@link Flow.Subscriber#onError(Throwable) |
| * onError} signal to the subscriber. |
| * |
| * <p>This method returns a status indicator: If negative, it |
| * represents the (negative) number of drops (failed attempts to |
| * issue the item to a subscriber). Otherwise it is an estimate of |
| * the maximum lag (number of items submitted but not yet |
| * consumed) among all current subscribers. This value is at least |
| * one (accounting for this submitted item) if there are any |
| * subscribers, else zero. |
| * |
| * <p>If the Executor for this publisher throws a |
| * RejectedExecutionException (or any other RuntimeException or |
| * Error) when attempting to asynchronously notify subscribers, or |
| * the drop handler throws an exception when processing a dropped |
| * item, then this exception is rethrown. |
| * |
| * @param item the (non-null) item to publish |
| * @param timeout how long to wait for resources for any subscriber |
| * before giving up, in units of {@code unit} |
| * @param unit a {@code TimeUnit} determining how to interpret the |
| * {@code timeout} parameter |
| * @param onDrop if non-null, the handler invoked upon a drop to a |
| * subscriber, with arguments of the subscriber and item; if it |
| * returns true, an offer is re-attempted (once) |
| * @return if negative, the (negative) number of drops; otherwise |
| * an estimate of maximum lag |
| * @throws IllegalStateException if closed |
| * @throws NullPointerException if item is null |
| * @throws RejectedExecutionException if thrown by Executor |
| */ |
| public int offer(T item, long timeout, TimeUnit unit, |
| BiPredicate<Flow.Subscriber<? super T>, ? super T> onDrop) { |
| return doOffer(unit.toNanos(timeout), item, onDrop); |
| } |
| |
| /** Common implementation for both forms of offer */ |
| final int doOffer(long nanos, T item, |
| BiPredicate<Flow.Subscriber<? super T>, ? super T> onDrop) { |
| if (item == null) throw new NullPointerException(); |
| int lag = 0, drops = 0; |
| boolean complete; |
| synchronized (this) { |
| complete = closed; |
| BufferedSubscription<T> b = clients; |
| if (!complete) { |
| BufferedSubscription<T> pred = null, r = null, rtail = null; |
| while (b != null) { |
| BufferedSubscription<T> next = b.next; |
| int stat = b.offer(item); |
| if (stat < 0) { |
| b.next = null; |
| if (pred == null) |
| clients = next; |
| else |
| pred.next = next; |
| } |
| else { |
| if (stat > lag) |
| lag = stat; |
| else if (stat == 0) { |
| b.nextRetry = null; |
| if (rtail == null) |
| r = b; |
| else |
| rtail.nextRetry = b; |
| rtail = b; |
| } |
| else if (stat > lag) |
| lag = stat; |
| pred = b; |
| } |
| b = next; |
| } |
| while (r != null) { |
| BufferedSubscription<T> nextRetry = r.nextRetry; |
| r.nextRetry = null; |
| int stat = (nanos > 0L) |
| ? r.timedOffer(item, nanos) |
| : r.offer(item); |
| if (stat == 0 && onDrop != null && |
| onDrop.test(r.subscriber, item)) |
| stat = r.offer(item); |
| if (stat == 0) |
| ++drops; |
| else if (stat > lag) |
| lag = stat; |
| else if (stat < 0 && clients == r) |
| clients = r.next; |
| r = nextRetry; |
| } |
| } |
| } |
| if (complete) |
| throw new IllegalStateException("Closed"); |
| else |
| return (drops > 0) ? -drops : lag; |
| } |
| |
| /** |
| * Unless already closed, issues {@link |
| * Flow.Subscriber#onComplete() onComplete} signals to current |
| * subscribers, and disallows subsequent attempts to publish. |
| * Upon return, this method does <em>NOT</em> guarantee that all |
| * subscribers have yet completed. |
| */ |
| public void close() { |
| if (!closed) { |
| BufferedSubscription<T> b; |
| synchronized (this) { |
| b = clients; |
| clients = null; |
| closed = true; |
| } |
| while (b != null) { |
| BufferedSubscription<T> next = b.next; |
| b.next = null; |
| b.onComplete(); |
| b = next; |
| } |
| } |
| } |
| |
| /** |
| * Unless already closed, issues {@link |
| * Flow.Subscriber#onError(Throwable) onError} signals to current |
| * subscribers with the given error, and disallows subsequent |
| * attempts to publish. Future subscribers also receive the given |
| * error. Upon return, this method does <em>NOT</em> guarantee |
| * that all subscribers have yet completed. |
| * |
| * @param error the {@code onError} argument sent to subscribers |
| * @throws NullPointerException if error is null |
| */ |
| public void closeExceptionally(Throwable error) { |
| if (error == null) |
| throw new NullPointerException(); |
| if (!closed) { |
| BufferedSubscription<T> b; |
| synchronized (this) { |
| b = clients; |
| clients = null; |
| closed = true; |
| closedException = error; |
| } |
| while (b != null) { |
| BufferedSubscription<T> next = b.next; |
| b.next = null; |
| b.onError(error); |
| b = next; |
| } |
| } |
| } |
| |
| /** |
| * Returns true if this publisher is not accepting submissions. |
| * |
| * @return true if closed |
| */ |
| public boolean isClosed() { |
| return closed; |
| } |
| |
| /** |
| * Returns the exception associated with {@link |
| * #closeExceptionally(Throwable) closeExceptionally}, or null if |
| * not closed or if closed normally. |
| * |
| * @return the exception, or null if none |
| */ |
| public Throwable getClosedException() { |
| return closedException; |
| } |
| |
| /** |
| * Returns true if this publisher has any subscribers. |
| * |
| * @return true if this publisher has any subscribers |
| */ |
| public boolean hasSubscribers() { |
| boolean nonEmpty = false; |
| if (!closed) { |
| synchronized (this) { |
| for (BufferedSubscription<T> b = clients; b != null;) { |
| BufferedSubscription<T> next = b.next; |
| if (b.isDisabled()) { |
| b.next = null; |
| b = clients = next; |
| } |
| else { |
| nonEmpty = true; |
| break; |
| } |
| } |
| } |
| } |
| return nonEmpty; |
| } |
| |
| /** |
| * Returns the number of current subscribers. |
| * |
| * @return the number of current subscribers |
| */ |
| public int getNumberOfSubscribers() { |
| int count = 0; |
| if (!closed) { |
| synchronized (this) { |
| BufferedSubscription<T> pred = null, next; |
| for (BufferedSubscription<T> b = clients; b != null; b = next) { |
| next = b.next; |
| if (b.isDisabled()) { |
| b.next = null; |
| if (pred == null) |
| clients = next; |
| else |
| pred.next = next; |
| } |
| else { |
| pred = b; |
| ++count; |
| } |
| } |
| } |
| } |
| return count; |
| } |
| |
| /** |
| * Returns the Executor used for asynchronous delivery. |
| * |
| * @return the Executor used for asynchronous delivery |
| */ |
| public Executor getExecutor() { |
| return executor; |
| } |
| |
| /** |
| * Returns the maximum per-subscriber buffer capacity. |
| * |
| * @return the maximum per-subscriber buffer capacity |
| */ |
| public int getMaxBufferCapacity() { |
| return maxBufferCapacity; |
| } |
| |
| /** |
| * Returns a list of current subscribers for monitoring and |
| * tracking purposes, not for invoking {@link Flow.Subscriber} |
| * methods on the subscribers. |
| * |
| * @return list of current subscribers |
| */ |
| public List<Flow.Subscriber<? super T>> getSubscribers() { |
| ArrayList<Flow.Subscriber<? super T>> subs = new ArrayList<>(); |
| synchronized (this) { |
| BufferedSubscription<T> pred = null, next; |
| for (BufferedSubscription<T> b = clients; b != null; b = next) { |
| next = b.next; |
| if (b.isDisabled()) { |
| b.next = null; |
| if (pred == null) |
| clients = next; |
| else |
| pred.next = next; |
| } |
| else |
| subs.add(b.subscriber); |
| } |
| } |
| return subs; |
| } |
| |
| /** |
| * Returns true if the given Subscriber is currently subscribed. |
| * |
| * @param subscriber the subscriber |
| * @return true if currently subscribed |
| * @throws NullPointerException if subscriber is null |
| */ |
| public boolean isSubscribed(Flow.Subscriber<? super T> subscriber) { |
| if (subscriber == null) throw new NullPointerException(); |
| if (!closed) { |
| synchronized (this) { |
| BufferedSubscription<T> pred = null, next; |
| for (BufferedSubscription<T> b = clients; b != null; b = next) { |
| next = b.next; |
| if (b.isDisabled()) { |
| b.next = null; |
| if (pred == null) |
| clients = next; |
| else |
| pred.next = next; |
| } |
| else if (subscriber.equals(b.subscriber)) |
| return true; |
| else |
| pred = b; |
| } |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Returns an estimate of the minimum number of items requested |
| * (via {@link Flow.Subscription#request(long) request}) but not |
| * yet produced, among all current subscribers. |
| * |
| * @return the estimate, or zero if no subscribers |
| */ |
| public long estimateMinimumDemand() { |
| long min = Long.MAX_VALUE; |
| boolean nonEmpty = false; |
| synchronized (this) { |
| BufferedSubscription<T> pred = null, next; |
| for (BufferedSubscription<T> b = clients; b != null; b = next) { |
| int n; long d; |
| next = b.next; |
| if ((n = b.estimateLag()) < 0) { |
| b.next = null; |
| if (pred == null) |
| clients = next; |
| else |
| pred.next = next; |
| } |
| else { |
| if ((d = b.demand - n) < min) |
| min = d; |
| nonEmpty = true; |
| pred = b; |
| } |
| } |
| } |
| return nonEmpty ? min : 0; |
| } |
| |
| /** |
| * Returns an estimate of the maximum number of items produced but |
| * not yet consumed among all current subscribers. |
| * |
| * @return the estimate |
| */ |
| public int estimateMaximumLag() { |
| int max = 0; |
| synchronized (this) { |
| BufferedSubscription<T> pred = null, next; |
| for (BufferedSubscription<T> b = clients; b != null; b = next) { |
| int n; |
| next = b.next; |
| if ((n = b.estimateLag()) < 0) { |
| b.next = null; |
| if (pred == null) |
| clients = next; |
| else |
| pred.next = next; |
| } |
| else { |
| if (n > max) |
| max = n; |
| pred = b; |
| } |
| } |
| } |
| return max; |
| } |
| |
| /** |
| * Processes all published items using the given Consumer function. |
| * Returns a CompletableFuture that is completed normally when this |
| * publisher signals {@link Flow.Subscriber#onComplete() |
| * onComplete}, or completed exceptionally upon any error, or an |
| * exception is thrown by the Consumer, or the returned |
| * CompletableFuture is cancelled, in which case no further items |
| * are processed. |
| * |
| * @param consumer the function applied to each onNext item |
| * @return a CompletableFuture that is completed normally |
| * when the publisher signals onComplete, and exceptionally |
| * upon any error or cancellation |
| * @throws NullPointerException if consumer is null |
| */ |
| public CompletableFuture<Void> consume(Consumer<? super T> consumer) { |
| if (consumer == null) |
| throw new NullPointerException(); |
| CompletableFuture<Void> status = new CompletableFuture<>(); |
| subscribe(new ConsumerSubscriber<T>(status, consumer)); |
| return status; |
| } |
| |
| /** Subscriber for method consume */ |
| private static final class ConsumerSubscriber<T> |
| implements Flow.Subscriber<T> { |
| final CompletableFuture<Void> status; |
| final Consumer<? super T> consumer; |
| Flow.Subscription subscription; |
| ConsumerSubscriber(CompletableFuture<Void> status, |
| Consumer<? super T> consumer) { |
| this.status = status; this.consumer = consumer; |
| } |
| public final void onSubscribe(Flow.Subscription subscription) { |
| this.subscription = subscription; |
| status.whenComplete((v, e) -> subscription.cancel()); |
| if (!status.isDone()) |
| subscription.request(Long.MAX_VALUE); |
| } |
| public final void onError(Throwable ex) { |
| status.completeExceptionally(ex); |
| } |
| public final void onComplete() { |
| status.complete(null); |
| } |
| public final void onNext(T item) { |
| try { |
| consumer.accept(item); |
| } catch (Throwable ex) { |
| subscription.cancel(); |
| status.completeExceptionally(ex); |
| } |
| } |
| } |
| |
| /** |
| * A task for consuming buffer items and signals, created and |
| * executed whenever they become available. A task consumes as |
| * many items/signals as possible before terminating, at which |
| * point another task is created when needed. The dual Runnable |
| * and ForkJoinTask declaration saves overhead when executed by |
| * ForkJoinPools, without impacting other kinds of Executors. |
| */ |
| @SuppressWarnings("serial") |
| static final class ConsumerTask<T> extends ForkJoinTask<Void> |
| implements Runnable, CompletableFuture.AsynchronousCompletionTask { |
| final BufferedSubscription<T> consumer; |
| ConsumerTask(BufferedSubscription<T> consumer) { |
| this.consumer = consumer; |
| } |
| public final Void getRawResult() { return null; } |
| public final void setRawResult(Void v) {} |
| public final boolean exec() { consumer.consume(); return false; } |
| public final void run() { consumer.consume(); } |
| } |
| |
| /** |
| * A bounded (ring) buffer with integrated control to start a |
| * consumer task whenever items are available. The buffer |
| * algorithm is similar to one used inside ForkJoinPool (see its |
| * internal documentation for details) specialized for the case of |
| * at most one concurrent producer and consumer, and power of two |
| * buffer sizes. This allows methods to operate without locks even |
| * while supporting resizing, blocking, task-triggering, and |
| * garbage-free buffers (nulling out elements when consumed), |
| * although supporting these does impose a bit of overhead |
| * compared to plain fixed-size ring buffers. |
| * |
| * The publisher guarantees a single producer via its lock. We |
| * ensure in this class that there is at most one consumer. The |
| * request and cancel methods must be fully thread-safe but are |
| * coded to exploit the most common case in which they are only |
| * called by consumers (usually within onNext). |
| * |
| * Execution control is managed using the ACTIVE ctl bit. We |
| * ensure that a task is active when consumable items (and |
| * usually, SUBSCRIBE, ERROR or COMPLETE signals) are present and |
| * there is demand (unfilled requests). This is complicated on |
| * the creation side by the possibility of exceptions when trying |
| * to execute tasks. These eventually force DISABLED state, but |
| * sometimes not directly. On the task side, termination (clearing |
| * ACTIVE) that would otherwise race with producers or request() |
| * calls uses the CONSUME keep-alive bit to force a recheck. |
| * |
| * The ctl field also manages run state. When DISABLED, no further |
| * updates are possible. Disabling may be preceded by setting |
| * ERROR or COMPLETE (or both -- ERROR has precedence), in which |
| * case the associated Subscriber methods are invoked, possibly |
| * synchronously if there is no active consumer task (including |
| * cases where execute() failed). The cancel() method is supported |
| * by treating as ERROR but suppressing onError signal. |
| * |
| * Support for blocking also exploits the fact that there is only |
| * one possible waiter. ManagedBlocker-compatible control fields |
| * are placed in this class itself rather than in wait-nodes. |
| * Blocking control relies on the "waiter" field. Producers set |
| * the field before trying to block, but must then recheck (via |
| * offer) before parking. Signalling then just unparks and clears |
| * waiter field. If the producer and/or consumer are using a |
| * ForkJoinPool, the producer attempts to help run consumer tasks |
| * via ForkJoinPool.helpAsyncBlocker before blocking. |
| * |
| * This class uses @Contended and heuristic field declaration |
| * ordering to reduce false-sharing-based memory contention among |
| * instances of BufferedSubscription, but it does not currently |
| * attempt to avoid memory contention among buffers. This field |
| * and element packing can hurt performance especially when each |
| * publisher has only one client operating at a high rate. |
| * Addressing this may require allocating substantially more space |
| * than users expect. |
| */ |
| @SuppressWarnings("serial") |
| @jdk.internal.vm.annotation.Contended |
| private static final class BufferedSubscription<T> |
| implements Flow.Subscription, ForkJoinPool.ManagedBlocker { |
| // Order-sensitive field declarations |
| long timeout; // > 0 if timed wait |
| volatile long demand; // # unfilled requests |
| int maxCapacity; // reduced on OOME |
| int putStat; // offer result for ManagedBlocker |
| volatile int ctl; // atomic run state flags |
| volatile int head; // next position to take |
| int tail; // next position to put |
| Object[] array; // buffer: null if disabled |
| Flow.Subscriber<? super T> subscriber; // null if disabled |
| Executor executor; // null if disabled |
| BiConsumer<? super Flow.Subscriber<? super T>, ? super Throwable> onNextHandler; |
| volatile Throwable pendingError; // holds until onError issued |
| volatile Thread waiter; // blocked producer thread |
| T putItem; // for offer within ManagedBlocker |
| BufferedSubscription<T> next; // used only by publisher |
| BufferedSubscription<T> nextRetry; // used only by publisher |
| |
| // ctl values |
| static final int ACTIVE = 0x01; // consumer task active |
| static final int CONSUME = 0x02; // keep-alive for consumer task |
| static final int DISABLED = 0x04; // final state |
| static final int ERROR = 0x08; // signal onError then disable |
| static final int SUBSCRIBE = 0x10; // signal onSubscribe |
| static final int COMPLETE = 0x20; // signal onComplete when done |
| |
| static final long INTERRUPTED = -1L; // timeout vs interrupt sentinel |
| |
| /** |
| * Initial buffer capacity used when maxBufferCapacity is |
| * greater. Must be a power of two. |
| */ |
| static final int DEFAULT_INITIAL_CAP = 32; |
| |
| BufferedSubscription(Flow.Subscriber<? super T> subscriber, |
| Executor executor, |
| BiConsumer<? super Flow.Subscriber<? super T>, |
| ? super Throwable> onNextHandler, |
| int maxBufferCapacity) { |
| this.subscriber = subscriber; |
| this.executor = executor; |
| this.onNextHandler = onNextHandler; |
| this.maxCapacity = maxBufferCapacity; |
| this.array = new Object[maxBufferCapacity < DEFAULT_INITIAL_CAP ? |
| (maxBufferCapacity < 2 ? // at least 2 slots |
| 2 : maxBufferCapacity) : |
| DEFAULT_INITIAL_CAP]; |
| } |
| |
| final boolean isDisabled() { |
| return ctl == DISABLED; |
| } |
| |
| /** |
| * Returns estimated number of buffered items, or -1 if |
| * disabled. |
| */ |
| final int estimateLag() { |
| int n; |
| return (ctl == DISABLED) ? -1 : ((n = tail - head) > 0) ? n : 0; |
| } |
| |
| /** |
| * Tries to add item and start consumer task if necessary. |
| * @return -1 if disabled, 0 if dropped, else estimated lag |
| */ |
| final int offer(T item) { |
| int h = head, t = tail, cap, size, stat; |
| Object[] a = array; |
| if (a != null && (cap = a.length) > 0 && cap >= (size = t + 1 - h)) { |
| a[(cap - 1) & t] = item; // relaxed writes OK |
| tail = t + 1; |
| stat = size; |
| } |
| else |
| stat = growAndAdd(a, item); |
| return (stat > 0 && |
| (ctl & (ACTIVE | CONSUME)) != (ACTIVE | CONSUME)) ? |
| startOnOffer(stat) : stat; |
| } |
| |
| /** |
| * Tries to create or expand buffer, then adds item if possible. |
| */ |
| private int growAndAdd(Object[] a, T item) { |
| boolean alloc; |
| int cap, stat; |
| if ((ctl & (ERROR | DISABLED)) != 0) { |
| cap = 0; |
| stat = -1; |
| alloc = false; |
| } |
| else if (a == null || (cap = a.length) <= 0) { |
| cap = 0; |
| stat = 1; |
| alloc = true; |
| } |
| else { |
| VarHandle.fullFence(); // recheck |
| int h = head, t = tail, size = t + 1 - h; |
| if (cap >= size) { |
| a[(cap - 1) & t] = item; |
| tail = t + 1; |
| stat = size; |
| alloc = false; |
| } |
| else if (cap >= maxCapacity) { |
| stat = 0; // cannot grow |
| alloc = false; |
| } |
| else { |
| stat = cap + 1; |
| alloc = true; |
| } |
| } |
| if (alloc) { |
| int newCap = (cap > 0) ? cap << 1 : 1; |
| if (newCap <= cap) |
| stat = 0; |
| else { |
| Object[] newArray = null; |
| try { |
| newArray = new Object[newCap]; |
| } catch (Throwable ex) { // try to cope with OOME |
| } |
| if (newArray == null) { |
| if (cap > 0) |
| maxCapacity = cap; // avoid continuous failure |
| stat = 0; |
| } |
| else { |
| array = newArray; |
| int t = tail; |
| int newMask = newCap - 1; |
| if (a != null && cap > 0) { |
| int mask = cap - 1; |
| for (int j = head; j != t; ++j) { |
| int k = j & mask; |
| Object x = QA.getAcquire(a, k); |
| if (x != null && // races with consumer |
| QA.compareAndSet(a, k, x, null)) |
| newArray[j & newMask] = x; |
| } |
| } |
| newArray[t & newMask] = item; |
| tail = t + 1; |
| } |
| } |
| } |
| return stat; |
| } |
| |
| /** |
| * Spins/helps/blocks while offer returns 0. Called only if |
| * initial offer return 0. |
| */ |
| final int submit(T item) { |
| int stat; |
| if ((stat = offer(item)) == 0) { |
| putItem = item; |
| timeout = 0L; |
| putStat = 0; |
| ForkJoinPool.helpAsyncBlocker(executor, this); |
| if ((stat = putStat) == 0) { |
| try { |
| ForkJoinPool.managedBlock(this); |
| } catch (InterruptedException ie) { |
| timeout = INTERRUPTED; |
| } |
| stat = putStat; |
| } |
| if (timeout < 0L) |
| Thread.currentThread().interrupt(); |
| } |
| return stat; |
| } |
| |
| /** |
| * Timeout version; similar to submit. |
| */ |
| final int timedOffer(T item, long nanos) { |
| int stat; |
| if ((stat = offer(item)) == 0 && (timeout = nanos) > 0L) { |
| putItem = item; |
| putStat = 0; |
| ForkJoinPool.helpAsyncBlocker(executor, this); |
| if ((stat = putStat) == 0) { |
| try { |
| ForkJoinPool.managedBlock(this); |
| } catch (InterruptedException ie) { |
| timeout = INTERRUPTED; |
| } |
| stat = putStat; |
| } |
| if (timeout < 0L) |
| Thread.currentThread().interrupt(); |
| } |
| return stat; |
| } |
| |
| /** |
| * Tries to start consumer task after offer. |
| * @return -1 if now disabled, else argument |
| */ |
| private int startOnOffer(int stat) { |
| for (;;) { |
| Executor e; int c; |
| if ((c = ctl) == DISABLED || (e = executor) == null) { |
| stat = -1; |
| break; |
| } |
| else if ((c & ACTIVE) != 0) { // ensure keep-alive |
| if ((c & CONSUME) != 0 || |
| CTL.compareAndSet(this, c, c | CONSUME)) |
| break; |
| } |
| else if (demand == 0L || tail == head) |
| break; |
| else if (CTL.compareAndSet(this, c, c | (ACTIVE | CONSUME))) { |
| try { |
| e.execute(new ConsumerTask<T>(this)); |
| break; |
| } catch (RuntimeException | Error ex) { // back out |
| do {} while (((c = ctl) & DISABLED) == 0 && |
| (c & ACTIVE) != 0 && |
| !CTL.weakCompareAndSet |
| (this, c, c & ~ACTIVE)); |
| throw ex; |
| } |
| } |
| } |
| return stat; |
| } |
| |
| private void signalWaiter(Thread w) { |
| waiter = null; |
| LockSupport.unpark(w); // release producer |
| } |
| |
| /** |
| * Nulls out most fields, mainly to avoid garbage retention |
| * until publisher unsubscribes, but also to help cleanly stop |
| * upon error by nulling required components. |
| */ |
| private void detach() { |
| Thread w = waiter; |
| executor = null; |
| subscriber = null; |
| pendingError = null; |
| signalWaiter(w); |
| } |
| |
| /** |
| * Issues error signal, asynchronously if a task is running, |
| * else synchronously. |
| */ |
| final void onError(Throwable ex) { |
| for (int c;;) { |
| if (((c = ctl) & (ERROR | DISABLED)) != 0) |
| break; |
| else if ((c & ACTIVE) != 0) { |
| pendingError = ex; |
| if (CTL.compareAndSet(this, c, c | ERROR)) |
| break; // cause consumer task to exit |
| } |
| else if (CTL.compareAndSet(this, c, DISABLED)) { |
| Flow.Subscriber<? super T> s = subscriber; |
| if (s != null && ex != null) { |
| try { |
| s.onError(ex); |
| } catch (Throwable ignore) { |
| } |
| } |
| detach(); |
| break; |
| } |
| } |
| } |
| |
| /** |
| * Tries to start consumer task upon a signal or request; |
| * disables on failure. |
| */ |
| private void startOrDisable() { |
| Executor e; |
| if ((e = executor) != null) { // skip if already disabled |
| try { |
| e.execute(new ConsumerTask<T>(this)); |
| } catch (Throwable ex) { // back out and force signal |
| for (int c;;) { |
| if ((c = ctl) == DISABLED || (c & ACTIVE) == 0) |
| break; |
| if (CTL.compareAndSet(this, c, c & ~ACTIVE)) { |
| onError(ex); |
| break; |
| } |
| } |
| } |
| } |
| } |
| |
| final void onComplete() { |
| for (int c;;) { |
| if ((c = ctl) == DISABLED) |
| break; |
| if (CTL.compareAndSet(this, c, |
| c | (ACTIVE | CONSUME | COMPLETE))) { |
| if ((c & ACTIVE) == 0) |
| startOrDisable(); |
| break; |
| } |
| } |
| } |
| |
| final void onSubscribe() { |
| for (int c;;) { |
| if ((c = ctl) == DISABLED) |
| break; |
| if (CTL.compareAndSet(this, c, |
| c | (ACTIVE | CONSUME | SUBSCRIBE))) { |
| if ((c & ACTIVE) == 0) |
| startOrDisable(); |
| break; |
| } |
| } |
| } |
| |
| /** |
| * Causes consumer task to exit if active (without reporting |
| * onError unless there is already a pending error), and |
| * disables. |
| */ |
| public void cancel() { |
| for (int c;;) { |
| if ((c = ctl) == DISABLED) |
| break; |
| else if ((c & ACTIVE) != 0) { |
| if (CTL.compareAndSet(this, c, |
| c | (CONSUME | ERROR))) |
| break; |
| } |
| else if (CTL.compareAndSet(this, c, DISABLED)) { |
| detach(); |
| break; |
| } |
| } |
| } |
| |
| /** |
| * Adds to demand and possibly starts task. |
| */ |
| public void request(long n) { |
| if (n > 0L) { |
| for (;;) { |
| long prev = demand, d; |
| if ((d = prev + n) < prev) // saturate |
| d = Long.MAX_VALUE; |
| if (DEMAND.compareAndSet(this, prev, d)) { |
| for (int c, h;;) { |
| if ((c = ctl) == DISABLED) |
| break; |
| else if ((c & ACTIVE) != 0) { |
| if ((c & CONSUME) != 0 || |
| CTL.compareAndSet(this, c, c | CONSUME)) |
| break; |
| } |
| else if ((h = head) != tail) { |
| if (CTL.compareAndSet(this, c, |
| c | (ACTIVE|CONSUME))) { |
| startOrDisable(); |
| break; |
| } |
| } |
| else if (head == h && tail == h) |
| break; // else stale |
| if (demand == 0L) |
| break; |
| } |
| break; |
| } |
| } |
| } |
| else if (n < 0L) |
| onError(new IllegalArgumentException( |
| "negative subscription request")); |
| } |
| |
| public final boolean isReleasable() { // for ManagedBlocker |
| T item = putItem; |
| if (item != null) { |
| if ((putStat = offer(item)) == 0) |
| return false; |
| putItem = null; |
| } |
| return true; |
| } |
| |
| public final boolean block() { // for ManagedBlocker |
| T item = putItem; |
| if (item != null) { |
| putItem = null; |
| long nanos = timeout; |
| long deadline = (nanos > 0L) ? System.nanoTime() + nanos : 0L; |
| while ((putStat = offer(item)) == 0) { |
| if (Thread.interrupted()) { |
| timeout = INTERRUPTED; |
| if (nanos > 0L) |
| break; |
| } |
| else if (nanos > 0L && |
| (nanos = deadline - System.nanoTime()) <= 0L) |
| break; |
| else if (waiter == null) |
| waiter = Thread.currentThread(); |
| else { |
| if (nanos > 0L) |
| LockSupport.parkNanos(this, nanos); |
| else |
| LockSupport.park(this); |
| waiter = null; |
| } |
| } |
| } |
| waiter = null; |
| return true; |
| } |
| |
| /** |
| * Consumer loop, called from ConsumerTask, or indirectly |
| * when helping during submit. |
| */ |
| final void consume() { |
| Flow.Subscriber<? super T> s; |
| int h = head; |
| if ((s = subscriber) != null) { // else disabled |
| for (;;) { |
| long d = demand; |
| int c; Object[] a; int n, i; Object x; Thread w; |
| if (((c = ctl) & (ERROR | SUBSCRIBE | DISABLED)) != 0) { |
| if (!checkControl(s, c)) |
| break; |
| } |
| else if ((a = array) == null || h == tail || |
| (n = a.length) == 0 || |
| (x = QA.getAcquire(a, i = (n - 1) & h)) == null) { |
| if (!checkEmpty(s, c)) |
| break; |
| } |
| else if (d == 0L) { |
| if (!checkDemand(c)) |
| break; |
| } |
| else if (((c & CONSUME) != 0 || |
| CTL.compareAndSet(this, c, c | CONSUME)) && |
| QA.compareAndSet(a, i, x, null)) { |
| HEAD.setRelease(this, ++h); |
| DEMAND.getAndAdd(this, -1L); |
| if ((w = waiter) != null) |
| signalWaiter(w); |
| try { |
| @SuppressWarnings("unchecked") T y = (T) x; |
| s.onNext(y); |
| } catch (Throwable ex) { |
| handleOnNext(s, ex); |
| } |
| } |
| } |
| } |
| } |
| |
| /** |
| * Responds to control events in consume(). |
| */ |
| private boolean checkControl(Flow.Subscriber<? super T> s, int c) { |
| boolean stat = true; |
| if ((c & SUBSCRIBE) != 0) { |
| if (CTL.compareAndSet(this, c, c & ~SUBSCRIBE)) { |
| try { |
| if (s != null) |
| s.onSubscribe(this); |
| } catch (Throwable ex) { |
| onError(ex); |
| } |
| } |
| } |
| else if ((c & ERROR) != 0) { |
| Throwable ex = pendingError; |
| ctl = DISABLED; // no need for CAS |
| if (ex != null) { // null if errorless cancel |
| try { |
| if (s != null) |
| s.onError(ex); |
| } catch (Throwable ignore) { |
| } |
| } |
| } |
| else { |
| detach(); |
| stat = false; |
| } |
| return stat; |
| } |
| |
| /** |
| * Responds to apparent emptiness in consume(). |
| */ |
| private boolean checkEmpty(Flow.Subscriber<? super T> s, int c) { |
| boolean stat = true; |
| if (head == tail) { |
| if ((c & CONSUME) != 0) |
| CTL.compareAndSet(this, c, c & ~CONSUME); |
| else if ((c & COMPLETE) != 0) { |
| if (CTL.compareAndSet(this, c, DISABLED)) { |
| try { |
| if (s != null) |
| s.onComplete(); |
| } catch (Throwable ignore) { |
| } |
| } |
| } |
| else if (CTL.compareAndSet(this, c, c & ~ACTIVE)) |
| stat = false; |
| } |
| return stat; |
| } |
| |
| /** |
| * Responds to apparent zero demand in consume(). |
| */ |
| private boolean checkDemand(int c) { |
| boolean stat = true; |
| if (demand == 0L) { |
| if ((c & CONSUME) != 0) |
| CTL.compareAndSet(this, c, c & ~CONSUME); |
| else if (CTL.compareAndSet(this, c, c & ~ACTIVE)) |
| stat = false; |
| } |
| return stat; |
| } |
| |
| /** |
| * Processes exception in Subscriber.onNext. |
| */ |
| private void handleOnNext(Flow.Subscriber<? super T> s, Throwable ex) { |
| BiConsumer<? super Flow.Subscriber<? super T>, ? super Throwable> h; |
| if ((h = onNextHandler) != null) { |
| try { |
| h.accept(s, ex); |
| } catch (Throwable ignore) { |
| } |
| } |
| onError(ex); |
| } |
| |
| // VarHandle mechanics |
| private static final VarHandle CTL; |
| private static final VarHandle TAIL; |
| private static final VarHandle HEAD; |
| private static final VarHandle DEMAND; |
| private static final VarHandle QA; |
| |
| static { |
| try { |
| MethodHandles.Lookup l = MethodHandles.lookup(); |
| CTL = l.findVarHandle(BufferedSubscription.class, "ctl", |
| int.class); |
| TAIL = l.findVarHandle(BufferedSubscription.class, "tail", |
| int.class); |
| HEAD = l.findVarHandle(BufferedSubscription.class, "head", |
| int.class); |
| DEMAND = l.findVarHandle(BufferedSubscription.class, "demand", |
| long.class); |
| QA = MethodHandles.arrayElementVarHandle(Object[].class); |
| } catch (ReflectiveOperationException e) { |
| throw new Error(e); |
| } |
| |
| // Reduce the risk of rare disastrous classloading in first call to |
| // LockSupport.park: https://bugs.openjdk.java.net/browse/JDK-8074773 |
| Class<?> ensureLoaded = LockSupport.class; |
| } |
| } |
| } |
