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/*
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
 * the License for the specific language governing permissions and limitations under the License.
 */

package io.reactivex.rxjava3.processors;

import java.util.concurrent.atomic.*;

import org.reactivestreams.*;

import io.reactivex.rxjava3.annotations.*;
import io.reactivex.rxjava3.exceptions.*;
import io.reactivex.rxjava3.internal.functions.ObjectHelper;
import io.reactivex.rxjava3.internal.subscriptions.*;
import io.reactivex.rxjava3.internal.util.*;
import io.reactivex.rxjava3.operators.*;
import io.reactivex.rxjava3.plugins.RxJavaPlugins;

/**
 * A {@link FlowableProcessor} implementation that coordinates downstream requests through
 * a front-buffer and stable-prefetching, optionally canceling the upstream if all
 * subscribers have cancelled.
 * 

* *

* This processor does not have a public constructor by design; a new empty instance of this * {@code MulticastProcessor} can be created via the following {@code create} methods that * allow configuring it: *

    *
  • {@link #create()}: create an empty {@code MulticastProcessor} with * {@link io.reactivex.rxjava3.core.Flowable#bufferSize() Flowable.bufferSize()} prefetch amount * and no reference counting behavior.
  • *
  • {@link #create(int)}: create an empty {@code MulticastProcessor} with * the given prefetch amount and no reference counting behavior.
  • *
  • {@link #create(boolean)}: create an empty {@code MulticastProcessor} with * {@link io.reactivex.rxjava3.core.Flowable#bufferSize() Flowable.bufferSize()} prefetch amount * and an optional reference counting behavior.
  • *
  • {@link #create(int, boolean)}: create an empty {@code MulticastProcessor} with * the given prefetch amount and an optional reference counting behavior.
  • *
*

* When the reference counting behavior is enabled, the {@code MulticastProcessor} cancels its * upstream when all {@link Subscriber}s have cancelled. Late {@code Subscriber}s will then be * immediately completed. *

* Because {@code MulticastProcessor} implements the {@link Subscriber} interface, calling * {@code onSubscribe} is mandatory (Rule 2.12). * If {@code MulticastProcessor} should run standalone, i.e., without subscribing the {@code MulticastProcessor} to another {@link Publisher}, * use {@link #start()} or {@link #startUnbounded()} methods to initialize the internal buffer. * Failing to do so will lead to a {@link NullPointerException} at runtime. *

* Use {@link #offer(Object)} to try and offer/emit items but don't fail if the * internal buffer is full. *

* A {@code MulticastProcessor} is a {@link Processor} type in the Reactive Streams specification, * {@code null}s are not allowed (Rule 2.13) as * parameters to {@link #onSubscribe(Subscription)}, {@link #offer(Object)}, {@link #onNext(Object)} and {@link #onError(Throwable)}. * Such calls will result in a {@link NullPointerException} being thrown and the processor's state is not changed. *

* Since a {@code MulticastProcessor} is a {@link io.reactivex.rxjava3.core.Flowable}, it supports backpressure. * The backpressure from the currently subscribed {@link Subscriber}s are coordinated by emitting upstream * items only if all of those {@code Subscriber}s have requested at least one item. This behavior * is also called lockstep-mode because even if some {@code Subscriber}s can take any number * of items, other {@code Subscriber}s requesting less or infrequently will slow down the overall * throughput of the flow. *

* Calling {@link #onNext(Object)}, {@link #offer(Object)}, {@link #onError(Throwable)} and {@link #onComplete()} * is required to be serialized (called from the same thread or called non-overlappingly from different threads * through external means of serialization). The {@link #toSerialized()} method available to all {@link FlowableProcessor}s * provides such serialization and also protects against reentrance (i.e., when a downstream {@code Subscriber} * consuming this processor also wants to call {@link #onNext(Object)} on this processor recursively). *

* This {@code MulticastProcessor} supports the standard state-peeking methods {@link #hasComplete()}, {@link #hasThrowable()}, * {@link #getThrowable()} and {@link #hasSubscribers()}. This processor doesn't allow peeking into its buffer. *

* When this {@code MulticastProcessor} is terminated via {@link #onError(Throwable)} or {@link #onComplete()}, * all previously signaled but not yet consumed items will be still available to {@code Subscriber}s and the respective * terminal even is only emitted when all previous items have been successfully delivered to {@code Subscriber}s. * If there are no {@code Subscriber}s, the remaining items will be buffered indefinitely. *

* The {@code MulticastProcessor} does not support clearing its cached events (to appear empty again). *

*
Backpressure:
*
The backpressure from the currently subscribed {@code Subscriber}s are coordinated by emitting upstream * items only if all of those {@code Subscriber}s have requested at least one item. This behavior * is also called lockstep-mode because even if some {@code Subscriber}s can take any number * of items, other {@code Subscriber}s requesting less or infrequently will slow down the overall * throughput of the flow.
*
Scheduler:
*
{@code MulticastProcessor} does not operate by default on a particular {@link io.reactivex.rxjava3.core.Scheduler} and * the {@code Subscriber}s get notified on an arbitrary thread in a serialized fashion.
*
*

* Example: *


    MulticastProcessor<Integer> mp = Flowable.range(1, 10)
    .subscribeWith(MulticastProcessor.create());

    mp.test().assertResult(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

    // --------------------

    MulticastProcessor<Integer> mp2 = MulticastProcessor.create(4);
    mp2.start();

    assertTrue(mp2.offer(1));
    assertTrue(mp2.offer(2));
    assertTrue(mp2.offer(3));
    assertTrue(mp2.offer(4));

    assertFalse(mp2.offer(5));

    mp2.onComplete();

    mp2.test().assertResult(1, 2, 3, 4);
 * 
*

History: 2.1.14 - experimental * @param the input and output value type * @since 2.2 */ @BackpressureSupport(BackpressureKind.FULL) @SchedulerSupport(SchedulerSupport.NONE) public final class MulticastProcessor<@NonNull T> extends FlowableProcessor { final AtomicInteger wip; final AtomicReference upstream; final AtomicReference[]> subscribers; final int bufferSize; final int limit; final boolean refcount; volatile SimpleQueue queue; volatile boolean done; volatile Throwable error; int consumed; int fusionMode; @SuppressWarnings("rawtypes") static final MulticastSubscription[] EMPTY = new MulticastSubscription[0]; @SuppressWarnings("rawtypes") static final MulticastSubscription[] TERMINATED = new MulticastSubscription[0]; /** * Constructs a fresh instance with the default Flowable.bufferSize() prefetch * amount and no refCount-behavior. * @param the input and output value type * @return the new MulticastProcessor instance */ @CheckReturnValue @NonNull public static MulticastProcessor create() { return new MulticastProcessor<>(bufferSize(), false); } /** * Constructs a fresh instance with the default Flowable.bufferSize() prefetch * amount and the optional refCount-behavior. * @param the input and output value type * @param refCount if true and if all Subscribers have canceled, the upstream * is cancelled * @return the new MulticastProcessor instance */ @CheckReturnValue @NonNull public static MulticastProcessor create(boolean refCount) { return new MulticastProcessor<>(bufferSize(), refCount); } /** * Constructs a fresh instance with the given prefetch amount and no refCount behavior. * @param bufferSize the prefetch amount * @param the input and output value type * @return the new MulticastProcessor instance * @throws IllegalArgumentException if {@code bufferSize} is non-positive */ @CheckReturnValue @NonNull public static MulticastProcessor create(int bufferSize) { ObjectHelper.verifyPositive(bufferSize, "bufferSize"); return new MulticastProcessor<>(bufferSize, false); } /** * Constructs a fresh instance with the given prefetch amount and the optional * refCount-behavior. * @param bufferSize the prefetch amount * @param refCount if true and if all Subscribers have canceled, the upstream * is cancelled * @param the input and output value type * @return the new MulticastProcessor instance * @throws IllegalArgumentException if {@code bufferSize} is non-positive */ @CheckReturnValue @NonNull public static MulticastProcessor create(int bufferSize, boolean refCount) { ObjectHelper.verifyPositive(bufferSize, "bufferSize"); return new MulticastProcessor<>(bufferSize, refCount); } /** * Constructs a fresh instance with the given prefetch amount and the optional * refCount-behavior. * @param bufferSize the prefetch amount * @param refCount if true and if all Subscribers have canceled, the upstream * is cancelled */ @SuppressWarnings("unchecked") MulticastProcessor(int bufferSize, boolean refCount) { this.bufferSize = bufferSize; this.limit = bufferSize - (bufferSize >> 2); this.wip = new AtomicInteger(); this.subscribers = new AtomicReference<>(EMPTY); this.upstream = new AtomicReference<>(); this.refcount = refCount; } /** * Initializes this Processor by setting an upstream Subscription that * ignores request amounts, uses a fixed buffer * and allows using the onXXX and offer methods * afterwards. */ public void start() { if (SubscriptionHelper.setOnce(upstream, EmptySubscription.INSTANCE)) { queue = new SpscArrayQueue<>(bufferSize); } } /** * Initializes this Processor by setting an upstream Subscription that * ignores request amounts, uses an unbounded buffer * and allows using the onXXX and offer methods * afterwards. */ public void startUnbounded() { if (SubscriptionHelper.setOnce(upstream, EmptySubscription.INSTANCE)) { queue = new SpscLinkedArrayQueue<>(bufferSize); } } @Override public void onSubscribe(@NonNull Subscription s) { if (SubscriptionHelper.setOnce(upstream, s)) { if (s instanceof QueueSubscription) { @SuppressWarnings("unchecked") QueueSubscription qs = (QueueSubscription)s; int m = qs.requestFusion(QueueSubscription.ANY); if (m == QueueSubscription.SYNC) { fusionMode = m; queue = qs; done = true; drain(); return; } if (m == QueueSubscription.ASYNC) { fusionMode = m; queue = qs; s.request(bufferSize); return; } } queue = new SpscArrayQueue<>(bufferSize); s.request(bufferSize); } } @Override public void onNext(@NonNull T t) { if (done) { return; } if (fusionMode == QueueSubscription.NONE) { ExceptionHelper.nullCheck(t, "onNext called with a null value."); if (!queue.offer(t)) { SubscriptionHelper.cancel(upstream); onError(MissingBackpressureException.createDefault()); return; } } drain(); } /** * Tries to offer an item into the internal queue and returns false * if the queue is full. * @param t the item to offer, not {@code null} * @return true if successful, false if the queue is full * @throws NullPointerException if {@code t} is {@code null} * @throws IllegalStateException if the processor is in fusion mode */ @CheckReturnValue public boolean offer(@NonNull T t) { ExceptionHelper.nullCheck(t, "offer called with a null value."); if (done) { return false; } if (fusionMode == QueueSubscription.NONE) { if (queue.offer(t)) { drain(); return true; } return false; } throw new IllegalStateException("offer() should not be called in fusion mode!"); } @Override public void onError(@NonNull Throwable t) { ExceptionHelper.nullCheck(t, "onError called with a null Throwable."); if (!done) { error = t; done = true; drain(); return; } RxJavaPlugins.onError(t); } @Override public void onComplete() { done = true; drain(); } @Override @CheckReturnValue public boolean hasSubscribers() { return subscribers.get().length != 0; } @Override @CheckReturnValue public boolean hasThrowable() { return done && error != null; } @Override @CheckReturnValue public boolean hasComplete() { return done && error == null; } @Override @CheckReturnValue public Throwable getThrowable() { return done ? error : null; } @Override protected void subscribeActual(@NonNull Subscriber s) { MulticastSubscription ms = new MulticastSubscription<>(s, this); s.onSubscribe(ms); if (add(ms)) { if (ms.get() == Long.MIN_VALUE) { remove(ms); } else { drain(); } } else { if (done) { Throwable ex = error; if (ex != null) { s.onError(ex); return; } } s.onComplete(); } } boolean add(MulticastSubscription inner) { for (;;) { MulticastSubscription[] a = subscribers.get(); if (a == TERMINATED) { return false; } int n = a.length; @SuppressWarnings("unchecked") MulticastSubscription[] b = new MulticastSubscription[n + 1]; System.arraycopy(a, 0, b, 0, n); b[n] = inner; if (subscribers.compareAndSet(a, b)) { return true; } } } @SuppressWarnings("unchecked") void remove(MulticastSubscription inner) { for (;;) { MulticastSubscription[] a = subscribers.get(); int n = a.length; if (n == 0) { return; } int j = -1; for (int i = 0; i < n; i++) { if (a[i] == inner) { j = i; break; } } if (j < 0) { break; } if (n == 1) { if (refcount) { if (subscribers.compareAndSet(a, TERMINATED)) { SubscriptionHelper.cancel(upstream); done = true; break; } } else { if (subscribers.compareAndSet(a, EMPTY)) { break; } } } else { MulticastSubscription[] b = new MulticastSubscription[n - 1]; System.arraycopy(a, 0, b, 0, j); System.arraycopy(a, j + 1, b, j, n - j - 1); if (subscribers.compareAndSet(a, b)) { break; } } } } @SuppressWarnings("unchecked") void drain() { if (wip.getAndIncrement() != 0) { return; } int missed = 1; AtomicReference[]> subs = subscribers; int c = consumed; int lim = limit; int fm = fusionMode; outer: for (;;) { SimpleQueue q = queue; if (q != null) { MulticastSubscription[] as = subs.get(); int n = as.length; if (n != 0) { long r = -1L; for (MulticastSubscription a : as) { long ra = a.get(); if (ra >= 0L) { if (r == -1L) { r = ra - a.emitted; } else { r = Math.min(r, ra - a.emitted); } } } while (r > 0L) { MulticastSubscription[] bs = subs.get(); if (bs == TERMINATED) { q.clear(); return; } if (as != bs) { continue outer; } boolean d = done; T v; try { v = q.poll(); } catch (Throwable ex) { Exceptions.throwIfFatal(ex); SubscriptionHelper.cancel(upstream); d = true; v = null; error = ex; done = true; } boolean empty = v == null; if (d && empty) { Throwable ex = error; if (ex != null) { for (MulticastSubscription inner : subs.getAndSet(TERMINATED)) { inner.onError(ex); } } else { for (MulticastSubscription inner : subs.getAndSet(TERMINATED)) { inner.onComplete(); } } return; } if (empty) { break; } for (MulticastSubscription inner : as) { inner.onNext(v); } r--; if (fm != QueueSubscription.SYNC) { if (++c == lim) { c = 0; upstream.get().request(lim); } } } if (r == 0) { MulticastSubscription[] bs = subs.get(); if (bs == TERMINATED) { q.clear(); return; } if (as != bs) { continue; } if (done && q.isEmpty()) { Throwable ex = error; if (ex != null) { for (MulticastSubscription inner : subs.getAndSet(TERMINATED)) { inner.onError(ex); } } else { for (MulticastSubscription inner : subs.getAndSet(TERMINATED)) { inner.onComplete(); } } return; } } } } consumed = c; missed = wip.addAndGet(-missed); if (missed == 0) { break; } } } static final class MulticastSubscription<@NonNull T> extends AtomicLong implements Subscription { private static final long serialVersionUID = -363282618957264509L; final Subscriber downstream; final MulticastProcessor parent; long emitted; MulticastSubscription(Subscriber actual, MulticastProcessor parent) { this.downstream = actual; this.parent = parent; } @Override public void request(long n) { if (SubscriptionHelper.validate(n)) { long r = BackpressureHelper.addCancel(this, n); if (r != Long.MIN_VALUE && r != Long.MAX_VALUE) { parent.drain(); } } } @Override public void cancel() { if (getAndSet(Long.MIN_VALUE) != Long.MIN_VALUE) { parent.remove(this); } } void onNext(T t) { if (get() != Long.MIN_VALUE) { emitted++; downstream.onNext(t); } } void onError(Throwable t) { if (get() != Long.MIN_VALUE) { downstream.onError(t); } } void onComplete() { if (get() != Long.MIN_VALUE) { downstream.onComplete(); } } } }





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