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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.observers;

import io.reactivex.Observer;
import io.reactivex.annotations.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.util.*;
import io.reactivex.plugins.RxJavaPlugins;

/**
 * Serializes access to the onNext, onError and onComplete methods of another Observer.
 *
 * 

Note that {@link #onSubscribe(Disposable)} is not serialized in respect of the other methods so * make sure the {@code onSubscribe()} is called with a non-null {@code Disposable} * before any of the other methods are called. * *

The implementation assumes that the actual Observer's methods don't throw. * * @param the value type */ public final class SerializedObserver implements Observer, Disposable { final Observer downstream; final boolean delayError; static final int QUEUE_LINK_SIZE = 4; Disposable upstream; boolean emitting; AppendOnlyLinkedArrayList queue; volatile boolean done; /** * Construct a SerializedObserver by wrapping the given actual Observer. * @param downstream the actual Observer, not null (not verified) */ public SerializedObserver(@NonNull Observer downstream) { this(downstream, false); } /** * Construct a SerializedObserver by wrapping the given actual Observer and * optionally delaying the errors till all regular values have been emitted * from the internal buffer. * @param actual the actual Observer, not null (not verified) * @param delayError if true, errors are emitted after regular values have been emitted */ public SerializedObserver(@NonNull Observer actual, boolean delayError) { this.downstream = actual; this.delayError = delayError; } @Override public void onSubscribe(@NonNull Disposable d) { if (DisposableHelper.validate(this.upstream, d)) { this.upstream = d; downstream.onSubscribe(this); } } @Override public void dispose() { upstream.dispose(); } @Override public boolean isDisposed() { return upstream.isDisposed(); } @Override public void onNext(@NonNull T t) { if (done) { return; } if (t == null) { upstream.dispose(); onError(new NullPointerException("onNext called with null. Null values are generally not allowed in 2.x operators and sources.")); return; } synchronized (this) { if (done) { return; } if (emitting) { AppendOnlyLinkedArrayList q = queue; if (q == null) { q = new AppendOnlyLinkedArrayList(QUEUE_LINK_SIZE); queue = q; } q.add(NotificationLite.next(t)); return; } emitting = true; } downstream.onNext(t); emitLoop(); } @Override public void onError(@NonNull Throwable t) { if (done) { RxJavaPlugins.onError(t); return; } boolean reportError; synchronized (this) { if (done) { reportError = true; } else if (emitting) { done = true; AppendOnlyLinkedArrayList q = queue; if (q == null) { q = new AppendOnlyLinkedArrayList(QUEUE_LINK_SIZE); queue = q; } Object err = NotificationLite.error(t); if (delayError) { q.add(err); } else { q.setFirst(err); } return; } else { done = true; emitting = true; reportError = false; } } if (reportError) { RxJavaPlugins.onError(t); return; } downstream.onError(t); // no need to loop because this onError is the last event } @Override public void onComplete() { if (done) { return; } synchronized (this) { if (done) { return; } if (emitting) { AppendOnlyLinkedArrayList q = queue; if (q == null) { q = new AppendOnlyLinkedArrayList(QUEUE_LINK_SIZE); queue = q; } q.add(NotificationLite.complete()); return; } done = true; emitting = true; } downstream.onComplete(); // no need to loop because this onComplete is the last event } void emitLoop() { for (;;) { AppendOnlyLinkedArrayList q; synchronized (this) { q = queue; if (q == null) { emitting = false; return; } queue = null; } if (q.accept(downstream)) { return; } } } }