ObservableWindowBoundarySupplier.java

/**
 * 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.internal.operators.observable;

import java.util.concurrent.Callable;
import java.util.concurrent.atomic.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.queue.MpscLinkedQueue;
import io.reactivex.internal.util.AtomicThrowable;
import io.reactivex.observers.DisposableObserver;
import io.reactivex.plugins.RxJavaPlugins;
import io.reactivex.subjects.UnicastSubject;

public final class ObservableWindowBoundarySupplier<T, B> extends AbstractObservableWithUpstream<T, Observable<T>> {
    final Callable<? extends ObservableSource<B>> other;
    final int capacityHint;

    public ObservableWindowBoundarySupplier(
            ObservableSource<T> source,
            Callable<? extends ObservableSource<B>> other, int capacityHint) {
        super(source);
        this.other = other;
        this.capacityHint = capacityHint;
    }

    @Override
    public void subscribeActual(Observer<? super Observable<T>> observer) {
        WindowBoundaryMainObserver<T, B> parent = new WindowBoundaryMainObserver<T, B>(observer, capacityHint, other);

        source.subscribe(parent);
    }

    static final class WindowBoundaryMainObserver<T, B>
    extends AtomicInteger
    implements Observer<T>, Disposable, Runnable {

        private static final long serialVersionUID = 2233020065421370272L;

        final Observer<? super Observable<T>> downstream;

        final int capacityHint;

        final AtomicReference<WindowBoundaryInnerObserver<T, B>> boundaryObserver;

        static final WindowBoundaryInnerObserver<Object, Object> BOUNDARY_DISPOSED = new WindowBoundaryInnerObserver<Object, Object>(null);

        final AtomicInteger windows;

        final MpscLinkedQueue<Object> queue;

        final AtomicThrowable errors;

        final AtomicBoolean stopWindows;

        final Callable<? extends ObservableSource<B>> other;

        static final Object NEXT_WINDOW = new Object();

        Disposable upstream;

        volatile boolean done;

        UnicastSubject<T> window;

        WindowBoundaryMainObserver(Observer<? super Observable<T>> downstream, int capacityHint, Callable<? extends ObservableSource<B>> other) {
            this.downstream = downstream;
            this.capacityHint = capacityHint;
            this.boundaryObserver = new AtomicReference<WindowBoundaryInnerObserver<T, B>>();
            this.windows = new AtomicInteger(1);
            this.queue = new MpscLinkedQueue<Object>();
            this.errors = new AtomicThrowable();
            this.stopWindows = new AtomicBoolean();
            this.other = other;
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(upstream, d)) {
                upstream = d;
                downstream.onSubscribe(this);
                queue.offer(NEXT_WINDOW);
                drain();
            }
        }

        @Override
        public void onNext(T t) {
            queue.offer(t);
            drain();
        }

        @Override
        public void onError(Throwable e) {
            disposeBoundary();
            if (errors.addThrowable(e)) {
                done = true;
                drain();
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        @Override
        public void onComplete() {
            disposeBoundary();
            done = true;
            drain();
        }

        @Override
        public void dispose() {
            if (stopWindows.compareAndSet(false, true)) {
                disposeBoundary();
                if (windows.decrementAndGet() == 0) {
                    upstream.dispose();
                }
            }
        }

        @SuppressWarnings({ "rawtypes", "unchecked" })
        void disposeBoundary() {
            Disposable d = boundaryObserver.getAndSet((WindowBoundaryInnerObserver)BOUNDARY_DISPOSED);
            if (d != null && d != BOUNDARY_DISPOSED) {
                d.dispose();
            }
        }

        @Override
        public boolean isDisposed() {
            return stopWindows.get();
        }

        @Override
        public void run() {
            if (windows.decrementAndGet() == 0) {
                upstream.dispose();
            }
        }

        void innerNext(WindowBoundaryInnerObserver<T, B> sender) {
            boundaryObserver.compareAndSet(sender, null);
            queue.offer(NEXT_WINDOW);
            drain();
        }

        void innerError(Throwable e) {
            upstream.dispose();
            if (errors.addThrowable(e)) {
                done = true;
                drain();
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        void innerComplete() {
            upstream.dispose();
            done = true;
            drain();
        }

        @SuppressWarnings("unchecked")
        void drain() {
            if (getAndIncrement() != 0) {
                return;
            }

            int missed = 1;
            Observer<? super Observable<T>> downstream = this.downstream;
            MpscLinkedQueue<Object> queue = this.queue;
            AtomicThrowable errors = this.errors;

            for (;;) {

                for (;;) {
                    if (windows.get() == 0) {
                        queue.clear();
                        window = null;
                        return;
                    }

                    UnicastSubject<T> w = window;

                    boolean d = done;

                    if (d && errors.get() != null) {
                        queue.clear();
                        Throwable ex = errors.terminate();
                        if (w != null) {
                            window = null;
                            w.onError(ex);
                        }
                        downstream.onError(ex);
                        return;
                    }

                    Object v = queue.poll();

                    boolean empty = v == null;

                    if (d && empty) {
                        Throwable ex = errors.terminate();
                        if (ex == null) {
                            if (w != null) {
                                window = null;
                                w.onComplete();
                            }
                            downstream.onComplete();
                        } else {
                            if (w != null) {
                                window = null;
                                w.onError(ex);
                            }
                            downstream.onError(ex);
                        }
                        return;
                    }

                    if (empty) {
                        break;
                    }

                    if (v != NEXT_WINDOW) {
                        w.onNext((T)v);
                        continue;
                    }

                    if (w != null) {
                        window = null;
                        w.onComplete();
                    }

                    if (!stopWindows.get()) {
                        w = UnicastSubject.create(capacityHint, this);
                        window = w;
                        windows.getAndIncrement();

                        ObservableSource<B> otherSource;

                        try {
                            otherSource = ObjectHelper.requireNonNull(other.call(), "The other Callable returned a null ObservableSource");
                        } catch (Throwable ex) {
                            Exceptions.throwIfFatal(ex);
                            errors.addThrowable(ex);
                            done = true;
                            continue;
                        }

                        WindowBoundaryInnerObserver<T, B> bo = new WindowBoundaryInnerObserver<T, B>(this);

                        if (boundaryObserver.compareAndSet(null, bo)) {
                            otherSource.subscribe(bo);

                            downstream.onNext(w);
                        }
                    }
                }

                missed = addAndGet(-missed);
                if (missed == 0) {
                    break;
                }
            }
        }
    }

    static final class WindowBoundaryInnerObserver<T, B> extends DisposableObserver<B> {
        final WindowBoundaryMainObserver<T, B> parent;

        boolean done;

        WindowBoundaryInnerObserver(WindowBoundaryMainObserver<T, B> parent) {
            this.parent = parent;
        }

        @Override
        public void onNext(B t) {
            if (done) {
                return;
            }
            done = true;
            dispose();
            parent.innerNext(this);
        }

        @Override
        public void onError(Throwable t) {
            if (done) {
                RxJavaPlugins.onError(t);
                return;
            }
            done = true;
            parent.innerError(t);
        }

        @Override
        public void onComplete() {
            if (done) {
                return;
            }
            done = true;
            parent.innerComplete();
        }
    }
}