https://github.com/ReactiveX/RxJava: Reactive Extensions for Java
  • David Karnok 
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.

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

import io.reactivex.ObservableSource;
import io.reactivex.Observer;
import io.reactivex.disposables.*;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.*;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.operators.observable.ObservableGroupJoin.*;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.internal.util.ExceptionHelper;
import io.reactivex.plugins.RxJavaPlugins;

public final class ObservableJoin<TLeft, TRight, TLeftEnd, TRightEnd, R> extends AbstractObservableWithUpstream<TLeft, R> {

    final ObservableSource<? extends TRight> other;

    final Function<? super TLeft, ? extends ObservableSource<TLeftEnd>> leftEnd;

    final Function<? super TRight, ? extends ObservableSource<TRightEnd>> rightEnd;

    final BiFunction<? super TLeft, ? super TRight, ? extends R> resultSelector;

    public ObservableJoin(
            ObservableSource<TLeft> source,
            ObservableSource<? extends TRight> other,
            Function<? super TLeft, ? extends ObservableSource<TLeftEnd>> leftEnd,
            Function<? super TRight, ? extends ObservableSource<TRightEnd>> rightEnd,
            BiFunction<? super TLeft, ? super TRight, ? extends R> resultSelector) {
        super(source);
        this.other = other;
        this.leftEnd = leftEnd;
        this.rightEnd = rightEnd;
        this.resultSelector = resultSelector;
    }

    @Override
    protected void subscribeActual(Observer<? super R> observer) {

        JoinDisposable<TLeft, TRight, TLeftEnd, TRightEnd, R> parent =
                new JoinDisposable<TLeft, TRight, TLeftEnd, TRightEnd, R>(
                        observer, leftEnd, rightEnd, resultSelector);

        observer.onSubscribe(parent);

        LeftRightObserver left = new LeftRightObserver(parent, true);
        parent.disposables.add(left);
        LeftRightObserver right = new LeftRightObserver(parent, false);
        parent.disposables.add(right);

        source.subscribe(left);
        other.subscribe(right);
    }

    static final class JoinDisposable<TLeft, TRight, TLeftEnd, TRightEnd, R>
    extends AtomicInteger implements Disposable, JoinSupport {

        private static final long serialVersionUID = -6071216598687999801L;

        final Observer<? super R> downstream;

        final SpscLinkedArrayQueue<Object> queue;

        final CompositeDisposable disposables;

        final Map<Integer, TLeft> lefts;

        final Map<Integer, TRight> rights;

        final AtomicReference<Throwable> error;

        final Function<? super TLeft, ? extends ObservableSource<TLeftEnd>> leftEnd;

        final Function<? super TRight, ? extends ObservableSource<TRightEnd>> rightEnd;

        final BiFunction<? super TLeft, ? super TRight, ? extends R> resultSelector;

        final AtomicInteger active;

        int leftIndex;

        int rightIndex;

        volatile boolean cancelled;

        static final Integer LEFT_VALUE = 1;

        static final Integer RIGHT_VALUE = 2;

        static final Integer LEFT_CLOSE = 3;

        static final Integer RIGHT_CLOSE = 4;

        JoinDisposable(Observer<? super R> actual,
                Function<? super TLeft, ? extends ObservableSource<TLeftEnd>> leftEnd,
                Function<? super TRight, ? extends ObservableSource<TRightEnd>> rightEnd,
                        BiFunction<? super TLeft, ? super TRight, ? extends R> resultSelector) {
            this.downstream = actual;
            this.disposables = new CompositeDisposable();
            this.queue = new SpscLinkedArrayQueue<Object>(bufferSize());
            this.lefts = new LinkedHashMap<Integer, TLeft>();
            this.rights = new LinkedHashMap<Integer, TRight>();
            this.error = new AtomicReference<Throwable>();
            this.leftEnd = leftEnd;
            this.rightEnd = rightEnd;
            this.resultSelector = resultSelector;
            this.active = new AtomicInteger(2);
        }

        @Override
        public void dispose() {
            if (!cancelled) {
                cancelled = true;
                cancelAll();
                if (getAndIncrement() == 0) {
                    queue.clear();
                }
            }
        }

        @Override
        public boolean isDisposed() {
            return cancelled;
        }

        void cancelAll() {
            disposables.dispose();
        }

        void errorAll(Observer<?> a) {
            Throwable ex = ExceptionHelper.terminate(error);

            lefts.clear();
            rights.clear();

            a.onError(ex);
        }

        void fail(Throwable exc, Observer<?> a, SpscLinkedArrayQueue<?> q) {
            Exceptions.throwIfFatal(exc);
            ExceptionHelper.addThrowable(error, exc);
            q.clear();
            cancelAll();
            errorAll(a);
        }

        void drain() {
            if (getAndIncrement() != 0) {
                return;
            }

            int missed = 1;
            SpscLinkedArrayQueue<Object> q = queue;
            Observer<? super R> a = downstream;

            for (;;) {
                for (;;) {
                    if (cancelled) {
                        q.clear();
                        return;
                    }

                    Throwable ex = error.get();
                    if (ex != null) {
                        q.clear();
                        cancelAll();
                        errorAll(a);
                        return;
                    }

                    boolean d = active.get() == 0;

                    Integer mode = (Integer)q.poll();

                    boolean empty = mode == null;

                    if (d && empty) {

                        lefts.clear();
                        rights.clear();
                        disposables.dispose();

                        a.onComplete();
                        return;
                    }

                    if (empty) {
                        break;
                    }

                    Object val = q.poll();

                    if (mode == LEFT_VALUE) {
                        @SuppressWarnings("unchecked")
                        TLeft left = (TLeft)val;

                        int idx = leftIndex++;
                        lefts.put(idx, left);

                        ObservableSource<TLeftEnd> p;

                        try {
                            p = ObjectHelper.requireNonNull(leftEnd.apply(left), "The leftEnd returned a null ObservableSource");
                        } catch (Throwable exc) {
                            fail(exc, a, q);
                            return;
                        }

                        LeftRightEndObserver end = new LeftRightEndObserver(this, true, idx);
                        disposables.add(end);

                        p.subscribe(end);

                        ex = error.get();
                        if (ex != null) {
                            q.clear();
                            cancelAll();
                            errorAll(a);
                            return;
                        }

                        for (TRight right : rights.values()) {

                            R w;

                            try {
                                w = ObjectHelper.requireNonNull(resultSelector.apply(left, right), "The resultSelector returned a null value");
                            } catch (Throwable exc) {
                                fail(exc, a, q);
                                return;
                            }

                            a.onNext(w);
                        }
                    }
                    else if (mode == RIGHT_VALUE) {
                        @SuppressWarnings("unchecked")
                        TRight right = (TRight)val;

                        int idx = rightIndex++;

                        rights.put(idx, right);

                        ObservableSource<TRightEnd> p;

                        try {
                            p = ObjectHelper.requireNonNull(rightEnd.apply(right), "The rightEnd returned a null ObservableSource");
                        } catch (Throwable exc) {
                            fail(exc, a, q);
                            return;
                        }

                        LeftRightEndObserver end = new LeftRightEndObserver(this, false, idx);
                        disposables.add(end);

                        p.subscribe(end);

                        ex = error.get();
                        if (ex != null) {
                            q.clear();
                            cancelAll();
                            errorAll(a);
                            return;
                        }

                        for (TLeft left : lefts.values()) {

                            R w;

                            try {
                                w = ObjectHelper.requireNonNull(resultSelector.apply(left, right), "The resultSelector returned a null value");
                            } catch (Throwable exc) {
                                fail(exc, a, q);
                                return;
                            }

                            a.onNext(w);
                        }
                    }
                    else if (mode == LEFT_CLOSE) {
                        LeftRightEndObserver end = (LeftRightEndObserver)val;

                        lefts.remove(end.index);
                        disposables.remove(end);
                    } else {
                        LeftRightEndObserver end = (LeftRightEndObserver)val;

                        rights.remove(end.index);
                        disposables.remove(end);
                    }
                }

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

        @Override
        public void innerError(Throwable ex) {
            if (ExceptionHelper.addThrowable(error, ex)) {
                active.decrementAndGet();
                drain();
            } else {
                RxJavaPlugins.onError(ex);
            }
        }

        @Override
        public void innerComplete(LeftRightObserver sender) {
            disposables.delete(sender);
            active.decrementAndGet();
            drain();
        }

        @Override
        public void innerValue(boolean isLeft, Object o) {
            synchronized (this) {
                queue.offer(isLeft ? LEFT_VALUE : RIGHT_VALUE, o);
            }
            drain();
        }

        @Override
        public void innerClose(boolean isLeft, LeftRightEndObserver index) {
            synchronized (this) {
                queue.offer(isLeft ? LEFT_CLOSE : RIGHT_CLOSE, index);
            }
            drain();
        }

        @Override
        public void innerCloseError(Throwable ex) {
            if (ExceptionHelper.addThrowable(error, ex)) {
                drain();
            } else {
                RxJavaPlugins.onError(ex);
            }
        }
    }
}