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.flowable;

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

import org.reactivestreams.*;

import io.reactivex.Flowable;
import io.reactivex.disposables.CompositeDisposable;
import io.reactivex.exceptions.*;
import io.reactivex.functions.*;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.SimpleQueue;
import io.reactivex.internal.operators.flowable.FlowableGroupJoin.*;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.*;
import io.reactivex.plugins.RxJavaPlugins;

public final class FlowableJoin<TLeft, TRight, TLeftEnd, TRightEnd, R> extends AbstractFlowableWithUpstream<TLeft, R> {

    final Publisher<? extends TRight> other;

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

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

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

    public FlowableJoin(
            Flowable<TLeft> source,
            Publisher<? extends TRight> other,
            Function<? super TLeft, ? extends Publisher<TLeftEnd>> leftEnd,
            Function<? super TRight, ? extends Publisher<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(Subscriber<? super R> s) {

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

        s.onSubscribe(parent);

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

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

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

        private static final long serialVersionUID = -6071216598687999801L;

        final Subscriber<? super R> downstream;

        final AtomicLong requested;

        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 Publisher<TLeftEnd>> leftEnd;

        final Function<? super TRight, ? extends Publisher<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;

        JoinSubscription(Subscriber<? super R> actual, Function<? super TLeft, ? extends Publisher<TLeftEnd>> leftEnd,
                Function<? super TRight, ? extends Publisher<TRightEnd>> rightEnd,
                        BiFunction<? super TLeft, ? super TRight, ? extends R> resultSelector) {
            this.downstream = actual;
            this.requested = new AtomicLong();
            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 request(long n) {
            if (SubscriptionHelper.validate(n)) {
                BackpressureHelper.add(requested, n);
            }
        }

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

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

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

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

            a.onError(ex);
        }

        void fail(Throwable exc, Subscriber<?> a, SimpleQueue<?> 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;
            Subscriber<? 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);

                        Publisher<TLeftEnd> p;

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

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

                        p.subscribe(end);

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

                        long r = requested.get();
                        long e = 0L;

                        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;
                            }

                            if (e != r) {
                                a.onNext(w);

                                e++;
                            } else {
                                ExceptionHelper.addThrowable(error, new MissingBackpressureException("Could not emit value due to lack of requests"));
                                q.clear();
                                cancelAll();
                                errorAll(a);
                                return;
                            }
                        }

                        if (e != 0L) {
                            BackpressureHelper.produced(requested, e);
                        }
                    }
                    else if (mode == RIGHT_VALUE) {
                        @SuppressWarnings("unchecked")
                        TRight right = (TRight)val;

                        int idx = rightIndex++;

                        rights.put(idx, right);

                        Publisher<TRightEnd> p;

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

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

                        p.subscribe(end);

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

                        long r = requested.get();
                        long e = 0L;

                        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;
                            }

                            if (e != r) {
                                a.onNext(w);

                                e++;
                            } else {
                                ExceptionHelper.addThrowable(error, new MissingBackpressureException("Could not emit value due to lack of requests"));
                                q.clear();
                                cancelAll();
                                errorAll(a);
                                return;
                            }
                        }

                        if (e != 0L) {
                            BackpressureHelper.produced(requested, e);
                        }
                    }
                    else if (mode == LEFT_CLOSE) {
                        LeftRightEndSubscriber end = (LeftRightEndSubscriber)val;

                        lefts.remove(end.index);
                        disposables.remove(end);
                    }
                    else if (mode == RIGHT_CLOSE) {
                        LeftRightEndSubscriber end = (LeftRightEndSubscriber)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(LeftRightSubscriber 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, LeftRightEndSubscriber 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);
            }
        }
    }
}