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

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.*;
import io.reactivex.internal.queue.SpscArrayQueue;
import io.reactivex.internal.subscriptions.*;
import io.reactivex.internal.util.*;
import io.reactivex.plugins.RxJavaPlugins;

public final class FlowableZip<T, R> extends Flowable<R> {

    final Publisher<? extends T>[] sources;
    final Iterable<? extends Publisher<? extends T>> sourcesIterable;
    final Function<? super Object[], ? extends R> zipper;
    final int bufferSize;
    final boolean delayError;

    public FlowableZip(Publisher<? extends T>[] sources,
            Iterable<? extends Publisher<? extends T>> sourcesIterable,
                    Function<? super Object[], ? extends R> zipper,
                    int bufferSize,
                    boolean delayError) {
        this.sources = sources;
        this.sourcesIterable = sourcesIterable;
        this.zipper = zipper;
        this.bufferSize = bufferSize;
        this.delayError = delayError;
    }

    @Override
    @SuppressWarnings("unchecked")
    public void subscribeActual(Subscriber<? super R> s) {
        Publisher<? extends T>[] sources = this.sources;
        int count = 0;
        if (sources == null) {
            sources = new Publisher[8];
            for (Publisher<? extends T> p : sourcesIterable) {
                if (count == sources.length) {
                    Publisher<? extends T>[] b = new Publisher[count + (count >> 2)];
                    System.arraycopy(sources, 0, b, 0, count);
                    sources = b;
                }
                sources[count++] = p;
            }
        } else {
            count = sources.length;
        }

        if (count == 0) {
            EmptySubscription.complete(s);
            return;
        }

        ZipCoordinator<T, R> coordinator = new ZipCoordinator<T, R>(s, zipper, count, bufferSize, delayError);

        s.onSubscribe(coordinator);

        coordinator.subscribe(sources, count);
    }

    static final class ZipCoordinator<T, R>
    extends AtomicInteger
    implements Subscription {

        private static final long serialVersionUID = -2434867452883857743L;

        final Subscriber<? super R> downstream;

        final ZipSubscriber<T, R>[] subscribers;

        final Function<? super Object[], ? extends R> zipper;

        final AtomicLong requested;

        final AtomicThrowable errors;

        final boolean delayErrors;

        volatile boolean cancelled;

        final Object[] current;

        ZipCoordinator(Subscriber<? super R> actual,
                Function<? super Object[], ? extends R> zipper, int n, int prefetch, boolean delayErrors) {
            this.downstream = actual;
            this.zipper = zipper;
            this.delayErrors = delayErrors;
            @SuppressWarnings("unchecked")
            ZipSubscriber<T, R>[] a = new ZipSubscriber[n];
            for (int i = 0; i < n; i++) {
                a[i] = new ZipSubscriber<T, R>(this, prefetch);
            }
            this.current = new Object[n];
            this.subscribers = a;
            this.requested = new AtomicLong();
            this.errors = new AtomicThrowable();
        }

        void subscribe(Publisher<? extends T>[] sources, int n) {
            ZipSubscriber<T, R>[] a = subscribers;
            for (int i = 0; i < n; i++) {
                if (cancelled || (!delayErrors && errors.get() != null)) {
                    return;
                }
                sources[i].subscribe(a[i]);
            }
        }

        @Override
        public void request(long n) {
            if (SubscriptionHelper.validate(n)) {
                BackpressureHelper.add(requested, n);
                drain();
            }
        }

        @Override
        public void cancel() {
            if (!cancelled) {
                cancelled = true;

                cancelAll();
            }
        }

        void error(ZipSubscriber<T, R> inner, Throwable e) {
            if (errors.addThrowable(e)) {
                inner.done = true;
                drain();
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        void cancelAll() {
            for (ZipSubscriber<T, R> s : subscribers) {
                s.cancel();
            }
        }

        void drain() {

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

            final Subscriber<? super R> a = downstream;
            final ZipSubscriber<T, R>[] qs = subscribers;
            final int n = qs.length;
            Object[] values = current;

            int missed = 1;

            for (;;) {

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

                while (r != e) {

                    if (cancelled) {
                        return;
                    }

                    if (!delayErrors && errors.get() != null) {
                        cancelAll();
                        a.onError(errors.terminate());
                        return;
                    }

                    boolean empty = false;

                    for (int j = 0; j < n; j++) {
                        ZipSubscriber<T, R> inner = qs[j];
                        if (values[j] == null) {
                            try {
                                boolean d = inner.done;
                                SimpleQueue<T> q = inner.queue;

                                T v = q != null ? q.poll() : null;

                                boolean sourceEmpty = v == null;
                                if (d && sourceEmpty) {
                                    cancelAll();
                                    Throwable ex = errors.get();
                                    if (ex != null) {
                                        a.onError(errors.terminate());
                                    } else {
                                        a.onComplete();
                                    }
                                    return;
                                }
                                if (!sourceEmpty) {
                                    values[j] = v;
                                } else {
                                    empty = true;
                                }
                            } catch (Throwable ex) {
                                Exceptions.throwIfFatal(ex);

                                errors.addThrowable(ex);
                                if (!delayErrors) {
                                    cancelAll();
                                    a.onError(errors.terminate());
                                    return;
                                }
                                empty = true;
                            }
                        }
                    }

                    if (empty) {
                        break;
                    }

                    R v;

                    try {
                        v = ObjectHelper.requireNonNull(zipper.apply(values.clone()), "The zipper returned a null value");
                    } catch (Throwable ex) {
                        Exceptions.throwIfFatal(ex);
                        cancelAll();
                        errors.addThrowable(ex);
                        a.onError(errors.terminate());
                        return;
                    }

                    a.onNext(v);

                    e++;

                    Arrays.fill(values, null);
                }

                if (r == e) {
                    if (cancelled) {
                        return;
                    }

                    if (!delayErrors && errors.get() != null) {
                        cancelAll();
                        a.onError(errors.terminate());
                        return;
                    }

                    for (int j = 0; j < n; j++) {
                        ZipSubscriber<T, R> inner = qs[j];
                        if (values[j] == null) {
                            try {
                                boolean d = inner.done;
                                SimpleQueue<T> q = inner.queue;
                                T v = q != null ? q.poll() : null;

                                boolean empty = v == null;
                                if (d && empty) {
                                    cancelAll();
                                    Throwable ex = errors.get();
                                    if (ex != null) {
                                        a.onError(errors.terminate());
                                    } else {
                                        a.onComplete();
                                    }
                                    return;
                                }
                                if (!empty) {
                                    values[j] = v;
                                }
                            } catch (Throwable ex) {
                                Exceptions.throwIfFatal(ex);
                                errors.addThrowable(ex);
                                if (!delayErrors) {
                                    cancelAll();
                                    a.onError(errors.terminate());
                                    return;
                                }
                            }
                        }
                    }

                }

                if (e != 0L) {

                    for (ZipSubscriber<T, R> inner : qs) {
                        inner.request(e);
                    }

                    if (r != Long.MAX_VALUE) {
                        requested.addAndGet(-e);
                    }
                }

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

    static final class ZipSubscriber<T, R> extends AtomicReference<Subscription> implements FlowableSubscriber<T>, Subscription {

        private static final long serialVersionUID = -4627193790118206028L;

        final ZipCoordinator<T, R> parent;

        final int prefetch;

        final int limit;

        SimpleQueue<T> queue;

        long produced;

        volatile boolean done;

        int sourceMode;

        ZipSubscriber(ZipCoordinator<T, R> parent, int prefetch) {
            this.parent = parent;
            this.prefetch = prefetch;
            this.limit = prefetch - (prefetch >> 2);
        }

        @SuppressWarnings("unchecked")
        @Override
        public void onSubscribe(Subscription s) {
            if (SubscriptionHelper.setOnce(this, s)) {
                if (s instanceof QueueSubscription) {
                    QueueSubscription<T> f = (QueueSubscription<T>) s;

                    int m = f.requestFusion(QueueSubscription.ANY | QueueSubscription.BOUNDARY);

                    if (m == QueueSubscription.SYNC) {
                        sourceMode = m;
                        queue = f;
                        done = true;
                        parent.drain();
                        return;
                    }
                    if (m == QueueSubscription.ASYNC) {
                        sourceMode = m;
                        queue = f;
                        s.request(prefetch);
                        return;
                    }
                }

                queue = new SpscArrayQueue<T>(prefetch);

                s.request(prefetch);
            }
        }

        @Override
        public void onNext(T t) {
            if (sourceMode != QueueSubscription.ASYNC) {
                queue.offer(t);
            }
            parent.drain();
        }

        @Override
        public void onError(Throwable t) {
            parent.error(this, t);
        }

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

        @Override
        public void cancel() {
            SubscriptionHelper.cancel(this);
        }

        @Override
        public void request(long n) {
            if (sourceMode != QueueSubscription.SYNC) {
                long p = produced + n;
                if (p >= limit) {
                    produced = 0L;
                    get().request(p);
                } else {
                    produced = p;
                }
            }
        }
    }
}