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.concurrent.atomic.*;

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.exceptions.*;
import io.reactivex.functions.Function;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.SimpleQueue;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.internal.subscribers.*;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.*;
import io.reactivex.plugins.RxJavaPlugins;

public final class FlowableConcatMapEager<T, R> extends AbstractFlowableWithUpstream<T, R> {

    final Function<? super T, ? extends Publisher<? extends R>> mapper;

    final int maxConcurrency;

    final int prefetch;

    final ErrorMode errorMode;

    public FlowableConcatMapEager(Flowable<T> source,
            Function<? super T, ? extends Publisher<? extends R>> mapper,
            int maxConcurrency,
            int prefetch,
            ErrorMode errorMode) {
        super(source);
        this.mapper = mapper;
        this.maxConcurrency = maxConcurrency;
        this.prefetch = prefetch;
        this.errorMode = errorMode;
    }

    @Override
    protected void subscribeActual(Subscriber<? super R> s) {
        source.subscribe(new ConcatMapEagerDelayErrorSubscriber<T, R>(
                s, mapper, maxConcurrency, prefetch, errorMode));
    }

    static final class ConcatMapEagerDelayErrorSubscriber<T, R>
    extends AtomicInteger
    implements FlowableSubscriber<T>, Subscription, InnerQueuedSubscriberSupport<R> {

        private static final long serialVersionUID = -4255299542215038287L;

        final Subscriber<? super R> downstream;

        final Function<? super T, ? extends Publisher<? extends R>> mapper;

        final int maxConcurrency;

        final int prefetch;

        final ErrorMode errorMode;

        final AtomicThrowable errors;

        final AtomicLong requested;

        final SpscLinkedArrayQueue<InnerQueuedSubscriber<R>> subscribers;

        Subscription upstream;

        volatile boolean cancelled;

        volatile boolean done;

        volatile InnerQueuedSubscriber<R> current;

        ConcatMapEagerDelayErrorSubscriber(Subscriber<? super R> actual,
                Function<? super T, ? extends Publisher<? extends R>> mapper, int maxConcurrency, int prefetch,
                ErrorMode errorMode) {
            this.downstream = actual;
            this.mapper = mapper;
            this.maxConcurrency = maxConcurrency;
            this.prefetch = prefetch;
            this.errorMode = errorMode;
            this.subscribers = new SpscLinkedArrayQueue<InnerQueuedSubscriber<R>>(Math.min(prefetch, maxConcurrency));
            this.errors = new AtomicThrowable();
            this.requested = new AtomicLong();
        }

        @Override
        public void onSubscribe(Subscription s) {
            if (SubscriptionHelper.validate(this.upstream, s)) {
                this.upstream = s;

                downstream.onSubscribe(this);

                s.request(maxConcurrency == Integer.MAX_VALUE ? Long.MAX_VALUE : maxConcurrency);
            }

        }

        @Override
        public void onNext(T t) {
            Publisher<? extends R> p;

            try {
                p = ObjectHelper.requireNonNull(mapper.apply(t), "The mapper returned a null Publisher");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                upstream.cancel();
                onError(ex);
                return;
            }

            InnerQueuedSubscriber<R> inner = new InnerQueuedSubscriber<R>(this, prefetch);

            if (cancelled) {
                return;
            }

            subscribers.offer(inner);

            p.subscribe(inner);

            if (cancelled) {
                inner.cancel();
                drainAndCancel();
            }
        }

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

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

        @Override
        public void cancel() {
            if (cancelled) {
                return;
            }
            cancelled = true;
            upstream.cancel();

            drainAndCancel();
        }

        void drainAndCancel() {
            if (getAndIncrement() == 0) {
                do {
                    cancelAll();
                } while (decrementAndGet() != 0);
            }
        }

        void cancelAll() {
            InnerQueuedSubscriber<R> inner = current;
            current = null;

            if (inner != null) {
                inner.cancel();
            }

            while ((inner = subscribers.poll()) != null) {
                inner.cancel();
            }
        }

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

        @Override
        public void innerNext(InnerQueuedSubscriber<R> inner, R value) {
            if (inner.queue().offer(value)) {
                drain();
            } else {
                inner.cancel();
                innerError(inner, new MissingBackpressureException());
            }
        }

        @Override
        public void innerError(InnerQueuedSubscriber<R> inner, Throwable e) {
            if (errors.addThrowable(e)) {
                inner.setDone();
                if (errorMode != ErrorMode.END) {
                    upstream.cancel();
                }
                drain();
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        @Override
        public void innerComplete(InnerQueuedSubscriber<R> inner) {
            inner.setDone();
            drain();
        }

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

            int missed = 1;
            InnerQueuedSubscriber<R> inner = current;
            Subscriber<? super R> a = downstream;
            ErrorMode em = errorMode;

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

                if (inner == null) {

                    if (em != ErrorMode.END) {
                        Throwable ex = errors.get();
                        if (ex != null) {
                            cancelAll();

                            a.onError(errors.terminate());
                            return;
                        }
                    }

                    boolean outerDone = done;

                    inner = subscribers.poll();

                    if (outerDone && inner == null) {
                        Throwable ex = errors.terminate();
                        if (ex != null) {
                            a.onError(ex);
                        } else {
                            a.onComplete();
                        }
                        return;
                    }

                    if (inner != null) {
                        current = inner;
                    }
                }

                boolean continueNextSource = false;

                if (inner != null) {
                    SimpleQueue<R> q = inner.queue();
                    if (q != null) {
                        while (e != r) {
                            if (cancelled) {
                                cancelAll();
                                return;
                            }

                            if (em == ErrorMode.IMMEDIATE) {
                                Throwable ex = errors.get();
                                if (ex != null) {
                                    current = null;
                                    inner.cancel();
                                    cancelAll();

                                    a.onError(errors.terminate());
                                    return;
                                }
                            }

                            boolean d = inner.isDone();

                            R v;

                            try {
                                v = q.poll();
                            } catch (Throwable ex) {
                                Exceptions.throwIfFatal(ex);
                                current = null;
                                inner.cancel();
                                cancelAll();
                                a.onError(ex);
                                return;
                            }

                            boolean empty = v == null;

                            if (d && empty) {
                                inner = null;
                                current = null;
                                upstream.request(1);
                                continueNextSource = true;
                                break;
                            }

                            if (empty) {
                                break;
                            }

                            a.onNext(v);

                            e++;

                            inner.requestOne();
                        }

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

                            if (em == ErrorMode.IMMEDIATE) {
                                Throwable ex = errors.get();
                                if (ex != null) {
                                    current = null;
                                    inner.cancel();
                                    cancelAll();

                                    a.onError(errors.terminate());
                                    return;
                                }
                            }

                            boolean d = inner.isDone();

                            boolean empty = q.isEmpty();

                            if (d && empty) {
                                inner = null;
                                current = null;
                                upstream.request(1);
                                continueNextSource = true;
                            }
                        }
                    }
                }

                if (e != 0L && r != Long.MAX_VALUE) {
                    requested.addAndGet(-e);
                }

                if (continueNextSource) {
                    continue;
                }

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