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

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.disposables.*;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.functions.ObjectHelper;
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 FlowableBufferBoundary<T, U extends Collection<? super T>, Open, Close>
extends AbstractFlowableWithUpstream<T, U> {
    final Callable<U> bufferSupplier;
    final Publisher<? extends Open> bufferOpen;
    final Function<? super Open, ? extends Publisher<? extends Close>> bufferClose;

    public FlowableBufferBoundary(Flowable<T> source, Publisher<? extends Open> bufferOpen,
            Function<? super Open, ? extends Publisher<? extends Close>> bufferClose, Callable<U> bufferSupplier) {
        super(source);
        this.bufferOpen = bufferOpen;
        this.bufferClose = bufferClose;
        this.bufferSupplier = bufferSupplier;
    }

    @Override
    protected void subscribeActual(Subscriber<? super U> s) {
        BufferBoundarySubscriber<T, U, Open, Close> parent =
            new BufferBoundarySubscriber<T, U, Open, Close>(
                s, bufferOpen, bufferClose, bufferSupplier
            );
        s.onSubscribe(parent);
        source.subscribe(parent);
    }

    static final class BufferBoundarySubscriber<T, C extends Collection<? super T>, Open, Close>
    extends AtomicInteger implements FlowableSubscriber<T>, Subscription {

        private static final long serialVersionUID = -8466418554264089604L;

        final Subscriber<? super C> downstream;

        final Callable<C> bufferSupplier;

        final Publisher<? extends Open> bufferOpen;

        final Function<? super Open, ? extends Publisher<? extends Close>> bufferClose;

        final CompositeDisposable subscribers;

        final AtomicLong requested;

        final AtomicReference<Subscription> upstream;

        final AtomicThrowable errors;

        volatile boolean done;

        final SpscLinkedArrayQueue<C> queue;

        volatile boolean cancelled;

        long index;

        Map<Long, C> buffers;

        long emitted;

        BufferBoundarySubscriber(Subscriber<? super C> actual,
                Publisher<? extends Open> bufferOpen,
                Function<? super Open, ? extends Publisher<? extends Close>> bufferClose,
                Callable<C> bufferSupplier
        ) {
            this.downstream = actual;
            this.bufferSupplier = bufferSupplier;
            this.bufferOpen = bufferOpen;
            this.bufferClose = bufferClose;
            this.queue = new SpscLinkedArrayQueue<C>(bufferSize());
            this.subscribers = new CompositeDisposable();
            this.requested = new AtomicLong();
            this.upstream = new AtomicReference<Subscription>();
            this.buffers = new LinkedHashMap<Long, C>();
            this.errors = new AtomicThrowable();
        }

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

                BufferOpenSubscriber<Open> open = new BufferOpenSubscriber<Open>(this);
                subscribers.add(open);

                bufferOpen.subscribe(open);

                s.request(Long.MAX_VALUE);
            }
        }

        @Override
        public void onNext(T t) {
            synchronized (this) {
                Map<Long, C> bufs = buffers;
                if (bufs == null) {
                    return;
                }
                for (C b : bufs.values()) {
                    b.add(t);
                }
            }
        }

        @Override
        public void onError(Throwable t) {
            if (errors.addThrowable(t)) {
                subscribers.dispose();
                synchronized (this) {
                    buffers = null;
                }
                done = true;
                drain();
            } else {
                RxJavaPlugins.onError(t);
            }
        }

        @Override
        public void onComplete() {
            subscribers.dispose();
            synchronized (this) {
                Map<Long, C> bufs = buffers;
                if (bufs == null) {
                    return;
                }
                for (C b : bufs.values()) {
                    queue.offer(b);
                }
                buffers = null;
            }
            done = true;
            drain();
        }

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

        @Override
        public void cancel() {
            if (SubscriptionHelper.cancel(upstream)) {
                cancelled = true;
                subscribers.dispose();
                synchronized (this) {
                    buffers = null;
                }
                if (getAndIncrement() != 0) {
                    queue.clear();
                }
            }
        }

        void open(Open token) {
            Publisher<? extends Close> p;
            C buf;
            try {
                buf = ObjectHelper.requireNonNull(bufferSupplier.call(), "The bufferSupplier returned a null Collection");
                p = ObjectHelper.requireNonNull(bufferClose.apply(token), "The bufferClose returned a null Publisher");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                SubscriptionHelper.cancel(upstream);
                onError(ex);
                return;
            }

            long idx = index;
            index = idx + 1;
            synchronized (this) {
                Map<Long, C> bufs = buffers;
                if (bufs == null) {
                    return;
                }
                bufs.put(idx, buf);
            }

            BufferCloseSubscriber<T, C> bc = new BufferCloseSubscriber<T, C>(this, idx);
            subscribers.add(bc);
            p.subscribe(bc);
        }

        void openComplete(BufferOpenSubscriber<Open> os) {
            subscribers.delete(os);
            if (subscribers.size() == 0) {
                SubscriptionHelper.cancel(upstream);
                done = true;
                drain();
            }
        }

        void close(BufferCloseSubscriber<T, C> closer, long idx) {
            subscribers.delete(closer);
            boolean makeDone = false;
            if (subscribers.size() == 0) {
                makeDone = true;
                SubscriptionHelper.cancel(upstream);
            }
            synchronized (this) {
                Map<Long, C> bufs = buffers;
                if (bufs == null) {
                    return;
                }
                queue.offer(buffers.remove(idx));
            }
            if (makeDone) {
                done = true;
            }
            drain();
        }

        void boundaryError(Disposable subscriber, Throwable ex) {
            SubscriptionHelper.cancel(upstream);
            subscribers.delete(subscriber);
            onError(ex);
        }

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

            int missed = 1;
            long e = emitted;
            Subscriber<? super C> a = downstream;
            SpscLinkedArrayQueue<C> q = queue;

            for (;;) {
                long r = requested.get();

                while (e != r) {
                    if (cancelled) {
                        q.clear();
                        return;
                    }

                    boolean d = done;
                    if (d && errors.get() != null) {
                        q.clear();
                        Throwable ex = errors.terminate();
                        a.onError(ex);
                        return;
                    }

                    C v = q.poll();
                    boolean empty = v == null;

                    if (d && empty) {
                        a.onComplete();
                        return;
                    }

                    if (empty) {
                        break;
                    }

                    a.onNext(v);
                    e++;
                }

                if (e == r) {
                    if (cancelled) {
                        q.clear();
                        return;
                    }

                    if (done) {
                        if (errors.get() != null) {
                            q.clear();
                            Throwable ex = errors.terminate();
                            a.onError(ex);
                            return;
                        } else if (q.isEmpty()) {
                            a.onComplete();
                            return;
                        }
                    }
                }

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

        static final class BufferOpenSubscriber<Open>
        extends AtomicReference<Subscription>
        implements FlowableSubscriber<Open>, Disposable {

            private static final long serialVersionUID = -8498650778633225126L;

            final BufferBoundarySubscriber<?, ?, Open, ?> parent;

            BufferOpenSubscriber(BufferBoundarySubscriber<?, ?, Open, ?> parent) {
                this.parent = parent;
            }

            @Override
            public void onSubscribe(Subscription s) {
                SubscriptionHelper.setOnce(this, s, Long.MAX_VALUE);
            }

            @Override
            public void onNext(Open t) {
                parent.open(t);
            }

            @Override
            public void onError(Throwable t) {
                lazySet(SubscriptionHelper.CANCELLED);
                parent.boundaryError(this, t);
            }

            @Override
            public void onComplete() {
                lazySet(SubscriptionHelper.CANCELLED);
                parent.openComplete(this);
            }

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

            @Override
            public boolean isDisposed() {
                return get() == SubscriptionHelper.CANCELLED;
            }
        }
    }

    static final class BufferCloseSubscriber<T, C extends Collection<? super T>>
    extends AtomicReference<Subscription>
    implements FlowableSubscriber<Object>, Disposable {

        private static final long serialVersionUID = -8498650778633225126L;

        final BufferBoundarySubscriber<T, C, ?, ?> parent;

        final long index;

        BufferCloseSubscriber(BufferBoundarySubscriber<T, C, ?, ?> parent, long index) {
            this.parent = parent;
            this.index = index;
        }

        @Override
        public void onSubscribe(Subscription s) {
            SubscriptionHelper.setOnce(this, s, Long.MAX_VALUE);
        }

        @Override
        public void onNext(Object t) {
            Subscription s = get();
            if (s != SubscriptionHelper.CANCELLED) {
                lazySet(SubscriptionHelper.CANCELLED);
                s.cancel();
                parent.close(this, index);
            }
        }

        @Override
        public void onError(Throwable t) {
            if (get() != SubscriptionHelper.CANCELLED) {
                lazySet(SubscriptionHelper.CANCELLED);
                parent.boundaryError(this, t);
            } else {
                RxJavaPlugins.onError(t);
            }
        }

        @Override
        public void onComplete() {
            if (get() != SubscriptionHelper.CANCELLED) {
                lazySet(SubscriptionHelper.CANCELLED);
                parent.close(this, index);
            }
        }

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

        @Override
        public boolean isDisposed() {
            return get() == SubscriptionHelper.CANCELLED;
        }
    }
}