/*
 * Copyright (c) 2011-2018 Pivotal Software Inc, All Rights Reserved.
 *
 * 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 reactor.core.publisher;

import java.util.Objects;
import java.util.Queue;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.function.Function;
import java.util.function.Supplier;

import org.reactivestreams.Publisher;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Exceptions;
import reactor.core.Fuseable;
import reactor.util.annotation.Nullable;
import reactor.util.context.Context;

import static reactor.core.Exceptions.TERMINATED;

Maps each upstream value into a Publisher and concatenates them into one sequence of items.
Type parameters:
  • <T> – the source value type
  • <R> – the output value type
See Also:
/** * Maps each upstream value into a Publisher and concatenates them into one * sequence of items. * * @param <T> the source value type * @param <R> the output value type * * @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a> */
final class FluxConcatMap<T, R> extends FluxOperator<T, R> { final Function<? super T, ? extends Publisher<? extends R>> mapper; final Supplier<? extends Queue<T>> queueSupplier; final int prefetch; final ErrorMode errorMode;
Indicates when an error from the main source should be reported.
/** * Indicates when an error from the main source should be reported. */
enum ErrorMode {
Report the error immediately, cancelling the active inner source.
/** * Report the error immediately, cancelling the active inner source. */
IMMEDIATE,
Report error after an inner source terminated.
/** * Report error after an inner source terminated. */
BOUNDARY,
Report the error after all sources terminated.
/** * Report the error after all sources terminated. */
END } static <T, R> CoreSubscriber<T> subscriber(CoreSubscriber<? super R> s, Function<? super T, ? extends Publisher<? extends R>> mapper, Supplier<? extends Queue<T>> queueSupplier, int prefetch, ErrorMode errorMode) { switch (errorMode) { case BOUNDARY: return new ConcatMapDelayed<>(s, mapper, queueSupplier, prefetch, false); case END: return new ConcatMapDelayed<>(s, mapper, queueSupplier, prefetch, true); default: return new ConcatMapImmediate<>(s, mapper, queueSupplier, prefetch); } } FluxConcatMap(Flux<? extends T> source, Function<? super T, ? extends Publisher<? extends R>> mapper, Supplier<? extends Queue<T>> queueSupplier, int prefetch, ErrorMode errorMode) { super(source); if (prefetch <= 0) { throw new IllegalArgumentException("prefetch > 0 required but it was " + prefetch); } this.mapper = Objects.requireNonNull(mapper, "mapper"); this.queueSupplier = Objects.requireNonNull(queueSupplier, "queueSupplier"); this.prefetch = prefetch; this.errorMode = Objects.requireNonNull(errorMode, "errorMode"); } @Override public int getPrefetch() { return prefetch; } @Override public void subscribe(CoreSubscriber<? super R> actual) { if (FluxFlatMap.trySubscribeScalarMap(source, actual, mapper, false)) { return; } source.subscribe(subscriber(actual, mapper, queueSupplier, prefetch, errorMode)); } static final class ConcatMapImmediate<T, R> implements FluxConcatMapSupport<T, R> { final CoreSubscriber<? super R> actual; final Context ctx; final ConcatMapInner<R> inner; final Function<? super T, ? extends Publisher<? extends R>> mapper; final Supplier<? extends Queue<T>> queueSupplier; final int prefetch; final int limit; Subscription s; int consumed; volatile Queue<T> queue; volatile boolean done; volatile boolean cancelled; volatile Throwable error; @SuppressWarnings("rawtypes") static final AtomicReferenceFieldUpdater<ConcatMapImmediate, Throwable> ERROR = AtomicReferenceFieldUpdater.newUpdater(ConcatMapImmediate.class, Throwable.class, "error"); volatile boolean active; volatile int wip; @SuppressWarnings("rawtypes") static final AtomicIntegerFieldUpdater<ConcatMapImmediate> WIP = AtomicIntegerFieldUpdater.newUpdater(ConcatMapImmediate.class, "wip"); volatile int guard; @SuppressWarnings("rawtypes") static final AtomicIntegerFieldUpdater<ConcatMapImmediate> GUARD = AtomicIntegerFieldUpdater.newUpdater(ConcatMapImmediate.class, "guard"); int sourceMode; ConcatMapImmediate(CoreSubscriber<? super R> actual, Function<? super T, ? extends Publisher<? extends R>> mapper, Supplier<? extends Queue<T>> queueSupplier, int prefetch) { this.actual = actual; this.ctx = actual.currentContext(); this.mapper = mapper; this.queueSupplier = queueSupplier; this.prefetch = prefetch; this.limit = Operators.unboundedOrLimit(prefetch); this.inner = new ConcatMapInner<>(this); } @Override @Nullable public Object scanUnsafe(Attr key) { if (key == Attr.PARENT) return s; if (key == Attr.TERMINATED) return done || error == TERMINATED; if (key == Attr.CANCELLED) return cancelled; if (key == Attr.PREFETCH) return prefetch; if (key == Attr.BUFFERED) return queue != null ? queue.size() : 0; if (key == Attr.ERROR) return error; return FluxConcatMapSupport.super.scanUnsafe(key); } @Override public void onSubscribe(Subscription s) { if (Operators.validate(this.s, s)) { this.s = s; if (s instanceof Fuseable.QueueSubscription) { @SuppressWarnings("unchecked") Fuseable.QueueSubscription<T> f = (Fuseable.QueueSubscription<T>) s; int m = f.requestFusion(Fuseable.ANY | Fuseable.THREAD_BARRIER); if (m == Fuseable.SYNC) { sourceMode = Fuseable.SYNC; queue = f; done = true; actual.onSubscribe(this); drain(); return; } else if (m == Fuseable.ASYNC) { sourceMode = Fuseable.ASYNC; queue = f; } else { queue = queueSupplier.get(); } } else { queue = queueSupplier.get(); } actual.onSubscribe(this); s.request(Operators.unboundedOrPrefetch(prefetch)); } } @Override public void onNext(T t) { if (sourceMode == Fuseable.ASYNC) { drain(); } else if (!queue.offer(t)) { onError(Operators.onOperatorError(s, Exceptions.failWithOverflow(Exceptions.BACKPRESSURE_ERROR_QUEUE_FULL), t, this.ctx)); Operators.onDiscard(t, this.ctx); } else { drain(); } } @Override public void onError(Throwable t) { if (Exceptions.addThrowable(ERROR, this, t)) { inner.cancel(); if (GUARD.getAndIncrement(this) == 0) { t = Exceptions.terminate(ERROR, this); if (t != TERMINATED) { actual.onError(t); Operators.onDiscardQueueWithClear(queue, this.ctx, null); } } } else { Operators.onErrorDropped(t, this.ctx); } } @Override public void onComplete() { done = true; drain(); } @Override public void innerNext(R value) { if (guard == 0 && GUARD.compareAndSet(this, 0, 1)) { actual.onNext(value); if (GUARD.compareAndSet(this, 1, 0)) { return; } Throwable e = Exceptions.terminate(ERROR, this); if (e != TERMINATED) { actual.onError(e); } } } @Override public void innerComplete() { active = false; drain(); } @Override public void innerError(Throwable e) { e = Operators.onNextInnerError(e, currentContext(), s); if(e != null) { if (Exceptions.addThrowable(ERROR, this, e)) { s.cancel(); if (GUARD.getAndIncrement(this) == 0) { e = Exceptions.terminate(ERROR, this); if (e != TERMINATED) { actual.onError(e); } } } else { Operators.onErrorDropped(e, this.ctx); } } else { active = false; drain(); } } @Override public CoreSubscriber<? super R> actual() { return actual; } @Override public void request(long n) { inner.request(n); } @Override public void cancel() { if (!cancelled) { cancelled = true; inner.cancel(); s.cancel(); Operators.onDiscardQueueWithClear(queue, this.ctx, null); } } void drain() { if (WIP.getAndIncrement(this) == 0) { for (; ; ) { if (cancelled) { return; } if (!active) { boolean d = done; T v; try { v = queue.poll(); } catch (Throwable e) { actual.onError(Operators.onOperatorError(s, e, this.ctx)); return; } boolean empty = v == null; if (d && empty) { actual.onComplete(); return; } if (!empty) { Publisher<? extends R> p; try { p = Objects.requireNonNull(mapper.apply(v), "The mapper returned a null Publisher"); } catch (Throwable e) { Operators.onDiscard(v, this.ctx); Throwable e_ = Operators.onNextError(v, e, this.ctx, s); if (e_ != null) { actual.onError(Operators.onOperatorError(s, e, v, this.ctx)); return; } else { continue; } } if (sourceMode != Fuseable.SYNC) { int c = consumed + 1; if (c == limit) { consumed = 0; s.request(c); } else { consumed = c; } } if (p instanceof Callable) { @SuppressWarnings("unchecked") Callable<R> callable = (Callable<R>) p; R vr; try { vr = callable.call(); } catch (Throwable e) { Throwable e_ = Operators.onNextError(v, e, this.ctx, s); if (e_ != null) { actual.onError(Operators.onOperatorError(s, e, v, this.ctx)); return; } else { continue; } } if (vr == null) { continue; } if (inner.isUnbounded()) { if (guard == 0 && GUARD.compareAndSet(this, 0, 1)) { actual.onNext(vr); if (!GUARD.compareAndSet(this, 1, 0)) { Throwable e = Exceptions.terminate(ERROR, this); if (e != TERMINATED) { actual.onError(e); } return; } } continue; } else { active = true; inner.set(new WeakScalarSubscription<>(vr, inner)); } } else { active = true; p.subscribe(inner); } } } if (WIP.decrementAndGet(this) == 0) { break; } } } } } static final class WeakScalarSubscription<T> implements Subscription { final CoreSubscriber<? super T> actual; final T value; boolean once; WeakScalarSubscription(T value, CoreSubscriber<? super T> actual) { this.value = value; this.actual = actual; } @Override public void request(long n) { if (n > 0 && !once) { once = true; Subscriber<? super T> a = actual; a.onNext(value); a.onComplete(); } } @Override public void cancel() { Operators.onDiscard(value, actual.currentContext()); } } static final class ConcatMapDelayed<T, R> implements FluxConcatMapSupport<T, R> { final CoreSubscriber<? super R> actual; final Context ctx; final ConcatMapInner<R> inner; final Function<? super T, ? extends Publisher<? extends R>> mapper; final Supplier<? extends Queue<T>> queueSupplier; final int prefetch; final int limit; final boolean veryEnd; Subscription s; int consumed; volatile Queue<T> queue; volatile boolean done; volatile boolean cancelled; volatile Throwable error; @SuppressWarnings("rawtypes") static final AtomicReferenceFieldUpdater<ConcatMapDelayed, Throwable> ERROR = AtomicReferenceFieldUpdater.newUpdater(ConcatMapDelayed.class, Throwable.class, "error"); volatile boolean active; volatile int wip; @SuppressWarnings("rawtypes") static final AtomicIntegerFieldUpdater<ConcatMapDelayed> WIP = AtomicIntegerFieldUpdater.newUpdater(ConcatMapDelayed.class, "wip"); int sourceMode; ConcatMapDelayed(CoreSubscriber<? super R> actual, Function<? super T, ? extends Publisher<? extends R>> mapper, Supplier<? extends Queue<T>> queueSupplier, int prefetch, boolean veryEnd) { this.actual = actual; this.ctx = actual.currentContext(); this.mapper = mapper; this.queueSupplier = queueSupplier; this.prefetch = prefetch; this.limit = Operators.unboundedOrLimit(prefetch); this.veryEnd = veryEnd; this.inner = new ConcatMapInner<>(this); } @Override public CoreSubscriber<? super R> actual() { return actual; } @Override @Nullable public Object scanUnsafe(Attr key) { if (key == Attr.PARENT) return s; if (key == Attr.TERMINATED) return done; if (key == Attr.CANCELLED) return cancelled; if (key == Attr.PREFETCH) return prefetch; if (key == Attr.BUFFERED) return queue != null ? queue.size() : 0; if (key == Attr.ERROR) return error; if (key == Attr.DELAY_ERROR) return true; return FluxConcatMapSupport.super.scanUnsafe(key); } @Override public void onSubscribe(Subscription s) { if (Operators.validate(this.s, s)) { this.s = s; if (s instanceof Fuseable.QueueSubscription) { @SuppressWarnings("unchecked") Fuseable.QueueSubscription<T> f = (Fuseable.QueueSubscription<T>) s; int m = f.requestFusion(Fuseable.ANY | Fuseable.THREAD_BARRIER); if (m == Fuseable.SYNC) { sourceMode = Fuseable.SYNC; queue = f; done = true; actual.onSubscribe(this); drain(); return; } else if (m == Fuseable.ASYNC) { sourceMode = Fuseable.ASYNC; queue = f; } else { queue = queueSupplier.get(); } } else { queue = queueSupplier.get(); } actual.onSubscribe(this); s.request(Operators.unboundedOrPrefetch(prefetch)); } } @Override public void onNext(T t) { if (sourceMode == Fuseable.ASYNC) { drain(); } else if (!queue.offer(t)) { onError(Operators.onOperatorError(s, Exceptions.failWithOverflow(Exceptions.BACKPRESSURE_ERROR_QUEUE_FULL), t, this.ctx)); Operators.onDiscard(t, this.ctx); } else { drain(); } } @Override public void onError(Throwable t) { if (Exceptions.addThrowable(ERROR, this, t)) { done = true; drain(); } else { Operators.onErrorDropped(t, this.ctx); } } @Override public void onComplete() { done = true; drain(); } @Override public void innerNext(R value) { actual.onNext(value); } @Override public void innerComplete() { active = false; drain(); } @Override public void innerError(Throwable e) { e = Operators.onNextInnerError(e, currentContext(), s); if(e != null) { if (Exceptions.addThrowable(ERROR, this, e)) { if (!veryEnd) { s.cancel(); done = true; } active = false; drain(); } else { Operators.onErrorDropped(e, this.ctx); } } else { active = false; } } @Override public void request(long n) { inner.request(n); } @Override public void cancel() { if (!cancelled) { cancelled = true; inner.cancel(); s.cancel(); Operators.onDiscardQueueWithClear(queue, this.ctx, null); } } void drain() { if (WIP.getAndIncrement(this) == 0) { for (; ; ) { if (cancelled) { return; } if (!active) { boolean d = done; if (d && !veryEnd) { Throwable ex = error; if (ex != null) { ex = Exceptions.terminate(ERROR, this); if (ex != TERMINATED) { actual.onError(ex); } return; } } T v; try { v = queue.poll(); } catch (Throwable e) { actual.onError(Operators.onOperatorError(s, e, this.ctx)); return; } boolean empty = v == null; if (d && empty) { Throwable ex = Exceptions.terminate(ERROR, this); if (ex != null && ex != TERMINATED) { actual.onError(ex); } else { actual.onComplete(); } return; } if (!empty) { Publisher<? extends R> p; try { p = Objects.requireNonNull(mapper.apply(v), "The mapper returned a null Publisher"); } catch (Throwable e) { Operators.onDiscard(v, this.ctx); Throwable e_ = Operators.onNextError(v, e, this.ctx, s); if (e_ != null) { actual.onError(Operators.onOperatorError(s, e, v, this.ctx)); return; } else { continue; } } if (sourceMode != Fuseable.SYNC) { int c = consumed + 1; if (c == limit) { consumed = 0; s.request(c); } else { consumed = c; } } if (p instanceof Callable) { @SuppressWarnings("unchecked") Callable<R> supplier = (Callable<R>) p; R vr; try { vr = supplier.call(); } catch (Throwable e) { //does the strategy apply? if so, short-circuit the delayError. In any case, don't cancel Throwable e_ = Operators.onNextPollError(v, e, this.ctx); if (e_ == null) { continue; } //now if error mode strategy doesn't apply, let delayError play if (veryEnd && Exceptions.addThrowable(ERROR, this, e)) { continue; } else { actual.onError(Operators.onOperatorError(s, e, v, this.ctx)); return; } } if (vr == null) { continue; } if (inner.isUnbounded()) { actual.onNext(vr); continue; } else { active = true; inner.set(new WeakScalarSubscription<>(vr, inner)); } } else { active = true; p.subscribe(inner); } } } if (WIP.decrementAndGet(this) == 0) { break; } } } } }
Type parameters:
  • <I> – input type consumed by the InnerOperator
  • <T> – output type, as forwarded by the inner this helper supports
/** * @param <I> input type consumed by the InnerOperator * @param <T> output type, as forwarded by the inner this helper supports */
interface FluxConcatMapSupport<I, T> extends InnerOperator<I, T> { void innerNext(T value); void innerComplete(); void innerError(Throwable e); } static final class ConcatMapInner<R> extends Operators.MultiSubscriptionSubscriber<R, R> { final FluxConcatMapSupport<?, R> parent; long produced; ConcatMapInner(FluxConcatMapSupport<?, R> parent) { super(Operators.emptySubscriber()); this.parent = parent; } @Override public Context currentContext() { return parent.currentContext(); } @Nullable @Override public Object scanUnsafe(Attr key) { if (key == Attr.ACTUAL) return parent; return super.scanUnsafe(key); } @Override public void onNext(R t) { produced++; parent.innerNext(t); } @Override public void onError(Throwable t) { long p = produced; if (p != 0L) { produced = 0L; produced(p); } parent.innerError(t); } @Override public void onComplete() { long p = produced; if (p != 0L) { produced = 0L; produced(p); } parent.innerComplete(); } } }