/*
 * Copyright (c) 2011-2017 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
 *
 *       https://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.concurrent.Callable;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

import reactor.core.CoreSubscriber;
import reactor.core.Disposable;
import reactor.core.Fuseable;
import reactor.core.Scannable;
import reactor.core.scheduler.Scheduler;
import reactor.util.annotation.Nullable;

Executes a Callable and emits its value on the given Scheduler.
Type parameters:
  • <T> – the value type
See Also:
/** * Executes a Callable and emits its value on the given Scheduler. * * @param <T> the value type * @see <a href="https://github.com/reactor/reactive-streams-commons">https://github.com/reactor/reactive-streams-commons</a> */
final class FluxSubscribeOnCallable<T> extends Flux<T> implements Fuseable, Scannable { final Callable<? extends T> callable; final Scheduler scheduler; FluxSubscribeOnCallable(Callable<? extends T> callable, Scheduler scheduler) { this.callable = Objects.requireNonNull(callable, "callable"); this.scheduler = Objects.requireNonNull(scheduler, "scheduler"); } @Override public void subscribe(CoreSubscriber<? super T> actual) { CallableSubscribeOnSubscription<T> parent = new CallableSubscribeOnSubscription<>(actual, callable, scheduler); actual.onSubscribe(parent); try { Disposable f = scheduler.schedule(parent); parent.setMainFuture(f); } catch (RejectedExecutionException ree) { if(parent.state != CallableSubscribeOnSubscription.HAS_CANCELLED) { actual.onError(Operators.onRejectedExecution(ree, actual.currentContext())); } } } @Override public Object scanUnsafe(Attr key) { if (key == Attr.RUN_ON) return scheduler; if (key == Attr.RUN_STYLE) return Attr.RunStyle.ASYNC; return null; } static final class CallableSubscribeOnSubscription<T> implements QueueSubscription<T>, InnerProducer<T>, Runnable { final CoreSubscriber<? super T> actual; final Callable<? extends T> callable; final Scheduler scheduler; volatile int state; @SuppressWarnings("rawtypes") static final AtomicIntegerFieldUpdater<CallableSubscribeOnSubscription> STATE = AtomicIntegerFieldUpdater.newUpdater(CallableSubscribeOnSubscription.class, "state"); T value; static final int NO_REQUEST_HAS_VALUE = 1; static final int HAS_REQUEST_NO_VALUE = 2; static final int HAS_REQUEST_HAS_VALUE = 3; static final int HAS_CANCELLED = 4; int fusionState; static final int NO_VALUE = 1; static final int HAS_VALUE = 2; static final int COMPLETE = 3; volatile Disposable mainFuture; @SuppressWarnings("rawtypes") static final AtomicReferenceFieldUpdater<CallableSubscribeOnSubscription, Disposable> MAIN_FUTURE = AtomicReferenceFieldUpdater.newUpdater( CallableSubscribeOnSubscription.class, Disposable.class, "mainFuture"); volatile Disposable requestFuture; @SuppressWarnings("rawtypes") static final AtomicReferenceFieldUpdater<CallableSubscribeOnSubscription, Disposable> REQUEST_FUTURE = AtomicReferenceFieldUpdater.newUpdater( CallableSubscribeOnSubscription.class, Disposable.class, "requestFuture"); CallableSubscribeOnSubscription(CoreSubscriber<? super T> actual, Callable<? extends T> callable, Scheduler scheduler) { this.actual = actual; this.callable = callable; this.scheduler = scheduler; } @Override public CoreSubscriber<? super T> actual() { return actual; } @Override @Nullable public Object scanUnsafe(Attr key) { if (key == Attr.CANCELLED) return state == HAS_CANCELLED; if (key == Attr.BUFFERED) return value != null ? 1 : 0; if (key == Attr.RUN_ON) return scheduler; if (key == Attr.RUN_STYLE) return Attr.RunStyle.ASYNC; return InnerProducer.super.scanUnsafe(key); } @Override public void cancel() { state = HAS_CANCELLED; fusionState = COMPLETE; Disposable a = mainFuture; if (a != OperatorDisposables.DISPOSED) { a = MAIN_FUTURE.getAndSet(this, OperatorDisposables.DISPOSED); if (a != null && a != OperatorDisposables.DISPOSED) { a.dispose(); } } a = requestFuture; if (a != OperatorDisposables.DISPOSED) { a = REQUEST_FUTURE.getAndSet(this, OperatorDisposables.DISPOSED); if (a != null && a != OperatorDisposables.DISPOSED) { a.dispose(); } } } @Override public void clear() { value = null; fusionState = COMPLETE; } @Override public boolean isEmpty() { return fusionState == COMPLETE; } @Override @Nullable public T poll() { if (fusionState == HAS_VALUE) { fusionState = COMPLETE; return value; } return null; } @Override public int requestFusion(int requestedMode) { if ((requestedMode & ASYNC) != 0 && (requestedMode & THREAD_BARRIER) == 0) { fusionState = NO_VALUE; return ASYNC; } return NONE; } @Override public int size() { return isEmpty() ? 0 : 1; } void setMainFuture(Disposable c) { for (; ; ) { Disposable a = mainFuture; if (a == OperatorDisposables.DISPOSED) { c.dispose(); return; } if (MAIN_FUTURE.compareAndSet(this, a, c)) { return; } } } void setRequestFuture(Disposable c) { for (; ; ) { Disposable a = requestFuture; if (a == OperatorDisposables.DISPOSED) { c.dispose(); return; } if (REQUEST_FUTURE.compareAndSet(this, a, c)) { return; } } } @Override public void run() { T v; try { v = callable.call(); } catch (Throwable ex) { actual.onError(Operators.onOperatorError(this, ex, actual.currentContext())); return; } if (v == null) { fusionState = COMPLETE; actual.onComplete(); return; } for (; ; ) { int s = state; if (s == HAS_CANCELLED || s == HAS_REQUEST_HAS_VALUE || s == NO_REQUEST_HAS_VALUE) { return; } if (s == HAS_REQUEST_NO_VALUE) { if (fusionState == NO_VALUE) { this.value = v; this.fusionState = HAS_VALUE; } actual.onNext(v); if (state != HAS_CANCELLED) { actual.onComplete(); } return; } this.value = v; if (STATE.compareAndSet(this, s, NO_REQUEST_HAS_VALUE)) { return; } } } @Override public void request(long n) { if (Operators.validate(n)) { for (; ; ) { int s = state; if (s == HAS_CANCELLED || s == HAS_REQUEST_NO_VALUE || s == HAS_REQUEST_HAS_VALUE) { return; } if (s == NO_REQUEST_HAS_VALUE) { if (STATE.compareAndSet(this, s, HAS_REQUEST_HAS_VALUE)) { try { Disposable f = scheduler.schedule(this::emitValue); setRequestFuture(f); } catch (RejectedExecutionException ree) { actual.onError(Operators.onRejectedExecution(ree, actual.currentContext())); } } return; } if (STATE.compareAndSet(this, s, HAS_REQUEST_NO_VALUE)) { return; } } } } void emitValue() { if (fusionState == NO_VALUE) { this.fusionState = HAS_VALUE; } T v = value; clear(); if (v != null) { actual.onNext(v); } if (state != HAS_CANCELLED) { actual.onComplete(); } } } }