/*
 * 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.scheduler;

import reactor.core.Disposable;
import reactor.core.Disposables;
import reactor.core.Exceptions;
import reactor.core.Scannable;

Executes tasks on the caller's thread immediately.

Use the ImmediateScheduler.instance() to get a shared, stateless instance of this scheduler. This scheduler is NOT time-capable (can't schedule with delay / periodically).

Author:Stephane Maldini
/** * Executes tasks on the caller's thread immediately. * <p> * Use the ImmediateScheduler.instance() to get a shared, stateless instance of this scheduler. * This scheduler is NOT time-capable (can't schedule with delay / periodically). * * @author Stephane Maldini */
final class ImmediateScheduler implements Scheduler, Scannable { private static final ImmediateScheduler INSTANCE; static { INSTANCE = new ImmediateScheduler(); INSTANCE.start(); } public static Scheduler instance() { return INSTANCE; } private ImmediateScheduler() { } static final Disposable FINISHED = Disposables.disposed(); @Override public Disposable schedule(Runnable task) { task.run(); return FINISHED; } @Override public void dispose() { //NO-OP } @Override public Object scanUnsafe(Attr key) { if (key == Attr.TERMINATED || key == Attr.CANCELLED) return isDisposed(); if (key == Attr.NAME) return Schedulers.IMMEDIATE; return null; } @Override public Worker createWorker() { return new ImmediateSchedulerWorker(); } static final class ImmediateSchedulerWorker implements Scheduler.Worker, Scannable { volatile boolean shutdown; @Override public Disposable schedule(Runnable task) { if (shutdown) { throw Exceptions.failWithRejected(); } task.run(); return FINISHED; } @Override public void dispose() { shutdown = true; } @Override public boolean isDisposed() { return shutdown; } @Override public Object scanUnsafe(Attr key) { if (key == Attr.TERMINATED || key == Attr.CANCELLED) return shutdown; if (key == Attr.NAME) return Schedulers.IMMEDIATE + ".worker"; return null; } } }