com.diozero.api.sandpit.EventQueue Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of diozero-core Show documentation
The newest version!
package com.diozero.api.sandpit;

/*-
 * #%L
 * Organisation: diozero
 * Project:      diozero - Core
 * Filename:     EventQueue.java
 * 
 * This file is part of the diozero project. More information about this project
 * can be found at https://www.diozero.com/.
 * %%
 * Copyright (C) 2016 - 2024 diozero
 * %%
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 * #L%
 */

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.function.Consumer;

import com.diozero.api.Event;
import com.diozero.util.DiozeroScheduler;

/**
 * Decouple event producers from consumers so that event production isn't
 * affected by event consumption
 *
 * @param  the class containing the data fields for individual events
 */
public class EventQueue implements Consumer, Runnable, AutoCloseable {
	private final BlockingQueue queue;
	private final List> listeners;
	private final AtomicBoolean running;
	private Future future;

	public EventQueue() {
		queue = new LinkedBlockingQueue<>();
		listeners = new ArrayList<>();
		running = new AtomicBoolean();

		start();
	}

	public void addListener(Consumer listener) {
		listeners.add(listener);
	}

	public void removeListener(Consumer listener) {
		listeners.remove(listener);
	}

	/**
	 * Adds an element to the tail of the queue
	 */
	@Override
	public void accept(T t) {
		queue.offer(t);
	}

	public void start() {
		running.set(true);
		future = DiozeroScheduler.getNonDaemonInstance().submit(this);
	}

	@Override
	public void run() {
		while (running.get()) {
			try {
				T event = queue.take();
				listeners.forEach(listener -> listener.accept(event));
			} catch (InterruptedException e) {
				running.set(false);
				// Set interrupted flag
				Thread.currentThread().interrupt();
			}
			/*-
			// Drain the remaining elements on the queue and process them.
			final Collection remaining_events = new ArrayList<>();
			queue.drainTo(remaining_events);
			remaining_events.forEach(event -> listeners.forEach(listener -> listener.accept(event)));
			*/
		}
	}

	public void stop() {
		running.set(false);
		if (future != null) {
			future.cancel(true);
		}
	}

	@Override
	public void close() {
		stop();
	}
}