/*
* ToroDB
* Copyright © 2014 8Kdata Technology (www.8kdata.com)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package com.torodb.common.util;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.Multimap;
import java.util.EnumSet;
/**
* This class is used to sequencialize several threads.
*
* It is mainly used on concurrency scenarios when a test want to force an specific sequence of
* events.
*
* Any sequencer is associated with an enum class, whose elements are called <em>messages</em>.
* Threads can wait until a message is sent calling the method {@link #waitFor(java.lang.Enum) } or
* can send messages with {@link #notify(java.lang.Enum) }.
*/
public class Sequencer<E extends Enum<E>> {
private final EnumSet<E> sentMessages;
private final Multimap<E, Thread> reservedMessages;
public Sequencer(Class<E> messageClass) {
sentMessages = EnumSet.noneOf(messageClass);
reservedMessages = HashMultimap.create();
}
public void waitFor(E message) {
synchronized (message) {
reservedMessages.put(message, Thread.currentThread());
while (!sentMessages.contains(message)) {
try {
message.wait();
} catch (InterruptedException ex) {
Thread.currentThread().interrupt();
}
}
}
}
public void notify(E message) {
synchronized (message) {
sentMessages.add(message);
message.notifyAll();
}
}
@SuppressWarnings("unchecked")
public void notify(E... message) {
for (E e : message) {
notify(e);
}
}
}