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Barrier.java
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Barrier.java
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/*
* Copyright (c) 2002-2017 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.test;
import java.util.concurrent.CountDownLatch;
/**
* Controls two threads that would otherwise race and produce non-deterministic outcome.
* (ascii-art looks odd in source but lines up in fixed-size generated javadoc).
* <pre>
* {@link Control#await() T1 await()} {@link Control#release() T1 release()}
* | |
* -T1/T2--------|-T2-----------|-T1------------|-T1/T2------------------>
* |
* {@link #reached() T2 reached()}
* </pre>
*/
public interface Barrier
{
Barrier NONE = () ->
{
};
void reached();
class Control implements Barrier
{
private final CountDownLatch reached = new CountDownLatch( 1 );
private final CountDownLatch released = new CountDownLatch( 1 );
@Override
public void reached()
{
try
{
reached.countDown();
released.await();
}
catch ( InterruptedException e )
{
throw new RuntimeException( e );
}
}
public void await() throws InterruptedException
{
reached.await();
}
public void awaitUninterruptibly()
{
boolean interrupted = false;
try
{
while ( true )
{
try
{
await();
return;
}
catch ( InterruptedException e )
{
interrupted = true;
}
}
}
finally
{
if ( interrupted )
{
Thread.currentThread().interrupt();
}
}
}
public void release()
{
released.countDown();
}
}
}