/**
* Copyright (c) 2002-2013 "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.kernel.impl.nioneo.store;
import java.nio.channels.FileChannel;
import java.util.LinkedList;
import org.neo4j.kernel.impl.transaction.LockException;
/**
* Makes a {@link PersistenceWindow} "lockable" meaning it can be locked by a
* thread during a operation making sure no other thread use the same window
* concurrently.
*/
abstract class LockableWindow implements PersistenceWindow
{
public abstract Buffer getBuffer();
public abstract long position();
public abstract int size();
public abstract void force();
public abstract void close();
private OperationType type = null;
private final FileChannel fileChannel;
private Thread lockingThread = null;
private final LinkedList<LockElement> waitingThreadList =
new LinkedList<LockElement>();
private int lockCount = 0;
private int marked = 0;
LockableWindow( FileChannel fileChannel )
{
this.fileChannel = fileChannel;
}
boolean encapsulates( long position )
{
return position() <= position && position < position() + size();
}
FileChannel getFileChannel()
{
return fileChannel;
}
OperationType getOperationType()
{
return type;
}
void setOperationType( OperationType type )
{
this.type = type;
}
synchronized void mark()
{
this.marked++;
}
synchronized boolean isMarked()
{
return marked > 0;
}
private static class LockElement
{
private final Thread thread;
private boolean movedOn = false;
LockElement( Thread thread )
{
this.thread = thread;
}
}
synchronized void lock()
{
Thread currentThread = Thread.currentThread();
LockElement le = new LockElement( currentThread );
while ( lockCount > 0 && lockingThread != currentThread )
{
waitingThreadList.addFirst( le );
try
{
wait();
}
catch ( InterruptedException e )
{
Thread.interrupted();
}
}
lockCount++;
lockingThread = currentThread;
le.movedOn = true;
marked--;
}
synchronized void unLock()
{
Thread currentThread = Thread.currentThread();
if ( lockCount == 0 )
{
throw new LockException( "" + currentThread
+ " don't have window lock on " + this );
}
lockCount--;
if ( lockCount == 0 )
{
lockingThread = null;
if ( waitingThreadList.size() > 0 )
{
LockElement le = waitingThreadList.removeLast();
if ( !le.movedOn )
{
le.thread.interrupt();
}
}
}
}
synchronized int getWaitingThreadsCount()
{
return waitingThreadList.size();
}
}