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/*
Calimero 2 - A library for KNX network access
Copyright (c) 2006, 2011 B. Malinowsky
This program 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 2 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, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Linking this library statically or dynamically with other modules is
making a combined work based on this library. Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under terms
of your choice, provided that you also meet, for each linked independent
module, the terms and conditions of the license of that module. An
independent module is a module which is not derived from or based on
this library. If you modify this library, you may extend this exception
to your version of the library, but you are not obligated to do so. If
you do not wish to do so, delete this exception statement from your
version.
*/
package tuwien.auto.calimero.buffer.cache;
import tuwien.auto.calimero.exception.KNXIllegalArgumentException;
/**
* Used to remove expired entries from a cache.
*
* The cache sweeper is running in its own thread, waking up for work every sweep time
* interval set by the user. Then {@link Cache#removeExpired()} is invoked on the
* specified cache.
* Interruption policy: complete any ongoing sweeping, then cleanup and exit.
*
* @author B. Malinowsky
* @see Cache
*/
public final class CacheSweeper extends Thread
{
// interval in seconds
private int sweepInterval;
private final Cache cache;
private final Object lock = new Object();
/**
* Creates a {@link CacheSweeper} for cache with the given
* sweepInterval.
*
*
* @param cache the cache for which {@link Cache#removeExpired()} should be invoked
* @param sweepInterval lapse of time between sweeping in seconds
*/
public CacheSweeper(final Cache cache, final int sweepInterval)
{
super("Cache sweeper");
this.cache = cache;
setSweepInterval(sweepInterval);
// priority below normal
setPriority(3);
setDaemon(true);
}
/**
* Sets a new sweep interval.
*
* If the cache sweeper is in waiting state for next sweep, the new interval is
* immediately applied and checked against elapsed time.
*
* @param interval new time interval between sweeping in seconds
*/
public void setSweepInterval(final int interval)
{
if (interval <= 0)
throw new KNXIllegalArgumentException("sweep interval has to be > 0");
synchronized (lock) {
sweepInterval = interval;
lock.notify();
}
}
/**
* Returns the time interval between {@link Cache#removeExpired()} calls used by this
* cache sweeper.
*
*
* @return the time in seconds
*/
public int getSweepInterval()
{
synchronized (lock) {
return sweepInterval;
}
}
/**
* Stops the sweeper and quits the thread.
*
*/
public void stopSweeper()
{
interrupt();
}
/* (non-Javadoc)
* @see java.lang.Thread#run()
*/
public void run()
{
try {
while (true) {
final long start = System.currentTimeMillis();
synchronized (lock) {
long remaining = sweepInterval * 1000;
while (remaining > 0) {
lock.wait(remaining);
remaining = start + sweepInterval * 1000 - System.currentTimeMillis();
}
}
cache.removeExpired();
}
}
catch (final InterruptedException e) {
// just let thread exit
}
}
}