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/** Notice of modification as required by the LGPL
* This file was modified by Gemstone Systems Inc. on
* $Date$
**/
/*
File: LayeredSync.java
Originally written by Doug Lea and released into the public domain.
This may be used for any purposes whatsoever without acknowledgment.
Thanks for the assistance and support of Sun Microsystems Labs,
and everyone contributing, testing, and using this code.
History:
Date Who What
1Aug1998 dl Create public version
*/
package com.gemstone.org.jgroups.oswego.concurrent;
/**
* A class that can be used to compose Syncs.
* A LayeredSync object manages two other Sync objects,
* outer and inner. The acquire operation
* invokes outer.acquire() followed by inner.acquire(),
* but backing out of outer (via release) upon an exception in inner.
* The other methods work similarly.
*
* LayeredSyncs can be used to compose arbitrary chains
* by arranging that either of the managed Syncs be another
* LayeredSync.
*
*
[ Introduction to this package. ]
**/
public class LayeredSync implements Sync {
protected final Sync outer_;
protected final Sync inner_;
/**
* Create a LayeredSync managing the given outer and inner Sync
* objects
**/
public LayeredSync(Sync outer, Sync inner) {
outer_ = outer;
inner_ = inner;
}
public void acquire() throws InterruptedException {
if (Thread.interrupted()) throw new InterruptedException(); // GemStoneAddition
outer_.acquire();
try {
inner_.acquire();
}
catch (InterruptedException ex) {
outer_.release();
throw ex;
}
}
public boolean attempt(long msecs) throws InterruptedException {
if (Thread.interrupted()) throw new InterruptedException(); // GemStoneAddition - for safety
long start = (msecs <= 0)? 0 : System.currentTimeMillis();
long waitTime = msecs;
if (outer_.attempt(waitTime)) {
try {
if (msecs > 0)
waitTime = msecs - (System.currentTimeMillis() - start);
if (inner_.attempt(waitTime))
return true;
else {
outer_.release();
return false;
}
}
catch (InterruptedException ex) {
outer_.release();
throw ex;
}
}
else
return false;
}
public void release() {
inner_.release();
outer_.release();
}
}