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/*
* Copyright 1999-2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*
*/
package javax.media.j3d;
/**
* Use this lock to allow multiple reads/single write synchronization.
* To prevent deadlock a read/writeLock call must match with a read/writeUnlock call.
* Write request has precedence over read request.
*/
class MRSWLock {
static boolean debug = false;
private int readCount;
private boolean write;
private int writeRequested;
private int lockRequested;
MRSWLock() {
readCount = 0;
write = false;
writeRequested = 0;
lockRequested = 0;
}
synchronized final void readLock() {
lockRequested++;
while((write == true) || (writeRequested > 0)) {
try { wait(); } catch(InterruptedException e){}
}
lockRequested--;
readCount++;
}
synchronized final void readUnlock() {
if(readCount>0)
readCount--;
else
if(debug) System.err.println("ReadWriteLock.java : Problem! readCount is >= 0.");
if(lockRequested>0)
notifyAll();
}
synchronized final void writeLock() {
lockRequested++;
writeRequested++;
while((readCount>0)||(write == true)) {
try { wait(); } catch(InterruptedException e){}
}
write = true;
lockRequested--;
writeRequested--;
}
synchronized final void writeUnlock() {
write = false;
if(lockRequested>0)
notifyAll();
}
}
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