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/*
* Copyright 2005-2008 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;
/**
* Utility class to provide a more accurate replacement for
* System.currentTimeMillis().
*/
class J3dClock {
// Issue 543 - Flag to indicate whether clock skews are taken in account
// and corrected. false by default. Set by the "j3d.adjustClockSkew" property.
private static boolean skewAdjustedClock = false;
private static long deltaTime;
private static final long nsecPerMsec = 1000000;
/**
* Private constructor, since no instance should ever be created.
*/
private J3dClock() {
}
/**
* Returns the current time in milliseconds. This is a more
* accurate version of System.currentTimeMillis and should be used in
* its place.
*
* @return the current time in milliseconds.
*/
static long currentTimeMillis() {
if (!skewAdjustedClock) {
return (System.nanoTime() / nsecPerMsec) + deltaTime;
} else {
// Issue 543 - Adjust for possible clock skew
long time = (System.nanoTime() / nsecPerMsec) + deltaTime;
long sysTime = System.currentTimeMillis();
if (Math.abs(time - sysTime) > 50) {
long baseTime, baseTimerValue;
synchronized (J3dClock.class) {
baseTime = System.currentTimeMillis();
baseTimerValue = System.nanoTime();
}
deltaTime = baseTime - (baseTimerValue / nsecPerMsec);
time = (System.nanoTime() / nsecPerMsec) + deltaTime;
}
return time;
}
}
static {
// Issue 543: get property for clock skew adjustment
skewAdjustedClock = MasterControl.getBooleanProperty("j3d.adjustClockSkew",
skewAdjustedClock, "clock skew adjustment");
// Call time methods once without using their values to ensure that
// the methods are "warmed up". We need to make sure that the actual
// calls that we use take place as close together as possible in time.
System.currentTimeMillis();
System.nanoTime();
// Compute deltaTime between System.currentTimeMillis()
// and the high-res timer, use a synchronized block to force both calls
// to be made before the integer divide
long baseTime, baseTimerValue;
synchronized (J3dClock.class) {
baseTime = System.currentTimeMillis();
baseTimerValue = System.nanoTime();
}
deltaTime = baseTime - (baseTimerValue / nsecPerMsec);
}
}
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