org.opendaylight.bgpcep.programming.NanotimeUtil Maven / Gradle / Ivy
/*
* Copyright (c) 2013 Cisco Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.bgpcep.programming;
import java.util.concurrent.TimeUnit;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.programming.rev150720.Nanotime;
import org.opendaylight.yangtools.yang.common.Uint64;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Util methods for {@link Nanotime}.
*/
public final class NanotimeUtil {
private static final Logger LOG = LoggerFactory.getLogger(NanotimeUtil.class);
private static volatile Long nanoTimeOffset = null;
private NanotimeUtil() {
// Hidden on purpose
}
/**
* Returns current time in nanoseconds.
*
* @return Nanotime object filled with current time in nanoseconds.
*/
public static Nanotime currentTime() {
final long millis = Uint64.valueOf(System.currentTimeMillis()).longValue();
return new Nanotime(Uint64.fromLongBits(TimeUnit.MILLISECONDS.toNanos(millis)));
}
/**
* Returns calibrated current JVM nano time.
*
* @return Nanotime object filled with current JVM nano time.
*/
public static Nanotime currentNanoTime() {
if (nanoTimeOffset == null) {
calibrate();
}
return new Nanotime(Uint64.fromLongBits(System.nanoTime() + nanoTimeOffset.longValue()));
}
/**
* Calibrates the offset between the real-time clock providing System.currentTimeMillis() and the monotonic clock
* providing System.nanoTime(). This method should be called whenever there is a hint of the two diverging: either
* when time shifts or periodically.
*/
private static void calibrate() {
final long tm1 = System.currentTimeMillis();
final long nt1 = System.nanoTime();
final long tm2 = System.currentTimeMillis();
final long nt2 = System.nanoTime();
LOG.debug("Calibrated currentTime and nanoTime to {}m <= {}n <= {}m <= {}n", tm1, nt1, tm2, nt2);
final long tm = (tm1 + tm2) / 2;
final long nt = (nt1 + nt2) / 2;
nanoTimeOffset = Long.valueOf(TimeUnit.MILLISECONDS.toNanos(tm) - nt);
}
}