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/*
* Copyright 2013-2014 Richard M. Hightower
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* __________ _____ __ .__
* \______ \ ____ ____ ____ /\ / \ _____ | | _|__| ____ ____
* | | _// _ \ / _ \ / \ \/ / \ / \\__ \ | |/ / |/ \ / ___\
* | | ( <_> | <_> ) | \ /\ / Y \/ __ \| <| | | \/ /_/ >
* |______ /\____/ \____/|___| / \/ \____|__ (____ /__|_ \__|___| /\___ /
* \/ \/ \/ \/ \/ \//_____/
* ____. ___________ _____ ______________.___.
* | |____ ___ _______ \_ _____/ / _ \ / _____/\__ | |
* | \__ \\ \/ /\__ \ | __)_ / /_\ \ \_____ \ / | |
* /\__| |/ __ \\ / / __ \_ | \/ | \/ \ \____ |
* \________(____ /\_/ (____ / /_______ /\____|__ /_______ / / ______|
* \/ \/ \/ \/ \/ \/
*/
package org.boon.core.timer;
import org.boon.core.Sys;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.ReentrantLock;
/* This timer is used for caches and such
* It is a default timer.
* It should never be used direct.
* There should always be a fall back.
* By default this will reset the time every 100 times it is called to the latest
* System.nanoTime
* At most 1 thread will incur the cost of calling nanoTime about every 100 invocations.
*
*/
public class TimeKeeperBasic implements TimeKeeper {
private final AtomicInteger callEveryNowAndThen = new AtomicInteger();
private final AtomicLong time = new AtomicLong();
private final int TIME_KEEPER_FREQUENCY = Sys.sysProp( "org.boon.timekeeper.frequency", 100 );
private final ReentrantLock lock = new ReentrantLock();
private final AtomicLong lastDeltaTime = new AtomicLong();
@Override
public final long time() {
long limit = callEveryNowAndThen.incrementAndGet();
long time;
boolean shouldGetTime = false;
if ( limit > TIME_KEEPER_FREQUENCY ) {
callEveryNowAndThen.set( 0 );
shouldGetTime = true;
}
/* Somewhat Ensure two calls to time do not return the exact same value. */
time = this.time.get() + limit;
if ( !shouldGetTime && ( limit % 20 == 0 ) ) {
checkForDrift( time );
}
return time;
}
/* Never let the drift get greater than 200 ms. */
private long checkForDrift( long time ) {
long delta = Math.abs( System.currentTimeMillis() - time );
long lastDelta = lastDeltaTime.getAndSet( delta );
if ( delta > lastDelta + 200 ) {
return getTheTime( time );
}
return time;
}
private long getTheTime( long time ) {
boolean locked = lock.tryLock(); //make sure two or more threads are not calling nanoTime.
if ( locked ) {
try {
//I don't want more than one thread calling nanoTime
time = System.nanoTime() / 1_000_000;
this.time.set( time );
return time;
} finally {
lock.unlock();
}
}
return time;
}
}