/*
* Licensed to the Apache Software Foundation (ASF) under one or more contributor license
* agreements. See the NOTICE file distributed with this work for additional information regarding
* copyright ownership. The ASF licenses this file to You 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.
*/
package org.apache.geode.internal.util.concurrent;
import org.apache.geode.CancelCriterion;
import org.apache.geode.internal.Assert;
import org.apache.geode.internal.i18n.LocalizedStrings;
/**
* Extends the CountDownLatch with the ability to also countUp.
* <p>
* Based on the original Doug Lea backport implementation of CountDownLatch.
*
* @see java.util.concurrent.CountDownLatch
*/
public class StoppableCountDownOrUpLatch {
private int count_;
/**
* The cancellation criterion
*/
private CancelCriterion stopper;
/**
* Constructs a <code>CountDownLatch</code> initialized with the given count.
*
* @param count the number of times {@link #countDown} must be invoked before threads can pass
* through {@link #await()}
* @throws IllegalArgumentException if <code>count</count> is negative
*/
public StoppableCountDownOrUpLatch(CancelCriterion stopper, int count) {
Assert.assertTrue(stopper != null);
if (count < 0)
throw new IllegalArgumentException(
LocalizedStrings.StoppableCountDownOrUpLatch_COUNT_0.toLocalizedString());
this.stopper = stopper;
this.count_ = count;
}
/**
* Causes the current thread to wait until the latch has counted down to zero, unless the thread
* is {@linkplain Thread#interrupt interrupted}.
*
* <p>
* If the current count is zero then this method returns immediately.
*
* <p>
* If the current count is greater than zero then the current thread becomes disabled for thread
* scheduling purposes and lies dormant until one of two things happen:
* <ul>
* <li>The count reaches zero due to invocations of the {@link #countDown} method; or
* <li>Some other thread {@linkplain Thread#interrupt interrupts} the current thread.
* </ul>
*
* <p>
* If the current thread:
* <ul>
* <li>has its interrupted status set on entry to this method; or
* <li>is {@linkplain Thread#interrupt interrupted} while waiting,
* </ul>
* then {@link InterruptedException} is thrown and the current thread's interrupted status is
* cleared.
*
* @throws InterruptedException if the current thread is interrupted while waiting
*/
public void await() throws InterruptedException {
if (Thread.interrupted())
throw new InterruptedException();
// Modified to use inner primitive repeatedly, checking
// for cancellation
for (;;) {
stopper.checkCancelInProgress(null);
if (await(StoppableCountDownLatch.RETRY_TIME))
break;
}
}
private static final long NANOS_PER_MS = 1000000;
/**
* Causes the current thread to wait until the latch has counted down to zero, unless the thread
* is {@linkplain Thread#interrupt interrupted}, or the specified waiting time elapses.
*
* <p>
* If the current count is zero then this method returns immediately with the value
* <code>true</code>.
*
* <p>
* If the current count is greater than zero then the current thread becomes disabled for thread
* scheduling purposes and lies dormant until one of three things happen:
* <ul>
* <li>The count reaches zero due to invocations of the {@link #countDown} method; or
* <li>Some other thread {@linkplain Thread#interrupt interrupts} the current thread; or
* <li>The specified waiting time elapses.
* </ul>
*
* <p>
* If the count reaches zero then the method returns with the value <code>true</code>.
*
* <p>
* If the current thread:
* <ul>
* <li>has its interrupted status set on entry to this method; or
* <li>is {@linkplain Thread#interrupt interrupted} while waiting,
* </ul>
* then {@link InterruptedException} is thrown and the current thread's interrupted status is
* cleared.
*
* <p>
* If the specified waiting time elapses then the value <code>false</code> is returned. If the
* time is less than or equal to zero, the method will not wait at all.
*
* @param msTimeout the maximum time to wait in milliseconds
* @return <code>true</code> if the count reached zero and <code>false</code> if the waiting time
* elapsed before the count reached zero
* @throws InterruptedException if the current thread is interrupted while waiting
*/
public boolean await(long msTimeout) throws InterruptedException {
if (Thread.interrupted())
throw new InterruptedException();
long nanos = msTimeout * NANOS_PER_MS; // millis to nanos
synchronized (this) {
if (count_ <= 0)
return true;
else if (nanos <= 0)
return false;
else {
long deadline = System.nanoTime() + nanos;
for (;;) {
stopper.checkCancelInProgress(null);
wait(nanos / NANOS_PER_MS, (int) (nanos % NANOS_PER_MS));
if (count_ <= 0)
return true;
else {
nanos = deadline - System.nanoTime();
if (nanos <= 0)
return false;
}
}
}
}
}
/**
* Decrements the count of the latch, releasing all waiting threads if the count reaches zero.
*
* <p>
* If the current count is greater than zero then it is decremented. If the new count is zero then
* all waiting threads are re-enabled for thread scheduling purposes.
*
* <p>
* If the current count equals zero then nothing happens.
*/
public synchronized void countDown() {
if (count_ == 0)
return;
if (--count_ == 0)
notifyAll();
}
/**
* Returns the current count.
*
* <p>
* This method is typically used for debugging and testing purposes.
*
* @return the current count
*/
public long getCount() {
return count_;
}
/**
* Returns a string identifying this latch, as well as its state. The state, in brackets, includes
* the String <code>"Count ="</code> followed by the current count.
*
* @return a string identifying this latch, as well as its state
*/
@Override
public String toString() {
return super.toString() + "[Count = " + getCount() + "]";
}
/**
* [GemStone addition]
*/
public synchronized void countUp() {
this.count_++;
}
/**
* [GemStone addition]
*/
public synchronized long getCountSync() {
return getCount();
}
}