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/*
* Copyright 2015 Open Networking Laboratory
*
* 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.
*/
package org.onlab.util;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
/**
* Mutable boolean that allows threads to wait for a specified value.
*/
public class BlockingBoolean extends AbstractQueuedSynchronizer {
private static final int TRUE = 1;
private static final int FALSE = 0;
/**
* Creates a new blocking boolean with the specified value.
*
* @param value the starting value
*/
public BlockingBoolean(boolean value) {
setState(value ? TRUE : FALSE);
}
/**
* Causes the current thread to wait until the boolean equals the specified
* value unless the thread is {@linkplain Thread#interrupt interrupted}.
*
* @param value specified value
* @throws InterruptedException if interrupted while waiting
*/
public void await(boolean value) throws InterruptedException {
acquireSharedInterruptibly(value ? TRUE : FALSE);
}
/**
* Causes the current thread to wait until the boolean equals the specified
* value unless the thread is {@linkplain Thread#interrupt interrupted},
* or the specified waiting time elapses.
*
* @param value specified value
* @param timeout the maximum time to wait
* @param unit the time unit of the {@code timeout} argument
* @return {@code true} if the count reached zero and {@code false}
* if the waiting time elapsed before the count reached zero
* @throws InterruptedException if interrupted while waiting
*/
public boolean await(boolean value, long timeout, TimeUnit unit)
throws InterruptedException {
return tryAcquireSharedNanos(value ? TRUE : FALSE, unit.toNanos(timeout));
}
protected int tryAcquireShared(int acquires) {
return (getState() == acquires) ? 1 : -1;
}
/**
* Sets the value of the blocking boolean.
*
* @param value new value
*/
public void set(boolean value) {
releaseShared(value ? TRUE : FALSE);
}
/**
* Gets the value of the blocking boolean.
*
* @return current value
*/
public boolean get() {
return getState() == TRUE;
}
protected boolean tryReleaseShared(int releases) {
// Signal on state change only
int state = getState();
if (state == releases) {
return false;
}
return compareAndSetState(state, releases);
}
}
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