84 lines
3.1 KiB
Java
84 lines
3.1 KiB
Java
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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*
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* Written by Doug Lea with assistance from members of JCP JSR-166
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* Expert Group and released to the public domain, as explained at
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* http://creativecommons.org/publicdomain/zero/1.0/
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*/
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import java.util.concurrent.TimeUnit;
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import java.util.concurrent.locks.AbstractQueuedSynchronizer;
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import java.util.concurrent.locks.Condition;
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import java.util.concurrent.locks.Lock;
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import java.io.IOException;
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import java.io.ObjectInputStream;
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/**
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* A sample user extension of AbstractQueuedSynchronizer.
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*/
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public class Mutex implements Lock, java.io.Serializable {
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private static class Sync extends AbstractQueuedSynchronizer {
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public boolean isHeldExclusively() { return getState() == 1; }
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public boolean tryAcquire(int acquires) {
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assert acquires == 1; // Does not use multiple acquires
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return compareAndSetState(0, 1);
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}
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public boolean tryRelease(int releases) {
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setState(0);
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return true;
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}
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Condition newCondition() { return new ConditionObject(); }
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private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
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s.defaultReadObject();
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setState(0); // reset to unlocked state
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}
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}
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private final Sync sync = new Sync();
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public void lock() {
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sync.acquire(1);
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}
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public boolean tryLock() {
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return sync.tryAcquire(1);
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}
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public void lockInterruptibly() throws InterruptedException {
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sync.acquireInterruptibly(1);
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}
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public boolean tryLock(long timeout, TimeUnit unit) throws InterruptedException {
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return sync.tryAcquireNanos(1, unit.toNanos(timeout));
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}
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public void unlock() { sync.release(1); }
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public Condition newCondition() { return sync.newCondition(); }
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public boolean isLocked() { return sync.isHeldExclusively(); }
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public boolean hasQueuedThreads() { return sync.hasQueuedThreads(); }
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}
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