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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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|
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import java.io.ObjectInputStream; |
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import java.io.IOException; |
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import java.util.concurrent.*; |
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import java.util.concurrent.locks.*; |
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|
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class Mutex implements Lock, java.io.Serializable { |
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|
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// Our internal helper class |
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private static class Sync extends AbstractQueuedSynchronizer { |
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// Report whether in locked state |
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protected boolean isHeldExclusively() { |
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return getState() == 1; |
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} |
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|
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// Acquire the lock if state is zero |
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public boolean tryAcquire(int acquires) { |
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assert acquires == 1; // Otherwise unused |
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return compareAndSetState(0, 1); |
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} |
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|
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// Release the lock by setting state to zero |
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protected boolean tryRelease(int releases) { |
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assert releases == 1; // Otherwise unused |
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if (getState() == 0) throw new IllegalMonitorStateException(); |
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setState(0); |
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return true; |
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} |
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|
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// Provide a Condition |
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Condition newCondition() { return new ConditionObject(); } |
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|
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// Deserialize properly |
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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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|
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// The sync object does all the hard work. We just forward to it. |
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private final Sync sync = new Sync(); |
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|
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public void lock() { sync.acquire(1); } |
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public boolean tryLock() { return sync.tryAcquire(1); } |
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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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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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} |
