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Diffstat (limited to 'java/JACE/Concurrency/Semaphore.java')
| -rw-r--r-- | java/JACE/Concurrency/Semaphore.java | 263 |
1 files changed, 0 insertions, 263 deletions
diff --git a/java/JACE/Concurrency/Semaphore.java b/java/JACE/Concurrency/Semaphore.java deleted file mode 100644 index 5e558035aee..00000000000 --- a/java/JACE/Concurrency/Semaphore.java +++ /dev/null @@ -1,263 +0,0 @@ -/************************************************* - * - * = PACKAGE - * JACE.Concurrency - * - * = FILENAME - * Semaphore.java - * - *@author Prashant Jain - * - *************************************************/ -package JACE.Concurrency; - -import java.util.*; -import JACE.ASX.*; - -/** - * Implementation of Dijkstra's counting semaphore in java. - * <P> - * <EM>This class does not support recursive semantics.</EM> - */ -public class Semaphore extends LockAdapter -{ - static class TimedWaitSAdapter extends JACE.ASX.TimedWait - { - TimedWaitSAdapter (Object obj) - { - super (obj); - } - - // Check to see if there are any semaphores available. - public boolean condition () - { - return this.count_ > 0; - } - - // Increment the count by one - public void increment () - { - this.count_++; - } - - // Decrement the count by one - public void decrement () - { - this.count_--; - } - - // Set the count - public void count (int c) - { - this.count_ = c; - } - - public int count () - { - return this.count_; - } - - private int count_ = 0; - } - - /** - * Create a Semaphore. - *@param count semaphore count - */ - public Semaphore (int c) - { - this.monitor_.count (c); - this.owners_ = new Hashtable (c); - } - - /** - * Create a binary Semaphore. - */ - public Semaphore () - { - this.monitor_.count (1); - this.owners_ = new Hashtable (1); - } - - public synchronized int tryAcquire () - { - if (this.monitor_.condition ()) { - this.monitor_.decrement (); - setOwner (); - return AbstractLock.SUCCESS; - } else - return AbstractLock.FAILURE; - } - - /** - * Acquire the Semaphore. Throws a TimeoutException if the semaphore - * isn't acquired before the given absolute time. - *@param tv time (TimeValue) to wait until before throwing a - * TimeoutException (unless the semaphore is acquired before that) - *@exception TimeoutException wait timed out exception - *@exception InterruptedException exception during wait - */ - public synchronized int acquire (TimeValue tv) - throws TimeoutException, InterruptedException - { - if (this.monitor_.condition ()) { - this.monitor_.decrement (); - setOwner (); - return AbstractLock.SUCCESS; - } - - numberOfWaiters_++; - - try { - sleepHook (); - this.monitor_.timedWait (tv); - } finally { - numberOfWaiters_--; - } - - this.monitor_.decrement (); - setOwner (); - - return AbstractLock.SLEEPHOOK; - } - - public synchronized int release () - { - if (!isOwner ()) - return AbstractLock.FAILURE; - - if (!signalNextRenewer ()) { - this.monitor_.increment (); - this.monitor_.signal (); - clearOwner (); - } - - return AbstractLock.SUCCESS; - } - - /** - * Checks any objects in the renewers queue, giving one of them - * the lock if it is appropriate. Assumes the synchronization - * lock is already held. - * - *@return true if a renewer was signaled, else false - */ - protected boolean signalNextRenewer () - { - // First find the renewer with the minimum yieldTo count, processing - // all of them along the way. - if (this.renewers_.size() > 0) { - - RenewObject renewer = (RenewObject)renewers_. - elementAt (renewers_.size () - 1); - - renewer.decrementYieldTo (); - - for (int i = this.renewers_.size() - 2; i >=0; i--) { - - RenewObject rwo = (RenewObject)renewers_.elementAt (i); - - rwo.decrementYieldTo (); - - renewer = renewer.min (rwo); - } - - // If the renewer with the minimum yieldTo count has yielded to - // enough threads, or if there are no waiting threads, it should - // be signaled (thus, it wakes up and obtains the lock again). - - if (renewer.condition () || numberOfWaiters_ == 0) { - // Note that we leave monitor_.inUse in the true state so - // we are assured that only the renewer (and not another - // Thread that does an acquire) will gain control. This - // is important since the renew method can't be synchronized - // in its current implementation. - renewers_.removeElement(renewer); - - synchronized (renewer) { - renewer.signal (); - } - - return true; - } - } - - return false; - } - - public int renew (int requeuePosition, - JACE.ASX.TimeValue timeout) - throws InterruptedException, - TimeoutException - { - RenewObject rwo; - - synchronized (this) { - - if (!this.isOwner ()) - return AbstractLock.FAILURE; - - if (numberOfWaiters_ == 0 || - requeuePosition == 0 || - this.monitor_.condition ()) - return AbstractLock.SUCCESS; - - if (requeuePosition < 0 || requeuePosition > numberOfWaiters_) - requeuePosition = numberOfWaiters_; - - rwo = new RenewObject (requeuePosition); - - this.release (); - this.renewers_.addElement (rwo); - } - - boolean exceptionOccured = true; - try { - synchronized (rwo) { - rwo.timedWait (timeout); - - exceptionOccured = false; - } - } finally { - synchronized (this) { - - if (exceptionOccured) { - if (!renewers_.removeElement (rwo)) { - setOwner (); - release (); - } - } else { - setOwner(); - } - } - } - - // By this point, we should know that we have the lock. The inUse - // flag is never set to false in the release() call from the Thread - // that gave us control. That thread also set the owner value. - - return AbstractLock.SUCCESS; - } - - protected boolean isOwner () - { - return owners_.containsKey (accessorID()); - } - - protected void setOwner () - { - owners_.put (accessorID(), this); - } - - protected void clearOwner () - { - owners_.remove (accessorID()); - } - - private TimedWaitSAdapter monitor_ = new TimedWaitSAdapter (this); - // The monitor (adapter) to wait on - - private Hashtable owners_; - private Vector renewers_ = new Vector (); - private int numberOfWaiters_ = 0; -} |