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From ndbe...@apache.org
Subject svn commit: r421111 [6/11] - in /incubator/harmony/enhanced/classlib/trunk/sandbox: ./ juc-proposal/ juc-proposal/concurrent/ juc-proposal/concurrent/.settings/ juc-proposal/concurrent/META-INF/ juc-proposal/concurrent/src/ juc-proposal/concurrent/src/...
Date Wed, 12 Jul 2006 04:12:08 GMT
Added: incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/Semaphore.java
URL: http://svn.apache.org/viewvc/incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/Semaphore.java?rev=421111&view=auto
==============================================================================
--- incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/Semaphore.java (added)
+++ incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/Semaphore.java Tue Jul 11 21:12:04 2006
@@ -0,0 +1,665 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent;
+import java.util.*;
+import java.util.concurrent.locks.*;
+import java.util.concurrent.atomic.*;
+
+/**
+ * A counting semaphore.  Conceptually, a semaphore maintains a set of
+ * permits.  Each {@link #acquire} blocks if necessary until a permit is
+ * available, and then takes it.  Each {@link #release} adds a permit,
+ * potentially releasing a blocking acquirer.
+ * However, no actual permit objects are used; the <tt>Semaphore</tt> just
+ * keeps a count of the number available and acts accordingly.
+ *
+ * <p>Semaphores are often used to restrict the number of threads than can
+ * access some (physical or logical) resource. For example, here is
+ * a class that uses a semaphore to control access to a pool of items:
+ * <pre>
+ * class Pool {
+ *   private static final MAX_AVAILABLE = 100;
+ *   private final Semaphore available = new Semaphore(MAX_AVAILABLE, true);
+ *
+ *   public Object getItem() throws InterruptedException {
+ *     available.acquire();
+ *     return getNextAvailableItem();
+ *   }
+ *
+ *   public void putItem(Object x) {
+ *     if (markAsUnused(x))
+ *       available.release();
+ *   }
+ *
+ *   // Not a particularly efficient data structure; just for demo
+ *
+ *   protected Object[] items = ... whatever kinds of items being managed
+ *   protected boolean[] used = new boolean[MAX_AVAILABLE];
+ *
+ *   protected synchronized Object getNextAvailableItem() {
+ *     for (int i = 0; i < MAX_AVAILABLE; ++i) {
+ *       if (!used[i]) {
+ *          used[i] = true;
+ *          return items[i];
+ *       }
+ *     }
+ *     return null; // not reached
+ *   }
+ *
+ *   protected synchronized boolean markAsUnused(Object item) {
+ *     for (int i = 0; i < MAX_AVAILABLE; ++i) {
+ *       if (item == items[i]) {
+ *          if (used[i]) {
+ *            used[i] = false;
+ *            return true;
+ *          } else
+ *            return false;
+ *       }
+ *     }
+ *     return false;
+ *   }
+ *
+ * }
+ * </pre>
+ *
+ * <p>Before obtaining an item each thread must acquire a permit from
+ * the semaphore, guaranteeing that an item is available for use. When
+ * the thread has finished with the item it is returned back to the
+ * pool and a permit is returned to the semaphore, allowing another
+ * thread to acquire that item.  Note that no synchronization lock is
+ * held when {@link #acquire} is called as that would prevent an item
+ * from being returned to the pool.  The semaphore encapsulates the
+ * synchronization needed to restrict access to the pool, separately
+ * from any synchronization needed to maintain the consistency of the
+ * pool itself.
+ *
+ * <p>A semaphore initialized to one, and which is used such that it
+ * only has at most one permit available, can serve as a mutual
+ * exclusion lock.  This is more commonly known as a <em>binary
+ * semaphore</em>, because it only has two states: one permit
+ * available, or zero permits available.  When used in this way, the
+ * binary semaphore has the property (unlike many {@link Lock}
+ * implementations), that the &quot;lock&quot; can be released by a
+ * thread other than the owner (as semaphores have no notion of
+ * ownership).  This can be useful in some specialized contexts, such
+ * as deadlock recovery.
+ *
+ * <p> The constructor for this class optionally accepts a
+ * <em>fairness</em> parameter. When set false, this class makes no
+ * guarantees about the order in which threads acquire permits. In
+ * particular, <em>barging</em> is permitted, that is, a thread
+ * invoking {@link #acquire} can be allocated a permit ahead of a
+ * thread that has been waiting.  When fairness is set true, the
+ * semaphore guarantees that threads invoking any of the {@link
+ * #acquire() acquire} methods are allocated permits in the order in
+ * which their invocation of those methods was processed
+ * (first-in-first-out; FIFO). Note that FIFO ordering necessarily
+ * applies to specific internal points of execution within these
+ * methods.  So, it is possible for one thread to invoke
+ * <tt>acquire</tt> before another, but reach the ordering point after
+ * the other, and similarly upon return from the method.
+ *
+ * <p>Generally, semaphores used to control resource access should be
+ * initialized as fair, to ensure that no thread is starved out from
+ * accessing a resource. When using semaphores for other kinds of
+ * synchronization control, the throughput advantages of non-fair
+ * ordering often outweigh fairness considerations.
+ *
+ * <p>This class also provides convenience methods to {@link
+ * #acquire(int) acquire} and {@link #release(int) release} multiple
+ * permits at a time.  Beware of the increased risk of indefinite
+ * postponement when these methods are used without fairness set true.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ *
+ */
+
+public class Semaphore implements java.io.Serializable {
+    private static final long serialVersionUID = -3222578661600680210L;
+    /** All mechanics via AbstractQueuedSynchronizer subclass */
+    private final Sync sync;
+
+    /**
+     * Synchronization implementation for semaphore.  Uses AQS state
+     * to represent permits. Subclassed into fair and nonfair
+     * versions.
+     */
+    abstract static class Sync extends AbstractQueuedSynchronizer {
+        Sync(int permits) {
+            setState(permits);
+        }
+        
+        final int getPermits() {
+            return getState();
+        }
+
+        final int nonfairTryAcquireShared(int acquires) {
+            for (;;) {
+                int available = getState();
+                int remaining = available - acquires;
+                if (remaining < 0 ||
+                    compareAndSetState(available, remaining))
+                    return remaining;
+            }
+        }
+        
+        protected final boolean tryReleaseShared(int releases) {
+            for (;;) {
+                int p = getState();
+                if (compareAndSetState(p, p + releases)) 
+                    return true;
+            }
+        }
+
+        final void reducePermits(int reductions) {
+            for (;;) {
+                int current = getState();
+                int next = current - reductions;
+                if (compareAndSetState(current, next))
+                    return;
+            }
+        }
+
+        final int drainPermits() {
+            for (;;) {
+                int current = getState();
+                if (current == 0 || compareAndSetState(current, 0))
+                    return current;
+            }
+        }
+    }
+
+    /**
+     * NonFair version
+     */
+    final static class NonfairSync extends Sync {
+        NonfairSync(int permits) {
+            super(permits);
+        }
+       
+        protected int tryAcquireShared(int acquires) {
+            return nonfairTryAcquireShared(acquires);
+        }
+    }
+
+    /**
+     * Fair version
+     */
+    final static class FairSync extends Sync {
+        FairSync(int permits) {
+            super(permits);
+        }
+        
+        protected int tryAcquireShared(int acquires) {
+            Thread current = Thread.currentThread();
+            for (;;) {
+                Thread first = getFirstQueuedThread();
+                if (first != null && first != current)
+                    return -1;
+                int available = getState();
+                int remaining = available - acquires;
+                if (remaining < 0 ||
+                    compareAndSetState(available, remaining))
+                    return remaining;
+            }
+        }
+    }
+
+    /**
+     * Creates a <tt>Semaphore</tt> with the given number of
+     * permits and nonfair fairness setting.
+     * @param permits the initial number of permits available. This
+     * value may be negative, in which case releases must
+     * occur before any acquires will be granted.
+     */
+    public Semaphore(int permits) { 
+        sync = new NonfairSync(permits);
+    }
+
+    /**
+     * Creates a <tt>Semaphore</tt> with the given number of
+     * permits and the given fairness setting.
+     * @param permits the initial number of permits available. This
+     * value may be negative, in which case releases must
+     * occur before any acquires will be granted.
+     * @param fair true if this semaphore will guarantee first-in
+     * first-out granting of permits under contention, else false.
+     */
+    public Semaphore(int permits, boolean fair) { 
+        sync = (fair)? new FairSync(permits) : new NonfairSync(permits);
+    }
+
+    /**
+     * Acquires a permit from this semaphore, blocking until one is
+     * available, or the thread is {@link Thread#interrupt interrupted}.
+     *
+     * <p>Acquires a permit, if one is available and returns immediately,
+     * reducing the number of available permits by one.
+     * <p>If no permit is available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until
+     * one of two things happens:
+     * <ul>
+     * <li>Some other thread invokes the {@link #release} method for this
+     * semaphore and the current thread is next to be assigned a permit; or
+     * <li>Some other thread {@link 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 {@link Thread#interrupt interrupted} while waiting
+     * for a permit,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     *
+     * @throws InterruptedException if the current thread is interrupted
+     *
+     * @see Thread#interrupt
+     */
+    public void acquire() throws InterruptedException {
+        sync.acquireSharedInterruptibly(1);
+    }
+
+    /**
+     * Acquires a permit from this semaphore, blocking until one is
+     * available.
+     *
+     * <p>Acquires a permit, if one is available and returns immediately,
+     * reducing the number of available permits by one.
+     * <p>If no permit is available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until
+     * some other thread invokes the {@link #release} method for this
+     * semaphore and the current thread is next to be assigned a permit.
+     *
+     * <p>If the current thread
+     * is {@link Thread#interrupt interrupted} while waiting
+     * for a permit then it will continue to wait, but the time at which
+     * the thread is assigned a permit may change compared to the time it
+     * would have received the permit had no interruption occurred. When the
+     * thread does return from this method its interrupt status will be set.
+     *
+     */
+    public void acquireUninterruptibly() {
+        sync.acquireShared(1);
+    }
+
+    /**
+     * Acquires a permit from this semaphore, only if one is available at the 
+     * time of invocation.
+     * <p>Acquires a permit, if one is available and returns immediately,
+     * with the value <tt>true</tt>,
+     * reducing the number of available permits by one.
+     *
+     * <p>If no permit is available then this method will return
+     * immediately with the value <tt>false</tt>.
+     *
+     * <p>Even when this semaphore has been set to use a
+     * fair ordering policy, a call to <tt>tryAcquire()</tt> <em>will</em>
+     * immediately acquire a permit if one is available, whether or not
+     * other threads are currently waiting. 
+     * This &quot;barging&quot; behavior can be useful in certain 
+     * circumstances, even though it breaks fairness. If you want to honor
+     * the fairness setting, then use 
+     * {@link #tryAcquire(long, TimeUnit) tryAcquire(0, TimeUnit.SECONDS) }
+     * which is almost equivalent (it also detects interruption).
+     *
+     * @return <tt>true</tt> if a permit was acquired and <tt>false</tt>
+     * otherwise.
+     */
+    public boolean tryAcquire() {
+        return sync.nonfairTryAcquireShared(1) >= 0;
+    }
+
+    /**
+     * Acquires a permit from this semaphore, if one becomes available 
+     * within the given waiting time and the
+     * current thread has not been {@link Thread#interrupt interrupted}.
+     * <p>Acquires a permit, if one is available and returns immediately,
+     * with the value <tt>true</tt>,
+     * reducing the number of available permits by one.
+     * <p>If no permit is available then
+     * the current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until one of three things happens:
+     * <ul>
+     * <li>Some other thread invokes the {@link #release} method for this
+     * semaphore and the current thread is next to be assigned a permit; or
+     * <li>Some other thread {@link Thread#interrupt interrupts} the current
+     * thread; or
+     * <li>The specified waiting time elapses.
+     * </ul>
+     * <p>If a permit is acquired then the value <tt>true</tt> is returned.
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@link Thread#interrupt interrupted} while waiting to acquire
+     * a permit,
+     * </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 <tt>false</tt>
+     * is returned.
+     * If the time is less than or equal to zero, the method will not wait 
+     * at all.
+     *
+     * @param timeout the maximum time to wait for a permit
+     * @param unit the time unit of the <tt>timeout</tt> argument.
+     * @return <tt>true</tt> if a permit was acquired and <tt>false</tt>
+     * if the waiting time elapsed before a permit was acquired.
+     *
+     * @throws InterruptedException if the current thread is interrupted
+     *
+     * @see Thread#interrupt
+     *
+     */
+    public boolean tryAcquire(long timeout, TimeUnit unit) 
+        throws InterruptedException {
+        return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));
+    }
+
+    /**
+     * Releases a permit, returning it to the semaphore.
+     * <p>Releases a permit, increasing the number of available permits
+     * by one.
+     * If any threads are blocking trying to acquire a permit, then one
+     * is selected and given the permit that was just released.
+     * That thread is re-enabled for thread scheduling purposes.
+     * <p>There is no requirement that a thread that releases a permit must
+     * have acquired that permit by calling {@link #acquire}.
+     * Correct usage of a semaphore is established by programming convention
+     * in the application.
+     */
+    public void release() {
+        sync.releaseShared(1);
+    }
+       
+    /**
+     * Acquires the given number of permits from this semaphore, 
+     * blocking until all are available, 
+     * or the thread is {@link Thread#interrupt interrupted}.
+     *
+     * <p>Acquires the given number of permits, if they are available,
+     * and returns immediately,
+     * reducing the number of available permits by the given amount.
+     *
+     * <p>If insufficient permits are available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until
+     * one of two things happens:
+     * <ul>
+     * <li>Some other thread invokes one of the {@link #release() release} 
+     * methods for this semaphore, the current thread is next to be assigned
+     * permits and the number of available permits satisfies this request; or
+     * <li>Some other thread {@link 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 {@link Thread#interrupt interrupted} while waiting
+     * for a permit,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared. 
+     * Any permits that were to be assigned to this thread are instead 
+     * assigned to the next waiting thread(s), as if
+     * they had been made available by a call to {@link #release()}.
+     *
+     * @param permits the number of permits to acquire
+     *
+     * @throws InterruptedException if the current thread is interrupted
+     * @throws IllegalArgumentException if permits less than zero.
+     *
+     * @see Thread#interrupt
+     */
+    public void acquire(int permits) throws InterruptedException {
+        if (permits < 0) throw new IllegalArgumentException();
+        sync.acquireSharedInterruptibly(permits);
+    }
+
+    /**
+     * Acquires the given number of permits from this semaphore, 
+     * blocking until all are available.
+     *
+     * <p>Acquires the given number of permits, if they are available,
+     * and returns immediately,
+     * reducing the number of available permits by the given amount.
+     *
+     * <p>If insufficient permits are available then the current thread becomes
+     * disabled for thread scheduling purposes and lies dormant until
+     * some other thread invokes one of the {@link #release() release} 
+     * methods for this semaphore, the current thread is next to be assigned
+     * permits and the number of available permits satisfies this request.
+     *
+     * <p>If the current thread
+     * is {@link Thread#interrupt interrupted} while waiting
+     * for permits then it will continue to wait and its position in the
+     * queue is not affected. When the
+     * thread does return from this method its interrupt status will be set.
+     *
+     * @param permits the number of permits to acquire
+     * @throws IllegalArgumentException if permits less than zero.
+     *
+     */
+    public void acquireUninterruptibly(int permits) {
+        if (permits < 0) throw new IllegalArgumentException();
+        sync.acquireShared(permits);
+    }
+
+    /**
+     * Acquires the given number of permits from this semaphore, only
+     * if all are available at the time of invocation.
+     *
+     * <p>Acquires the given number of permits, if they are available, and 
+     * returns immediately, with the value <tt>true</tt>,
+     * reducing the number of available permits by the given amount.
+     *
+     * <p>If insufficient permits are available then this method will return
+     * immediately with the value <tt>false</tt> and the number of available
+     * permits is unchanged.
+     *
+     * <p>Even when this semaphore has been set to use a fair ordering
+     * policy, a call to <tt>tryAcquire</tt> <em>will</em>
+     * immediately acquire a permit if one is available, whether or
+     * not other threads are currently waiting.  This
+     * &quot;barging&quot; behavior can be useful in certain
+     * circumstances, even though it breaks fairness. If you want to
+     * honor the fairness setting, then use {@link #tryAcquire(int,
+     * long, TimeUnit) tryAcquire(permits, 0, TimeUnit.SECONDS) }
+     * which is almost equivalent (it also detects interruption).
+     *
+     * @param permits the number of permits to acquire
+     *
+     * @return <tt>true</tt> if the permits were acquired and <tt>false</tt>
+     * otherwise.
+     * @throws IllegalArgumentException if permits less than zero.
+     */
+    public boolean tryAcquire(int permits) {
+        if (permits < 0) throw new IllegalArgumentException();
+        return sync.nonfairTryAcquireShared(permits) >= 0;
+    }
+
+    /**
+     * Acquires the given number of permits from this semaphore, if all 
+     * become available within the given waiting time and the
+     * current thread has not been {@link Thread#interrupt interrupted}.
+     * <p>Acquires the given number of permits, if they are available and 
+     * returns immediately, with the value <tt>true</tt>,
+     * reducing the number of available permits by the given amount.
+     * <p>If insufficient permits are available then
+     * the current thread becomes disabled for thread scheduling
+     * purposes and lies dormant until one of three things happens:
+     * <ul>
+     * <li>Some other thread invokes one of the {@link #release() release} 
+     * methods for this semaphore, the current thread is next to be assigned
+     * permits and the number of available permits satisfies this request; or
+     * <li>Some other thread {@link Thread#interrupt interrupts} the current
+     * thread; or
+     * <li>The specified waiting time elapses.
+     * </ul>
+     * <p>If the permits are acquired then the value <tt>true</tt> is returned.
+     * <p>If the current thread:
+     * <ul>
+     * <li>has its interrupted status set on entry to this method; or
+     * <li>is {@link Thread#interrupt interrupted} while waiting to acquire
+     * the permits,
+     * </ul>
+     * then {@link InterruptedException} is thrown and the current thread's
+     * interrupted status is cleared.
+     * Any permits that were to be assigned to this thread, are instead 
+     * assigned to the next waiting thread(s), as if
+     * they had been made available by a call to {@link #release()}.
+     *
+     * <p>If the specified waiting time elapses then the value <tt>false</tt>
+     * is returned.
+     * If the time is
+     * less than or equal to zero, the method will not wait at all.
+     * Any permits that were to be assigned to this thread, are instead 
+     * assigned to the next waiting thread(s), as if
+     * they had been made available by a call to {@link #release()}.
+     *
+     * @param permits the number of permits to acquire
+     * @param timeout the maximum time to wait for the permits
+     * @param unit the time unit of the <tt>timeout</tt> argument.
+     * @return <tt>true</tt> if all permits were acquired and <tt>false</tt>
+     * if the waiting time elapsed before all permits were acquired.
+     *
+     * @throws InterruptedException if the current thread is interrupted
+     * @throws IllegalArgumentException if permits less than zero.
+     *
+     * @see Thread#interrupt
+     *
+     */
+    public boolean tryAcquire(int permits, long timeout, TimeUnit unit)
+        throws InterruptedException {
+        if (permits < 0) throw new IllegalArgumentException();
+        return sync.tryAcquireSharedNanos(permits, unit.toNanos(timeout));
+    }
+
+    /**
+     * Releases the given number of permits, returning them to the semaphore.
+     * <p>Releases the given number of permits, increasing the number of 
+     * available permits by that amount.
+     * If any threads are blocking trying to acquire permits, then the
+     * one that has been waiting the longest
+     * is selected and given the permits that were just released.
+     * If the number of available permits satisfies that thread's request
+     * then that thread is re-enabled for thread scheduling purposes; otherwise
+     * the thread continues to wait. If there are still permits available
+     * after the first thread's request has been satisfied, then those permits
+     * are assigned to the next waiting thread. If it is satisfied then it is
+     * re-enabled for thread scheduling purposes. This continues until there
+     * are insufficient permits to satisfy the next waiting thread, or there
+     * are no more waiting threads.
+     *
+     * <p>There is no requirement that a thread that releases a permit must
+     * have acquired that permit by calling {@link Semaphore#acquire acquire}.
+     * Correct usage of a semaphore is established by programming convention
+     * in the application.
+     *
+     * @param permits the number of permits to release
+     * @throws IllegalArgumentException if permits less than zero.
+     */
+    public void release(int permits) {
+        if (permits < 0) throw new IllegalArgumentException();
+        sync.releaseShared(permits);
+    }
+
+    /**
+     * Returns the current number of permits available in this semaphore.
+     * <p>This method is typically used for debugging and testing purposes.
+     * @return the number of permits available in this semaphore.
+     */
+    public int availablePermits() {
+        return sync.getPermits();
+    }
+
+    /**
+     * Acquire and return all permits that are immediately available.
+     * @return the number of permits 
+     */
+    public int drainPermits() {
+        return sync.drainPermits();
+    }
+
+    /**
+     * Shrinks the number of available permits by the indicated
+     * reduction. This method can be useful in subclasses that use
+     * semaphores to track resources that become unavailable. This
+     * method differs from <tt>acquire</tt> in that it does not block
+     * waiting for permits to become available.
+     * @param reduction the number of permits to remove
+     * @throws IllegalArgumentException if reduction is negative
+     */
+    protected void reducePermits(int reduction) {
+	if (reduction < 0) throw new IllegalArgumentException();
+        sync.reducePermits(reduction);
+    }
+
+    /**
+     * Returns true if this semaphore has fairness set true.
+     * @return true if this semaphore has fairness set true.
+     */
+    public boolean isFair() {
+        return sync instanceof FairSync;
+    }
+
+    /**
+     * Queries whether any threads are waiting to acquire. Note that
+     * because cancellations may occur at any time, a <tt>true</tt>
+     * return does not guarantee that any other thread will ever
+     * acquire.  This method is designed primarily for use in
+     * monitoring of the system state.
+     *
+     * @return true if there may be other threads waiting to acquire
+     * the lock.
+     */
+    public final boolean hasQueuedThreads() { 
+        return sync.hasQueuedThreads();
+    }
+
+    /**
+     * Returns an estimate of the number of threads waiting to
+     * acquire.  The value is only an estimate because the number of
+     * threads may change dynamically while this method traverses
+     * internal data structures.  This method is designed for use in
+     * monitoring of the system state, not for synchronization
+     * control.
+     * @return the estimated number of threads waiting for this lock
+     */
+    public final int getQueueLength() {
+        return sync.getQueueLength();
+    }
+
+    /**
+     * Returns a collection containing threads that may be waiting to
+     * acquire.  Because the actual set of threads may change
+     * dynamically while constructing this result, the returned
+     * collection is only a best-effort estimate.  The elements of the
+     * returned collection are in no particular order.  This method is
+     * designed to facilitate construction of subclasses that provide
+     * more extensive monitoring facilities.
+     * @return the collection of threads
+     */
+    protected Collection<Thread> getQueuedThreads() {
+        return sync.getQueuedThreads();
+    }
+
+    /**
+     * Returns a string identifying this semaphore, as well as its state.
+     * The state, in brackets, includes the String 
+     * &quot;Permits =&quot; followed by the number of permits.
+     * @return a string identifying this semaphore, as well as its
+     * state
+     */
+    public String toString() {
+        return super.toString() + "[Permits = " + sync.getPermits() + "]";
+    }
+
+}

Propchange: incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/Semaphore.java
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    svn:eol-style = native

Added: incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/SynchronousQueue.java
URL: http://svn.apache.org/viewvc/incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/SynchronousQueue.java?rev=421111&view=auto
==============================================================================
--- incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/SynchronousQueue.java (added)
+++ incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/SynchronousQueue.java Tue Jul 11 21:12:04 2006
@@ -0,0 +1,685 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent;
+import java.util.concurrent.locks.*;
+import java.util.*;
+
+/**
+ * A {@linkplain BlockingQueue blocking queue} in which each
+ * <tt>put</tt> must wait for a <tt>take</tt>, and vice versa.  A
+ * synchronous queue does not have any internal capacity, not even a
+ * capacity of one. You cannot <tt>peek</tt> at a synchronous queue
+ * because an element is only present when you try to take it; you
+ * cannot add an element (using any method) unless another thread is
+ * trying to remove it; you cannot iterate as there is nothing to
+ * iterate.  The <em>head</em> of the queue is the element that the
+ * first queued thread is trying to add to the queue; if there are no
+ * queued threads then no element is being added and the head is
+ * <tt>null</tt>.  For purposes of other <tt>Collection</tt> methods
+ * (for example <tt>contains</tt>), a <tt>SynchronousQueue</tt> acts
+ * as an empty collection.  This queue does not permit <tt>null</tt>
+ * elements.
+ *
+ * <p>Synchronous queues are similar to rendezvous channels used in
+ * CSP and Ada. They are well suited for handoff designs, in which an
+ * object running in one thread must sync up with an object running
+ * in another thread in order to hand it some information, event, or
+ * task.
+ *
+ * <p> This class supports an optional fairness policy for ordering
+ * waiting producer and consumer threads.  By default, this ordering
+ * is not guaranteed. However, a queue constructed with fairness set
+ * to <tt>true</tt> grants threads access in FIFO order. Fairness
+ * generally decreases throughput but reduces variability and avoids
+ * starvation.
+ *
+ * <p>This class implements all of the <em>optional</em> methods
+ * of the {@link Collection} and {@link Iterator} interfaces.
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/../guide/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <E> the type of elements held in this collection
+ */
+public class SynchronousQueue<E> extends AbstractQueue<E>
+        implements BlockingQueue<E>, java.io.Serializable {
+    private static final long serialVersionUID = -3223113410248163686L;
+
+    /*
+      This implementation divides actions into two cases for puts:
+
+      * An arriving producer that does not already have a waiting consumer
+      creates a node holding item, and then waits for a consumer to take it.
+      * An arriving producer that does already have a waiting consumer fills
+      the slot node created by the consumer, and notifies it to continue.
+
+      And symmetrically, two for takes:
+
+      * An arriving consumer that does not already have a waiting producer
+      creates an empty slot node, and then waits for a producer to fill it.
+      * An arriving consumer that does already have a waiting producer takes
+      item from the node created by the producer, and notifies it to continue.
+
+      When a put or take waiting for the actions of its counterpart
+      aborts due to interruption or timeout, it marks the node
+      it created as "CANCELLED", which causes its counterpart to retry
+      the entire put or take sequence.
+
+      This requires keeping two simple queues, waitingProducers and
+      waitingConsumers. Each of these can be FIFO (preserves fairness)
+      or LIFO (improves throughput).
+    */
+
+    /** Lock protecting both wait queues */
+    private final ReentrantLock qlock;
+    /** Queue holding waiting puts */
+    private final WaitQueue waitingProducers;
+    /** Queue holding waiting takes */
+    private final WaitQueue waitingConsumers;
+
+    /**
+     * Creates a <tt>SynchronousQueue</tt> with nonfair access policy.
+     */
+    public SynchronousQueue() {
+        this(false);
+    }
+
+    /**
+     * Creates a <tt>SynchronousQueue</tt> with specified fairness policy.
+     * @param fair if true, threads contend in FIFO order for access;
+     * otherwise the order is unspecified.
+     */
+    public SynchronousQueue(boolean fair) {
+        if (fair) {
+            qlock = new ReentrantLock(true);
+            waitingProducers = new FifoWaitQueue();
+            waitingConsumers = new FifoWaitQueue();
+        }
+        else {
+            qlock = new ReentrantLock();
+            waitingProducers = new LifoWaitQueue();
+            waitingConsumers = new LifoWaitQueue();
+        }
+    }
+
+    /**
+     * Queue to hold waiting puts/takes; specialized to Fifo/Lifo below.
+     * These queues have all transient fields, but are serializable
+     * in order to recover fairness settings when deserialized.
+     */
+    static abstract class WaitQueue implements java.io.Serializable {
+        /** Create, add, and return node for x */
+        abstract Node enq(Object x);
+        /** Remove and return node, or null if empty */
+        abstract Node deq();
+    }
+
+    /**
+     * FIFO queue to hold waiting puts/takes.
+     */
+    static final class FifoWaitQueue extends WaitQueue implements java.io.Serializable {
+        private static final long serialVersionUID = -3623113410248163686L;
+        private transient Node head;
+        private transient Node last;
+
+        Node enq(Object x) {
+            Node p = new Node(x);
+            if (last == null)
+                last = head = p;
+            else
+                last = last.next = p;
+            return p;
+        }
+
+        Node deq() {
+            Node p = head;
+            if (p != null) {
+                if ((head = p.next) == null)
+                    last = null;
+                p.next = null;
+            }
+            return p;
+        }
+    }
+
+    /**
+     * LIFO queue to hold waiting puts/takes.
+     */
+    static final class LifoWaitQueue extends WaitQueue implements java.io.Serializable {
+        private static final long serialVersionUID = -3633113410248163686L;
+        private transient Node head;
+
+        Node enq(Object x) {
+            return head = new Node(x, head);
+        }
+
+        Node deq() {
+            Node p = head;
+            if (p != null) {
+                head = p.next;
+                p.next = null;
+            }
+            return p;
+        }
+    }
+
+    /**
+     * Nodes each maintain an item and handle waits and signals for
+     * getting and setting it. The class extends
+     * AbstractQueuedSynchronizer to manage blocking, using AQS state
+     *  0 for waiting, 1 for ack, -1 for cancelled.
+     */
+    static final class Node extends AbstractQueuedSynchronizer {
+        /** Synchronization state value representing that node acked */
+        private static final int ACK    =  1;
+        /** Synchronization state value representing that node cancelled */
+        private static final int CANCEL = -1;
+
+        /** The item being transferred */
+        Object item;
+        /** Next node in wait queue */
+        Node next;
+
+        /** Creates a node with initial item */
+        Node(Object x) { item = x; }
+
+        /** Creates a node with initial item and next */
+        Node(Object x, Node n) { item = x; next = n; }
+
+        /**
+         * Implements AQS base acquire to succeed if not in WAITING state
+         */
+        protected boolean tryAcquire(int ignore) {
+            return getState() != 0;
+        }
+
+        /**
+         * Implements AQS base release to signal if state changed
+         */
+        protected boolean tryRelease(int newState) {
+            return compareAndSetState(0, newState);
+        }
+
+        /**
+         * Takes item and nulls out field (for sake of GC)
+         */
+        private Object extract() {
+            Object x = item;
+            item = null;
+            return x;
+        }
+
+        /**
+         * Tries to cancel on interrupt; if so rethrowing,
+         * else setting interrupt state
+         */
+        private void checkCancellationOnInterrupt(InterruptedException ie) 
+            throws InterruptedException {
+            if (release(CANCEL)) 
+                throw ie;
+            Thread.currentThread().interrupt();
+        }
+
+        /**
+         * Fills in the slot created by the consumer and signal consumer to
+         * continue.
+         */
+        boolean setItem(Object x) {
+            item = x; // can place in slot even if cancelled
+            return release(ACK);
+        }
+
+        /**
+         * Removes item from slot created by producer and signal producer
+         * to continue.
+         */
+        Object getItem() {
+            return (release(ACK))? extract() : null;
+        }
+
+        /**
+         * Waits for a consumer to take item placed by producer.
+         */
+        void waitForTake() throws InterruptedException {
+            try {
+                acquireInterruptibly(0);
+            } catch (InterruptedException ie) {
+                checkCancellationOnInterrupt(ie);
+            }
+        }
+
+        /**
+         * Waits for a producer to put item placed by consumer.
+         */
+        Object waitForPut() throws InterruptedException {
+            try {
+                acquireInterruptibly(0);
+            } catch (InterruptedException ie) {
+                checkCancellationOnInterrupt(ie);
+            }
+            return extract();
+        }
+
+        /**
+         * Waits for a consumer to take item placed by producer or time out.
+         */
+        boolean waitForTake(long nanos) throws InterruptedException {
+            try {
+                if (!tryAcquireNanos(0, nanos) &&
+                    release(CANCEL))
+                    return false;
+            } catch (InterruptedException ie) {
+                checkCancellationOnInterrupt(ie);
+            }
+            return true;
+        }
+
+        /**
+         * Waits for a producer to put item placed by consumer, or time out.
+         */
+        Object waitForPut(long nanos) throws InterruptedException {
+            try {
+                if (!tryAcquireNanos(0, nanos) &&
+                    release(CANCEL))
+                    return null;
+            } catch (InterruptedException ie) {
+                checkCancellationOnInterrupt(ie);
+            }
+            return extract();
+        }
+    }
+
+    /**
+     * Adds the specified element to this queue, waiting if necessary for
+     * another thread to receive it.
+     * @param o the element to add
+     * @throws InterruptedException if interrupted while waiting.
+     * @throws NullPointerException if the specified element is <tt>null</tt>.
+     */
+    public void put(E o) throws InterruptedException {
+        if (o == null) throw new NullPointerException();
+        final ReentrantLock qlock = this.qlock;
+
+        for (;;) {
+            Node node;
+            boolean mustWait;
+            if (Thread.interrupted()) throw new InterruptedException();
+            qlock.lock();
+            try {
+                node = waitingConsumers.deq();
+                if ( (mustWait = (node == null)) )
+                    node = waitingProducers.enq(o);
+            } finally {
+                qlock.unlock();
+            }
+
+            if (mustWait) {
+                node.waitForTake();
+                return;
+            }
+
+            else if (node.setItem(o))
+                return;
+
+            // else consumer cancelled, so retry
+        }
+    }
+
+    /**
+     * Inserts the specified element into this queue, waiting if necessary
+     * up to the specified wait time for another thread to receive it.
+     * @param o the element to add
+     * @param timeout how long to wait before giving up, in units of
+     * <tt>unit</tt>
+     * @param unit a <tt>TimeUnit</tt> determining how to interpret the
+     * <tt>timeout</tt> parameter
+     * @return <tt>true</tt> if successful, or <tt>false</tt> if
+     * the specified waiting time elapses before a consumer appears.
+     * @throws InterruptedException if interrupted while waiting.
+     * @throws NullPointerException if the specified element is <tt>null</tt>.
+     */
+    public boolean offer(E o, long timeout, TimeUnit unit) throws InterruptedException {
+        if (o == null) throw new NullPointerException();
+        long nanos = unit.toNanos(timeout);
+        final ReentrantLock qlock = this.qlock;
+        for (;;) {
+            Node node;
+            boolean mustWait;
+            if (Thread.interrupted()) throw new InterruptedException();
+            qlock.lock();
+            try {
+                node = waitingConsumers.deq();
+                if ( (mustWait = (node == null)) )
+                    node = waitingProducers.enq(o);
+            } finally {
+                qlock.unlock();
+            }
+
+            if (mustWait) 
+                return node.waitForTake(nanos);
+
+            else if (node.setItem(o))
+                return true;
+
+            // else consumer cancelled, so retry
+        }
+    }
+
+    /**
+     * Retrieves and removes the head of this queue, waiting if necessary
+     * for another thread to insert it.
+     * @throws InterruptedException if interrupted while waiting.
+     * @return the head of this queue
+     */
+    public E take() throws InterruptedException {
+        final ReentrantLock qlock = this.qlock;
+        for (;;) {
+            Node node;
+            boolean mustWait;
+
+            if (Thread.interrupted()) throw new InterruptedException();
+            qlock.lock();
+            try {
+                node = waitingProducers.deq();
+                if ( (mustWait = (node == null)) )
+                    node = waitingConsumers.enq(null);
+            } finally {
+                qlock.unlock();
+            }
+
+            if (mustWait) {
+                Object x = node.waitForPut();
+                return (E)x;
+            }
+            else {
+                Object x = node.getItem();
+                if (x != null)
+                    return (E)x;
+                // else cancelled, so retry
+            }
+        }
+    }
+
+    /**
+     * Retrieves and removes the head of this queue, waiting
+     * if necessary up to the specified wait time, for another thread
+     * to insert it.
+     * @param timeout how long to wait before giving up, in units of
+     * <tt>unit</tt>
+     * @param unit a <tt>TimeUnit</tt> determining how to interpret the
+     * <tt>timeout</tt> parameter
+     * @return the head of this queue, or <tt>null</tt> if the
+     * specified waiting time elapses before an element is present.
+     * @throws InterruptedException if interrupted while waiting.
+     */
+    public E poll(long timeout, TimeUnit unit) throws InterruptedException {
+        long nanos = unit.toNanos(timeout);
+        final ReentrantLock qlock = this.qlock;
+
+        for (;;) {
+            Node node;
+            boolean mustWait;
+
+            if (Thread.interrupted()) throw new InterruptedException();
+            qlock.lock();
+            try {
+                node = waitingProducers.deq();
+                if ( (mustWait = (node == null)) )
+                    node = waitingConsumers.enq(null);
+            } finally {
+                qlock.unlock();
+            }
+
+            if (mustWait) {
+                Object x = node.waitForPut(nanos);
+                return (E)x;
+            }
+            else {
+                Object x = node.getItem();
+                if (x != null)
+                    return (E)x;
+                // else cancelled, so retry
+            }
+        }
+    }
+
+    // Untimed nonblocking versions
+
+   /**
+    * Inserts the specified element into this queue, if another thread is
+    * waiting to receive it.
+    *
+    * @param o the element to add.
+    * @return <tt>true</tt> if it was possible to add the element to
+    *         this queue, else <tt>false</tt>
+    * @throws NullPointerException if the specified element is <tt>null</tt>
+    */
+    public boolean offer(E o) {
+        if (o == null) throw new NullPointerException();
+        final ReentrantLock qlock = this.qlock;
+
+        for (;;) {
+            Node node;
+            qlock.lock();
+            try {
+                node = waitingConsumers.deq();
+            } finally {
+                qlock.unlock();
+            }
+            if (node == null)
+                return false;
+
+            else if (node.setItem(o))
+                return true;
+            // else retry
+        }
+    }
+
+    /**
+     * Retrieves and removes the head of this queue, if another thread
+     * is currently making an element available.
+     *
+     * @return the head of this queue, or <tt>null</tt> if no
+     *         element is available.
+     */
+    public E poll() {
+        final ReentrantLock qlock = this.qlock;
+        for (;;) {
+            Node node;
+            qlock.lock();
+            try {
+                node = waitingProducers.deq();
+            } finally {
+                qlock.unlock();
+            }
+            if (node == null)
+                return null;
+
+            else {
+                Object x = node.getItem();
+                if (x != null)
+                    return (E)x;
+                // else retry
+            }
+        }
+    }
+
+    /**
+     * Always returns <tt>true</tt>. 
+     * A <tt>SynchronousQueue</tt> has no internal capacity.
+     * @return <tt>true</tt>
+     */
+    public boolean isEmpty() {
+        return true;
+    }
+
+    /**
+     * Always returns zero.
+     * A <tt>SynchronousQueue</tt> has no internal capacity.
+     * @return zero.
+     */
+    public int size() {
+        return 0;
+    }
+
+    /**
+     * Always returns zero.
+     * A <tt>SynchronousQueue</tt> has no internal capacity.
+     * @return zero.
+     */
+    public int remainingCapacity() {
+        return 0;
+    }
+
+    /**
+     * Does nothing.
+     * A <tt>SynchronousQueue</tt> has no internal capacity.
+     */
+    public void clear() {}
+
+    /**
+     * Always returns <tt>false</tt>.
+     * A <tt>SynchronousQueue</tt> has no internal capacity.
+     * @param o the element
+     * @return <tt>false</tt>
+     */
+    public boolean contains(Object o) {
+        return false;
+    }
+
+    /**
+     * Always returns <tt>false</tt>.
+     * A <tt>SynchronousQueue</tt> has no internal capacity.
+     *
+     * @param o the element to remove
+     * @return <tt>false</tt>
+     */
+    public boolean remove(Object o) {
+        return false;
+    }
+
+    /**
+     * Returns <tt>false</tt> unless given collection is empty.
+     * A <tt>SynchronousQueue</tt> has no internal capacity.
+     * @param c the collection
+     * @return <tt>false</tt> unless given collection is empty
+     */
+    public boolean containsAll(Collection<?> c) {
+        return c.isEmpty();
+    }
+
+    /**
+     * Always returns <tt>false</tt>.
+     * A <tt>SynchronousQueue</tt> has no internal capacity.
+     * @param c the collection
+     * @return <tt>false</tt>
+     */
+    public boolean removeAll(Collection<?> c) {
+        return false;
+    }
+
+    /**
+     * Always returns <tt>false</tt>.
+     * A <tt>SynchronousQueue</tt> has no internal capacity.
+     * @param c the collection
+     * @return <tt>false</tt>
+     */
+    public boolean retainAll(Collection<?> c) {
+        return false;
+    }
+
+    /**
+     * Always returns <tt>null</tt>. 
+     * A <tt>SynchronousQueue</tt> does not return elements
+     * unless actively waited on.
+     * @return <tt>null</tt>
+     */
+    public E peek() {
+        return null;
+    }
+
+
+    static class EmptyIterator<E> implements Iterator<E> {
+        public boolean hasNext() {
+            return false;
+        }
+        public E next() {
+            throw new NoSuchElementException();
+        }
+        public void remove() {
+            throw new IllegalStateException();
+        }
+    }
+
+    /**
+     * Returns an empty iterator in which <tt>hasNext</tt> always returns
+     * <tt>false</tt>.
+     *
+     * @return an empty iterator
+     */
+    public Iterator<E> iterator() {
+        return new EmptyIterator<E>();
+    }
+
+
+    /**
+     * Returns a zero-length array.
+     * @return a zero-length array
+     */
+    public Object[] toArray() {
+        return new Object[0];
+    }
+
+    /**
+     * Sets the zeroeth element of the specified array to <tt>null</tt>
+     * (if the array has non-zero length) and returns it.
+     * @param a the array
+     * @return the specified array
+     */
+    public <T> T[] toArray(T[] a) {
+        if (a.length > 0)
+            a[0] = null;
+        return a;
+    }
+
+
+    public int drainTo(Collection<? super E> c) {
+        if (c == null)
+            throw new NullPointerException();
+        if (c == this)
+            throw new IllegalArgumentException();
+        int n = 0;
+        E e;
+        while ( (e = poll()) != null) {
+            c.add(e);
+            ++n;
+        }
+        return n;
+    }
+
+    public int drainTo(Collection<? super E> c, int maxElements) {
+        if (c == null)
+            throw new NullPointerException();
+        if (c == this)
+            throw new IllegalArgumentException();
+        int n = 0;
+        E e;
+        while (n < maxElements && (e = poll()) != null) {
+            c.add(e);
+            ++n;
+        }
+        return n;
+    }
+}
+
+
+
+
+

Propchange: incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/SynchronousQueue.java
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    svn:eol-style = native

Added: incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/ThreadFactory.java
URL: http://svn.apache.org/viewvc/incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/ThreadFactory.java?rev=421111&view=auto
==============================================================================
--- incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/ThreadFactory.java (added)
+++ incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/ThreadFactory.java Tue Jul 11 21:12:04 2006
@@ -0,0 +1,40 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent;
+
+/**
+ * An object that creates new threads on demand.  Using thread factories
+ * removes hardwiring of calls to {@link Thread#Thread(Runnable) new Thread},
+ * enabling applications to use special thread subclasses, priorities, etc.
+ *
+ * <p> 
+ * The simplest implementation of this interface is just:
+ * <pre>
+ * class SimpleThreadFactory implements ThreadFactory {
+ *   public Thread newThread(Runnable r) {
+ *     return new Thread(r);
+ *   }
+ * }
+ * </pre>
+ *
+ * The {@link Executors#defaultThreadFactory} method provides a more
+ * useful simple implementation, that sets the created thread context
+ * to known values before returning it. 
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface ThreadFactory { 
+
+    /**
+     * Constructs a new <tt>Thread</tt>.  Implementations may also initialize
+     * priority, name, daemon status, <tt>ThreadGroup</tt>, etc.
+     *
+     * @param r a runnable to be executed by new thread instance
+     * @return constructed thread
+     */
+    Thread newThread(Runnable r);
+}

Propchange: incubator/harmony/enhanced/classlib/trunk/sandbox/juc-proposal/concurrent/src/main/java/java/util/concurrent/ThreadFactory.java
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    svn:eol-style = native



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