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root/jsr166/jsr166/src/jsr166y/LinkedTransferQueue.java

Comparing jsr166/src/jsr166y/LinkedTransferQueue.java (file contents):
Revision 1.27 by jsr166, Sun Jul 26 05:55:34 2009 UTC vs.
Revision 1.39 by jsr166, Fri Jul 31 20:24:30 2009 UTC

#	Line 10 | Line 10 | import java.util.concurrent.*;
10
11		import java.util.AbstractQueue;
12		import java.util.Collection;
13	+	import java.util.ConcurrentModificationException;
14		import java.util.Iterator;
15		import java.util.NoSuchElementException;
16	+	import java.util.Queue;
17		import java.util.concurrent.locks.LockSupport;
18		import java.util.concurrent.atomic.AtomicReference;
17	–	import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
19
20		/**
21		* An unbounded {@linkplain TransferQueue} based on linked nodes.
#	Line 115 | Line 116 | public class LinkedTransferQueue<E> exte
116		this.isData = isData;
117		}
118
119	<	@SuppressWarnings("rawtypes")
120	<	static final AtomicReferenceFieldUpdater<Node, Node>
121	<	nextUpdater = AtomicReferenceFieldUpdater.newUpdater
122	<	(Node.class, Node.class, "next");
119	>	// Unsafe mechanics
120	>
121	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
122	>	private static final long nextOffset =
123	>	objectFieldOffset(UNSAFE, "next", Node.class);
124
125		final boolean casNext(Node<E> cmp, Node<E> val) {
126	<	return nextUpdater.compareAndSet(this, cmp, val);
126	>	return UNSAFE.compareAndSwapObject(this, nextOffset, cmp, val);
127		}
128
129		final void clearNext() {
130	<	nextUpdater.lazySet(this, this);
130	>	UNSAFE.putOrderedObject(this, nextOffset, this);
131	>	}
132	>
133	>	/**
134	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
135	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
136	>	* into a jdk.
137	>	*
138	>	* @return a sun.misc.Unsafe
139	>	*/
140	>	private static sun.misc.Unsafe getUnsafe() {
141	>	try {
142	>	return sun.misc.Unsafe.getUnsafe();
143	>	} catch (SecurityException se) {
144	>	try {
145	>	return java.security.AccessController.doPrivileged
146	>	(new java.security
147	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
148	>	public sun.misc.Unsafe run() throws Exception {
149	>	java.lang.reflect.Field f = sun.misc
150	>	.Unsafe.class.getDeclaredField("theUnsafe");
151	>	f.setAccessible(true);
152	>	return (sun.misc.Unsafe) f.get(null);
153	>	}});
154	>	} catch (java.security.PrivilegedActionException e) {
155	>	throw new RuntimeException("Could not initialize intrinsics",
156	>	e.getCause());
157	>	}
158	>	}
159		}
160
161		private static final long serialVersionUID = -3375979862319811754L;
#	Line 264 | Line 294 | public class LinkedTransferQueue<E> exte
294		* @param e the comparison value for checking match
295		* @param mode mode
296		* @param nanos timeout value
297	<	* @return matched item, or s if cancelled
297	>	* @return matched item, or null if cancelled
298		*/
299		private E awaitFulfill(Node<E> pred, Node<E> s, E e,
300		int mode, long nanos) {
#	Line 330 | Line 360 | public class LinkedTransferQueue<E> exte
360		for (;;) {
361		Node<E> h = head.get();
362		Node<E> first = h.next;
363	<	if (first != null && first.next == first) { // help advance
363	>	if (first != null && first.get() == first) { // help advance
364		advanceHead(h, first);
365		continue;
366		}
#	Line 442 | Line 472 | public class LinkedTransferQueue<E> exte
472		addAll(c);
473		}
474
475	<	public void put(E e) throws InterruptedException {
476	<	if (e == null) throw new NullPointerException();
477	<	if (Thread.interrupted()) throw new InterruptedException();
478	<	xfer(e, NOWAIT, 0);
475	>	/**
476	>	* Inserts the specified element at the tail of this queue.
477	>	* As the queue is unbounded, this method will never block.
478	>	*
479	>	* @throws NullPointerException if the specified element is null
480	>	*/
481	>	public void put(E e) {
482	>	offer(e);
483		}
484
485	<	public boolean offer(E e, long timeout, TimeUnit unit)
486	<	throws InterruptedException {
487	<	if (e == null) throw new NullPointerException();
488	<	if (Thread.interrupted()) throw new InterruptedException();
489	<	xfer(e, NOWAIT, 0);
490	<	return true;
485	>	/**
486	>	* Inserts the specified element at the tail of this queue.
487	>	* As the queue is unbounded, this method will never block or
488	>	* return {@code false}.
489	>	*
490	>	* @return {@code true} (as specified by
491	>	*  {@link BlockingQueue#offer(Object,long,TimeUnit) BlockingQueue.offer})
492	>	* @throws NullPointerException if the specified element is null
493	>	*/
494	>	public boolean offer(E e, long timeout, TimeUnit unit) {
495	>	return offer(e);
496		}
497
498	+	/**
499	+	* Inserts the specified element at the tail of this queue.
500	+	* As the queue is unbounded, this method will never return {@code false}.
501	+	*
502	+	* @return {@code true} (as specified by
503	+	*         {@link BlockingQueue#offer(Object) BlockingQueue.offer})
504	+	* @throws NullPointerException if the specified element is null
505	+	*/
506		public boolean offer(E e) {
507		if (e == null) throw new NullPointerException();
508		xfer(e, NOWAIT, 0);
509		return true;
510		}
511
512	+	/**
513	+	* Inserts the specified element at the tail of this queue.
514	+	* As the queue is unbounded, this method will never throw
515	+	* {@link IllegalStateException} or return {@code false}.
516	+	*
517	+	* @return {@code true} (as specified by {@link Collection#add})
518	+	* @throws NullPointerException if the specified element is null
519	+	*/
520		public boolean add(E e) {
521	+	return offer(e);
522	+	}
523	+
524	+	/**
525	+	* Transfers the specified element immediately if there exists a
526	+	* consumer already waiting to receive it (in {@link #take} or
527	+	* timed {@link #poll(long,TimeUnit) poll}), otherwise
528	+	* returning {@code false} without enqueuing the element.
529	+	*
530	+	* @throws NullPointerException if the specified element is null
531	+	*/
532	+	public boolean tryTransfer(E e) {
533		if (e == null) throw new NullPointerException();
534	<	xfer(e, NOWAIT, 0);
468	<	return true;
534	>	return fulfill(e) != null;
535		}
536
537	+	/**
538	+	* Inserts the specified element at the tail of this queue,
539	+	* waiting if necessary for the element to be received by a
540	+	* consumer invoking {@code take} or {@code poll}.
541	+	*
542	+	* @throws NullPointerException if the specified element is null
543	+	*/
544		public void transfer(E e) throws InterruptedException {
545		if (e == null) throw new NullPointerException();
546		if (xfer(e, WAIT, 0) == null) {
#	Line 476 | Line 549 | public class LinkedTransferQueue<E> exte
549		}
550		}
551
552	+	/**
553	+	* Inserts the specified element at the tail of this queue,
554	+	* waiting up to the specified wait time if necessary for the
555	+	* element to be received by a consumer invoking {@code take} or
556	+	* {@code poll}.
557	+	*
558	+	* @throws NullPointerException if the specified element is null
559	+	*/
560		public boolean tryTransfer(E e, long timeout, TimeUnit unit)
561		throws InterruptedException {
562		if (e == null) throw new NullPointerException();
#	Line 486 | Line 567 | public class LinkedTransferQueue<E> exte
567		throw new InterruptedException();
568		}
569
489	–	public boolean tryTransfer(E e) {
490	–	if (e == null) throw new NullPointerException();
491	–	return fulfill(e) != null;
492	–	}
493	–
570		public E take() throws InterruptedException {
571	<	Object e = xfer(null, WAIT, 0);
571	>	E e = xfer(null, WAIT, 0);
572		if (e != null)
573	<	return (E) e;
573	>	return e;
574		Thread.interrupted();
575		throw new InterruptedException();
576		}
577
578		public E poll(long timeout, TimeUnit unit) throws InterruptedException {
579	<	Object e = xfer(null, TIMEOUT, unit.toNanos(timeout));
579	>	E e = xfer(null, TIMEOUT, unit.toNanos(timeout));
580		if (e != null || !Thread.interrupted())
581	<	return (E) e;
581	>	return e;
582		throw new InterruptedException();
583		}
584
#	Line 510 | Line 586 | public class LinkedTransferQueue<E> exte
586		return fulfill(null);
587		}
588
589	+	/**
590	+	* @throws NullPointerException     {@inheritDoc}
591	+	* @throws IllegalArgumentException {@inheritDoc}
592	+	*/
593		public int drainTo(Collection<? super E> c) {
594		if (c == null)
595		throw new NullPointerException();
#	Line 524 | Line 604 | public class LinkedTransferQueue<E> exte
604		return n;
605		}
606
607	+	/**
608	+	* @throws NullPointerException     {@inheritDoc}
609	+	* @throws IllegalArgumentException {@inheritDoc}
610	+	*/
611		public int drainTo(Collection<? super E> c, int maxElements) {
612		if (c == null)
613		throw new NullPointerException();
#	Line 568 | Line 652 | public class LinkedTransferQueue<E> exte
652		}
653		}
654
655	<
655	>	/**
656	>	* Returns an iterator over the elements in this queue in proper
657	>	* sequence, from head to tail.
658	>	*
659	>	* <p>The returned iterator is a "weakly consistent" iterator that
660	>	* will never throw
661	>	* {@link ConcurrentModificationException ConcurrentModificationException},
662	>	* and guarantees to traverse elements as they existed upon
663	>	* construction of the iterator, and may (but is not guaranteed
664	>	* to) reflect any modifications subsequent to construction.
665	>	*
666	>	* @return an iterator over the elements in this queue in proper sequence
667	>	*/
668		public Iterator<E> iterator() {
669		return new Itr();
670		}
#	Line 583 | Line 679 | public class LinkedTransferQueue<E> exte
679		class Itr implements Iterator<E> {
680		Node<E> next;        // node to return next
681		Node<E> pnext;       // predecessor of next
586	–	Node<E> snext;       // successor of next
682		Node<E> curr;        // last returned node, for remove()
683		Node<E> pcurr;       // predecessor of curr, for remove()
684	<	E nextItem;        // Cache of next item, once committed to in next
684	>	E nextItem;          // Cache of next item, once committed to in next
685
686		Itr() {
687	<	findNext();
687	>	advance();
688		}
689
690		/**
691	<	* Ensures next points to next valid node, or null if none.
691	>	* Moves to next valid node and returns item to return for
692	>	* next(), or null if no such.
693		*/
694	<	void findNext() {
694	>	private E advance() {
695	>	pcurr = pnext;
696	>	curr = next;
697	>	E item = nextItem;
698	>
699		for (;;) {
700	<	Node<E> pred = pnext;
701	<	Node<E> q = next;
702	<	if (pred == null || pred == q) {
603	<	pred = traversalHead();
604	<	q = pred.next;
605	<	}
606	<	if (q == null || !q.isData) {
700	>	pnext = (next == null) ? traversalHead() : next;
701	>	next = pnext.next;
702	>	if (next == pnext) {
703		next = null;
704	<	return;
704	>	continue;  // restart
705		}
706	<	Object x = q.get();
707	<	Node<E> s = q.next;
708	<	if (x != null && q != x && q != s) {
706	>	if (next == null)
707	>	break;
708	>	Object x = next.get();
709	>	if (x != null && x != next) {
710		nextItem = (E) x;
711	<	snext = s;
615	<	pnext = pred;
616	<	next = q;
617	<	return;
711	>	break;
712		}
619	–	pnext = q;
620	–	next = s;
713		}
714	+	return item;
715		}
716
717		public boolean hasNext() {
#	Line 626 | Line 719 | public class LinkedTransferQueue<E> exte
719		}
720
721		public E next() {
722	<	if (next == null) throw new NoSuchElementException();
723	<	pcurr = pnext;
724	<	curr = next;
632	<	pnext = next;
633	<	next = snext;
634	<	E x = nextItem;
635	<	findNext();
636	<	return x;
722	>	if (next == null)
723	>	throw new NoSuchElementException();
724	>	return advance();
725		}
726
727		public void remove() {
#	Line 703 | Line 791 | public class LinkedTransferQueue<E> exte
791		* @return the number of elements in this queue
792		*/
793		public int size() {
794	<	int count = 0;
795	<	Node<E> h = traversalHead();
796	<	for (Node<E> p = h.next; p != null && p.isData; p = p.next) {
797	<	Object x = p.get();
798	<	if (x != null && x != p) {
799	<	if (++count == Integer.MAX_VALUE) // saturated
794	>	for (;;) {
795	>	int count = 0;
796	>	Node<E> pred = traversalHead();
797	>	for (;;) {
798	>	Node<E> q = pred.next;
799	>	if (q == pred) // restart
800		break;
801	+	if (q == null || !q.isData)
802	+	return count;
803	+	Object x = q.get();
804	+	if (x != null && x != q) {
805	+	if (++count == Integer.MAX_VALUE) // saturated
806	+	return count;
807	+	}
808	+	pred = q;
809		}
810		}
715	–	return count;
811		}
812
813		public int getWaitingConsumerCount() {
814	<	int count = 0;
815	<	Node<E> h = traversalHead();
816	<	for (Node<E> p = h.next; p != null && !p.isData; p = p.next) {
817	<	if (p.get() == null) {
818	<	if (++count == Integer.MAX_VALUE)
814	>	// converse of size -- count valid non-data nodes
815	>	for (;;) {
816	>	int count = 0;
817	>	Node<E> pred = traversalHead();
818	>	for (;;) {
819	>	Node<E> q = pred.next;
820	>	if (q == pred) // restart
821		break;
822	+	if (q == null || q.isData)
823	+	return count;
824	+	Object x = q.get();
825	+	if (x == null) {
826	+	if (++count == Integer.MAX_VALUE) // saturated
827	+	return count;
828	+	}
829	+	pred = q;
830		}
831		}
727	–	return count;
728	–	}
729	–
730	–	public int remainingCapacity() {
731	–	return Integer.MAX_VALUE;
832		}
833
834		public boolean remove(Object o) {
#	Line 738 | Line 838 | public class LinkedTransferQueue<E> exte
838		Node<E> pred = traversalHead();
839		for (;;) {
840		Node<E> q = pred.next;
741	–	if (q == null || !q.isData)
742	–	return false;
841		if (q == pred) // restart
842		break;
843	+	if (q == null || !q.isData)
844	+	return false;
845		Object x = q.get();
846		if (x != null && x != q && o.equals(x) &&
847		q.compareAndSet(x, q)) {
#	Line 754 | Line 854 | public class LinkedTransferQueue<E> exte
854		}
855
856		/**
857	+	* Always returns {@code Integer.MAX_VALUE} because a
858	+	* {@code LinkedTransferQueue} is not capacity constrained.
859	+	*
860	+	* @return {@code Integer.MAX_VALUE} (as specified by
861	+	*         {@link BlockingQueue#remainingCapacity()})
862	+	*/
863	+	public int remainingCapacity() {
864	+	return Integer.MAX_VALUE;
865	+	}
866	+
867	+	/**
868		* Save the state to a stream (that is, serialize it).
869		*
870		* @serialData All of the elements (each an {@code E}) in
#	Line 799 | Line 910 | public class LinkedTransferQueue<E> exte
910		new PaddedAtomicReference<Node<E>>(null));
911		}
912
913	<	// Unsafe mechanics for jsr166y 3rd party package.
913	>	// Unsafe mechanics
914	>
915	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
916	>	private static final long headOffset =
917	>	objectFieldOffset(UNSAFE, "head", LinkedTransferQueue.class);
918	>	private static final long tailOffset =
919	>	objectFieldOffset(UNSAFE, "tail", LinkedTransferQueue.class);
920	>	private static final long cleanMeOffset =
921	>	objectFieldOffset(UNSAFE, "cleanMe", LinkedTransferQueue.class);
922	>
923	>
924	>	static long objectFieldOffset(sun.misc.Unsafe UNSAFE,
925	>	String field, Class<?> klazz) {
926	>	try {
927	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
928	>	} catch (NoSuchFieldException e) {
929	>	// Convert Exception to corresponding Error
930	>	NoSuchFieldError error = new NoSuchFieldError(field);
931	>	error.initCause(e);
932	>	throw error;
933	>	}
934	>	}
935	>
936	>	/**
937	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
938	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
939	>	* into a jdk.
940	>	*
941	>	* @return a sun.misc.Unsafe
942	>	*/
943		private static sun.misc.Unsafe getUnsafe() {
944		try {
945		return sun.misc.Unsafe.getUnsafe();
946		} catch (SecurityException se) {
947		try {
948		return java.security.AccessController.doPrivileged
949	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
949	>	(new java.security
950	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
951		public sun.misc.Unsafe run() throws Exception {
952	<	return getUnsafeByReflection();
952	>	java.lang.reflect.Field f = sun.misc
953	>	.Unsafe.class.getDeclaredField("theUnsafe");
954	>	f.setAccessible(true);
955	>	return (sun.misc.Unsafe) f.get(null);
956		}});
957		} catch (java.security.PrivilegedActionException e) {
958		throw new RuntimeException("Could not initialize intrinsics",
#	Line 816 | Line 960 | public class LinkedTransferQueue<E> exte
960		}
961		}
962		}
819	–
820	–	private static sun.misc.Unsafe getUnsafeByReflection()
821	–	throws NoSuchFieldException, IllegalAccessException {
822	–	java.lang.reflect.Field f =
823	–	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
824	–	f.setAccessible(true);
825	–	return (sun.misc.Unsafe) f.get(null);
826	–	}
827	–
828	–	private static long fieldOffset(String fieldName, Class<?> klazz) {
829	–	try {
830	–	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
831	–	} catch (NoSuchFieldException e) {
832	–	// Convert Exception to Error
833	–	NoSuchFieldError error = new NoSuchFieldError(fieldName);
834	–	error.initCause(e);
835	–	throw error;
836	–	}
837	–	}
838	–
839	–	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
840	–	private static final long headOffset =
841	–	fieldOffset("head", LinkedTransferQueue.class);
842	–	private static final long tailOffset =
843	–	fieldOffset("tail", LinkedTransferQueue.class);
844	–	private static final long cleanMeOffset =
845	–	fieldOffset("cleanMe", LinkedTransferQueue.class);
846	–
963		}

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