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

Comparing jsr166/src/jsr166y/LinkedTransferQueue.java (file contents):
Revision 1.30 by jsr166, Mon Jul 27 03:22:39 2009 UTC vs.
Revision 1.44 by jsr166, Tue Aug 4 20:32:16 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.
21	>	* An unbounded {@link TransferQueue} based on linked nodes.
22		* This queue orders elements FIFO (first-in-first-out) with respect
23		* to any given producer.  The <em>head</em> of the queue is that
24		* element that has been on the queue the longest time for some
#	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 189 | Line 219 | public class LinkedTransferQueue<E> exte
219		Node<E> t = tail.get();
220		Node<E> h = head.get();
221
222	<	if (t != null && (t == h || t.isData == isData)) {
222	>	if (t == h || t.isData == isData) {
223		if (s == null)
224		s = new Node<E>(e, isData);
225		Node<E> last = t.next;
#	Line 201 | Line 231 | public class LinkedTransferQueue<E> exte
231		tail.compareAndSet(t, s);
232		return awaitFulfill(t, s, e, mode, nanos);
233		}
234	<	}
205	<
206	<	else if (h != null) {
234	>	} else {
235		Node<E> first = h.next;
236		if (t == tail.get() && first != null &&
237		advanceHead(h, first)) {
#	Line 231 | Line 259 | public class LinkedTransferQueue<E> exte
259		Node<E> t = tail.get();
260		Node<E> h = head.get();
261
262	<	if (t != null && (t == h || t.isData == isData)) {
262	>	if (t == h || t.isData == isData) {
263		Node<E> last = t.next;
264		if (t == tail.get()) {
265		if (last != null)
#	Line 239 | Line 267 | public class LinkedTransferQueue<E> exte
267		else
268		return null;
269		}
270	<	}
243	<	else if (h != null) {
270	>	} else {
271		Node<E> first = h.next;
272		if (t == tail.get() &&
273		first != null &&
#	Line 264 | Line 291 | public class LinkedTransferQueue<E> exte
291		* @param e the comparison value for checking match
292		* @param mode mode
293		* @param nanos timeout value
294	<	* @return matched item, or s if cancelled
294	>	* @return matched item, or null if cancelled
295		*/
296		private E awaitFulfill(Node<E> pred, Node<E> s, E e,
297		int mode, long nanos) {
#	Line 302 | Line 329 | public class LinkedTransferQueue<E> exte
329		}
330		if (spins < 0) {
331		Node<E> h = head.get(); // only spin if at head
332	<	spins = ((h != null && h.next == s) ?
333	<	((mode == TIMEOUT) ?
334	<	maxTimedSpins : maxUntimedSpins) : 0);
332	>	spins = ((h.next != s) ? 0 :
333	>	(mode == TIMEOUT) ? maxTimedSpins :
334	>	maxUntimedSpins);
335		}
336		if (spins > 0)
337		--spins;
#	Line 330 | Line 357 | public class LinkedTransferQueue<E> exte
357		for (;;) {
358		Node<E> h = head.get();
359		Node<E> first = h.next;
360	<	if (first != null && first.next == first) { // help advance
360	>	if (first != null && first.get() == first) { // help advance
361		advanceHead(h, first);
362		continue;
363		}
#	Line 443 | Line 470 | public class LinkedTransferQueue<E> exte
470		}
471
472		/**
473	<	* @throws InterruptedException {@inheritDoc}
474	<	* @throws NullPointerException {@inheritDoc}
473	>	* Inserts the specified element at the tail of this queue.
474	>	* As the queue is unbounded, this method will never block.
475	>	*
476	>	* @throws NullPointerException if the specified element is null
477		*/
478	<	public void put(E e) throws InterruptedException {
479	<	if (e == null) throw new NullPointerException();
451	<	if (Thread.interrupted()) throw new InterruptedException();
452	<	xfer(e, NOWAIT, 0);
478	>	public void put(E e) {
479	>	offer(e);
480		}
481
482		/**
483	<	* @throws InterruptedException {@inheritDoc}
484	<	* @throws NullPointerException {@inheritDoc}
483	>	* Inserts the specified element at the tail of this queue.
484	>	* As the queue is unbounded, this method will never block or
485	>	* return {@code false}.
486	>	*
487	>	* @return {@code true} (as specified by
488	>	*  {@link BlockingQueue#offer(Object,long,TimeUnit) BlockingQueue.offer})
489	>	* @throws NullPointerException if the specified element is null
490		*/
491	<	public boolean offer(E e, long timeout, TimeUnit unit)
492	<	throws InterruptedException {
461	<	if (e == null) throw new NullPointerException();
462	<	if (Thread.interrupted()) throw new InterruptedException();
463	<	xfer(e, NOWAIT, 0);
464	<	return true;
491	>	public boolean offer(E e, long timeout, TimeUnit unit) {
492	>	return offer(e);
493		}
494
495		/**
496	<	* @throws NullPointerException {@inheritDoc}
496	>	* Inserts the specified element at the tail of this queue.
497	>	* As the queue is unbounded, this method will never return {@code false}.
498	>	*
499	>	* @return {@code true} (as specified by
500	>	*         {@link BlockingQueue#offer(Object) BlockingQueue.offer})
501	>	* @throws NullPointerException if the specified element is null
502		*/
503		public boolean offer(E e) {
504		if (e == null) throw new NullPointerException();
#	Line 474 | Line 507 | public class LinkedTransferQueue<E> exte
507		}
508
509		/**
510	<	* @throws NullPointerException {@inheritDoc}
510	>	* Inserts the specified element at the tail of this queue.
511	>	* As the queue is unbounded, this method will never throw
512	>	* {@link IllegalStateException} or return {@code false}.
513	>	*
514	>	* @return {@code true} (as specified by {@link Collection#add})
515	>	* @throws NullPointerException if the specified element is null
516		*/
517		public boolean add(E e) {
518	+	return offer(e);
519	+	}
520	+
521	+	/**
522	+	* Transfers the element to a waiting consumer immediately, if possible.
523	+	*
524	+	* <p>More precisely, transfers the specified element immediately
525	+	* if there exists a consumer already waiting to receive it (in
526	+	* {@link #take} or timed {@link #poll(long,TimeUnit) poll}),
527	+	* otherwise returning {@code false} without enqueuing the element.
528	+	*
529	+	* @throws NullPointerException if the specified element is null
530	+	*/
531	+	public boolean tryTransfer(E e) {
532		if (e == null) throw new NullPointerException();
533	<	xfer(e, NOWAIT, 0);
482	<	return true;
533	>	return fulfill(e) != null;
534		}
535
536		/**
537	<	* @throws InterruptedException {@inheritDoc}
538	<	* @throws NullPointerException {@inheritDoc}
537	>	* Transfers the element to a consumer, waiting if necessary to do so.
538	>	*
539	>	* <p>More precisely, transfers the specified element immediately
540	>	* if there exists a consumer already waiting to receive it (in
541	>	* {@link #take} or timed {@link #poll(long,TimeUnit) poll}),
542	>	* else inserts the specified element at the tail of this queue
543	>	* and waits until the element is received by a consumer.
544	>	*
545	>	* @throws NullPointerException if the specified element is null
546		*/
547		public void transfer(E e) throws InterruptedException {
548		if (e == null) throw new NullPointerException();
#	Line 495 | Line 553 | public class LinkedTransferQueue<E> exte
553		}
554
555		/**
556	<	* @throws InterruptedException {@inheritDoc}
557	<	* @throws NullPointerException {@inheritDoc}
556	>	* Transfers the element to a consumer if it is possible to do so
557	>	* before the timeout elapses.
558	>	*
559	>	* <p>More precisely, transfers the specified element immediately
560	>	* if there exists a consumer already waiting to receive it (in
561	>	* {@link #take} or timed {@link #poll(long,TimeUnit) poll}),
562	>	* else inserts the specified element at the tail of this queue
563	>	* and waits until the element is received by a consumer,
564	>	* returning {@code false} if the specified wait time elapses
565	>	* before the element can be transferred.
566	>	*
567	>	* @throws NullPointerException if the specified element is null
568		*/
569		public boolean tryTransfer(E e, long timeout, TimeUnit unit)
570		throws InterruptedException {
#	Line 508 | Line 576 | public class LinkedTransferQueue<E> exte
576		throw new InterruptedException();
577		}
578
511	–	/**
512	–	* @throws NullPointerException {@inheritDoc}
513	–	*/
514	–	public boolean tryTransfer(E e) {
515	–	if (e == null) throw new NullPointerException();
516	–	return fulfill(e) != null;
517	–	}
518	–
519	–	/**
520	–	* @throws InterruptedException {@inheritDoc}
521	–	*/
579		public E take() throws InterruptedException {
580	<	Object e = xfer(null, WAIT, 0);
580	>	E e = xfer(null, WAIT, 0);
581		if (e != null)
582	<	return (E) e;
582	>	return e;
583		Thread.interrupted();
584		throw new InterruptedException();
585		}
586
530	–	/**
531	–	* @throws InterruptedException {@inheritDoc}
532	–	*/
587		public E poll(long timeout, TimeUnit unit) throws InterruptedException {
588	<	Object e = xfer(null, TIMEOUT, unit.toNanos(timeout));
588	>	E e = xfer(null, TIMEOUT, unit.toNanos(timeout));
589		if (e != null || !Thread.interrupted())
590	<	return (E) e;
590	>	return e;
591		throw new InterruptedException();
592		}
593
#	Line 586 | Line 640 | public class LinkedTransferQueue<E> exte
640		for (;;) {
641		Node<E> t = tail.get();
642		Node<E> h = head.get();
643	<	if (h != null && t != null) {
644	<	Node<E> last = t.next;
645	<	Node<E> first = h.next;
646	<	if (t == tail.get()) {
647	<	if (last != null)
648	<	tail.compareAndSet(t, last);
649	<	else if (first != null) {
650	<	Object x = first.get();
651	<	if (x == first)
598	<	advanceHead(h, first);
599	<	else
600	<	return h;
601	<	}
643	>	Node<E> last = t.next;
644	>	Node<E> first = h.next;
645	>	if (t == tail.get()) {
646	>	if (last != null)
647	>	tail.compareAndSet(t, last);
648	>	else if (first != null) {
649	>	Object x = first.get();
650	>	if (x == first)
651	>	advanceHead(h, first);
652		else
653		return h;
654		}
655	+	else
656	+	return h;
657		}
658		reclean();
659		}
660		}
661
662	<
662	>	/**
663	>	* Returns an iterator over the elements in this queue in proper
664	>	* sequence, from head to tail.
665	>	*
666	>	* <p>The returned iterator is a "weakly consistent" iterator that
667	>	* will never throw
668	>	* {@link ConcurrentModificationException ConcurrentModificationException},
669	>	* and guarantees to traverse elements as they existed upon
670	>	* construction of the iterator, and may (but is not guaranteed
671	>	* to) reflect any modifications subsequent to construction.
672	>	*
673	>	* @return an iterator over the elements in this queue in proper sequence
674	>	*/
675		public Iterator<E> iterator() {
676		return new Itr();
677		}
#	Line 622 | Line 686 | public class LinkedTransferQueue<E> exte
686		class Itr implements Iterator<E> {
687		Node<E> next;        // node to return next
688		Node<E> pnext;       // predecessor of next
625	–	Node<E> snext;       // successor of next
689		Node<E> curr;        // last returned node, for remove()
690		Node<E> pcurr;       // predecessor of curr, for remove()
691	<	E nextItem;        // Cache of next item, once committed to in next
691	>	E nextItem;          // Cache of next item, once committed to in next
692
693		Itr() {
694	<	findNext();
694	>	advance();
695		}
696
697		/**
698	<	* Ensures next points to next valid node, or null if none.
698	>	* Moves to next valid node and returns item to return for
699	>	* next(), or null if no such.
700		*/
701	<	void findNext() {
701	>	private E advance() {
702	>	pcurr = pnext;
703	>	curr = next;
704	>	E item = nextItem;
705	>
706		for (;;) {
707	<	Node<E> pred = pnext;
708	<	Node<E> q = next;
709	<	if (pred == null || pred == q) {
642	<	pred = traversalHead();
643	<	q = pred.next;
644	<	}
645	<	if (q == null || !q.isData) {
707	>	pnext = (next == null) ? traversalHead() : next;
708	>	next = pnext.next;
709	>	if (next == pnext) {
710		next = null;
711	<	return;
711	>	continue;  // restart
712		}
713	<	Object x = q.get();
714	<	Node<E> s = q.next;
715	<	if (x != null && q != x && q != s) {
713	>	if (next == null)
714	>	break;
715	>	Object x = next.get();
716	>	if (x != null && x != next) {
717		nextItem = (E) x;
718	<	snext = s;
654	<	pnext = pred;
655	<	next = q;
656	<	return;
718	>	break;
719		}
658	–	pnext = q;
659	–	next = s;
720		}
721	+	return item;
722		}
723
724		public boolean hasNext() {
#	Line 665 | Line 726 | public class LinkedTransferQueue<E> exte
726		}
727
728		public E next() {
729	<	if (next == null) throw new NoSuchElementException();
730	<	pcurr = pnext;
731	<	curr = next;
671	<	pnext = next;
672	<	next = snext;
673	<	E x = nextItem;
674	<	findNext();
675	<	return x;
729	>	if (next == null)
730	>	throw new NoSuchElementException();
731	>	return advance();
732		}
733
734		public void remove() {
#	Line 701 | Line 757 | public class LinkedTransferQueue<E> exte
757		}
758		}
759
760	+	/**
761	+	* Returns {@code true} if this queue contains no elements.
762	+	*
763	+	* @return {@code true} if this queue contains no elements
764	+	*/
765		public boolean isEmpty() {
766		for (;;) {
767		Node<E> h = traversalHead();
#	Line 742 | Line 803 | public class LinkedTransferQueue<E> exte
803		* @return the number of elements in this queue
804		*/
805		public int size() {
806	<	int count = 0;
807	<	Node<E> h = traversalHead();
808	<	for (Node<E> p = h.next; p != null && p.isData; p = p.next) {
809	<	Object x = p.get();
810	<	if (x != null && x != p) {
811	<	if (++count == Integer.MAX_VALUE) // saturated
806	>	for (;;) {
807	>	int count = 0;
808	>	Node<E> pred = traversalHead();
809	>	for (;;) {
810	>	Node<E> q = pred.next;
811	>	if (q == pred) // restart
812		break;
813	+	if (q == null || !q.isData)
814	+	return count;
815	+	Object x = q.get();
816	+	if (x != null && x != q) {
817	+	if (++count == Integer.MAX_VALUE) // saturated
818	+	return count;
819	+	}
820	+	pred = q;
821		}
822		}
754	–	return count;
823		}
824
825		public int getWaitingConsumerCount() {
826	<	int count = 0;
827	<	Node<E> h = traversalHead();
828	<	for (Node<E> p = h.next; p != null && !p.isData; p = p.next) {
829	<	if (p.get() == null) {
830	<	if (++count == Integer.MAX_VALUE)
826	>	// converse of size -- count valid non-data nodes
827	>	for (;;) {
828	>	int count = 0;
829	>	Node<E> pred = traversalHead();
830	>	for (;;) {
831	>	Node<E> q = pred.next;
832	>	if (q == pred) // restart
833		break;
834	+	if (q == null || q.isData)
835	+	return count;
836	+	Object x = q.get();
837	+	if (x == null) {
838	+	if (++count == Integer.MAX_VALUE) // saturated
839	+	return count;
840	+	}
841	+	pred = q;
842		}
843		}
766	–	return count;
767	–	}
768	–
769	–	public int remainingCapacity() {
770	–	return Integer.MAX_VALUE;
844		}
845
846	+	/**
847	+	* Removes a single instance of the specified element from this queue,
848	+	* if it is present.  More formally, removes an element {@code e} such
849	+	* that {@code o.equals(e)}, if this queue contains one or more such
850	+	* elements.
851	+	* Returns {@code true} if this queue contained the specified element
852	+	* (or equivalently, if this queue changed as a result of the call).
853	+	*
854	+	* @param o element to be removed from this queue, if present
855	+	* @return {@code true} if this queue changed as a result of the call
856	+	*/
857		public boolean remove(Object o) {
858		if (o == null)
859		return false;
#	Line 777 | Line 861 | public class LinkedTransferQueue<E> exte
861		Node<E> pred = traversalHead();
862		for (;;) {
863		Node<E> q = pred.next;
780	–	if (q == null || !q.isData)
781	–	return false;
864		if (q == pred) // restart
865		break;
866	+	if (q == null || !q.isData)
867	+	return false;
868		Object x = q.get();
869		if (x != null && x != q && o.equals(x) &&
870		q.compareAndSet(x, q)) {
#	Line 793 | Line 877 | public class LinkedTransferQueue<E> exte
877		}
878
879		/**
880	+	* Always returns {@code Integer.MAX_VALUE} because a
881	+	* {@code LinkedTransferQueue} is not capacity constrained.
882	+	*
883	+	* @return {@code Integer.MAX_VALUE} (as specified by
884	+	*         {@link BlockingQueue#remainingCapacity()})
885	+	*/
886	+	public int remainingCapacity() {
887	+	return Integer.MAX_VALUE;
888	+	}
889	+
890	+	/**
891		* Save the state to a stream (that is, serialize it).
892		*
893		* @serialData All of the elements (each an {@code E}) in
#	Line 842 | Line 937 | public class LinkedTransferQueue<E> exte
937
938		private static final sun.misc.Unsafe UNSAFE = getUnsafe();
939		private static final long headOffset =
940	<	objectFieldOffset("head", LinkedTransferQueue.class);
940	>	objectFieldOffset(UNSAFE, "head", LinkedTransferQueue.class);
941		private static final long tailOffset =
942	<	objectFieldOffset("tail", LinkedTransferQueue.class);
942	>	objectFieldOffset(UNSAFE, "tail", LinkedTransferQueue.class);
943		private static final long cleanMeOffset =
944	<	objectFieldOffset("cleanMe", LinkedTransferQueue.class);
944	>	objectFieldOffset(UNSAFE, "cleanMe", LinkedTransferQueue.class);
945	>
946
947	<	private static long objectFieldOffset(String field, Class<?> klazz) {
947	>	static long objectFieldOffset(sun.misc.Unsafe UNSAFE,
948	>	String field, Class<?> klazz) {
949		try {
950		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
951		} catch (NoSuchFieldException e) {

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