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

Comparing jsr166/src/jsr166y/LinkedTransferQueue.java (file contents):
Revision 1.26 by jsr166, Sat Jul 25 00:34:00 2009 UTC vs.
Revision 1.43 by jsr166, Sat Aug 1 21:24:01 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 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 element to a waiting consumer immediately, if possible.
526	+	*
527	+	* <p>More precisely, transfers the specified element immediately
528	+	* if there exists a consumer already waiting to receive it (in
529	+	* {@link #take} or timed {@link #poll(long,TimeUnit) poll}),
530	+	* otherwise returning {@code false} without enqueuing the element.
531	+	*
532	+	* @throws NullPointerException if the specified element is null
533	+	*/
534	+	public boolean tryTransfer(E e) {
535		if (e == null) throw new NullPointerException();
536	<	xfer(e, NOWAIT, 0);
468	<	return true;
536	>	return fulfill(e) != null;
537		}
538
539	+	/**
540	+	* Transfers the element to a consumer, waiting if necessary to do so.
541	+	*
542	+	* <p>More precisely, transfers the specified element immediately
543	+	* if there exists a consumer already waiting to receive it (in
544	+	* {@link #take} or timed {@link #poll(long,TimeUnit) poll}),
545	+	* else inserts the specified element at the tail of this queue
546	+	* and waits until the element is received by a consumer.
547	+	*
548	+	* @throws NullPointerException if the specified element is null
549	+	*/
550		public void transfer(E e) throws InterruptedException {
551		if (e == null) throw new NullPointerException();
552		if (xfer(e, WAIT, 0) == null) {
#	Line 476 | Line 555 | public class LinkedTransferQueue<E> exte
555		}
556		}
557
558	+	/**
559	+	* Transfers the element to a consumer if it is possible to do so
560	+	* before the timeout elapses.
561	+	*
562	+	* <p>More precisely, transfers the specified element immediately
563	+	* if there exists a consumer already waiting to receive it (in
564	+	* {@link #take} or timed {@link #poll(long,TimeUnit) poll}),
565	+	* else inserts the specified element at the tail of this queue
566	+	* and waits until the element is received by a consumer,
567	+	* returning {@code false} if the specified wait time elapses
568	+	* before the element can be transferred.
569	+	*
570	+	* @throws NullPointerException if the specified element is null
571	+	*/
572		public boolean tryTransfer(E e, long timeout, TimeUnit unit)
573		throws InterruptedException {
574		if (e == null) throw new NullPointerException();
#	Line 486 | Line 579 | public class LinkedTransferQueue<E> exte
579		throw new InterruptedException();
580		}
581
489	–	public boolean tryTransfer(E e) {
490	–	if (e == null) throw new NullPointerException();
491	–	return fulfill(e) != null;
492	–	}
493	–
582		public E take() throws InterruptedException {
583	<	Object e = xfer(null, WAIT, 0);
583	>	E e = xfer(null, WAIT, 0);
584		if (e != null)
585	<	return (E) e;
585	>	return e;
586		Thread.interrupted();
587		throw new InterruptedException();
588		}
589
590		public E poll(long timeout, TimeUnit unit) throws InterruptedException {
591	<	Object e = xfer(null, TIMEOUT, unit.toNanos(timeout));
591	>	E e = xfer(null, TIMEOUT, unit.toNanos(timeout));
592		if (e != null || !Thread.interrupted())
593	<	return (E) e;
593	>	return e;
594		throw new InterruptedException();
595		}
596
#	Line 510 | Line 598 | public class LinkedTransferQueue<E> exte
598		return fulfill(null);
599		}
600
601	+	/**
602	+	* @throws NullPointerException     {@inheritDoc}
603	+	* @throws IllegalArgumentException {@inheritDoc}
604	+	*/
605		public int drainTo(Collection<? super E> c) {
606		if (c == null)
607		throw new NullPointerException();
#	Line 524 | Line 616 | public class LinkedTransferQueue<E> exte
616		return n;
617		}
618
619	+	/**
620	+	* @throws NullPointerException     {@inheritDoc}
621	+	* @throws IllegalArgumentException {@inheritDoc}
622	+	*/
623		public int drainTo(Collection<? super E> c, int maxElements) {
624		if (c == null)
625		throw new NullPointerException();
#	Line 568 | Line 664 | public class LinkedTransferQueue<E> exte
664		}
665		}
666
667	<
667	>	/**
668	>	* Returns an iterator over the elements in this queue in proper
669	>	* sequence, from head to tail.
670	>	*
671	>	* <p>The returned iterator is a "weakly consistent" iterator that
672	>	* will never throw
673	>	* {@link ConcurrentModificationException ConcurrentModificationException},
674	>	* and guarantees to traverse elements as they existed upon
675	>	* construction of the iterator, and may (but is not guaranteed
676	>	* to) reflect any modifications subsequent to construction.
677	>	*
678	>	* @return an iterator over the elements in this queue in proper sequence
679	>	*/
680		public Iterator<E> iterator() {
681		return new Itr();
682		}
#	Line 583 | Line 691 | public class LinkedTransferQueue<E> exte
691		class Itr implements Iterator<E> {
692		Node<E> next;        // node to return next
693		Node<E> pnext;       // predecessor of next
586	–	Node<E> snext;       // successor of next
694		Node<E> curr;        // last returned node, for remove()
695		Node<E> pcurr;       // predecessor of curr, for remove()
696	<	E nextItem;        // Cache of next item, once committed to in next
696	>	E nextItem;          // Cache of next item, once committed to in next
697
698		Itr() {
699	<	findNext();
699	>	advance();
700		}
701
702		/**
703	<	* Ensures next points to next valid node, or null if none.
703	>	* Moves to next valid node and returns item to return for
704	>	* next(), or null if no such.
705		*/
706	<	void findNext() {
706	>	private E advance() {
707	>	pcurr = pnext;
708	>	curr = next;
709	>	E item = nextItem;
710	>
711		for (;;) {
712	<	Node<E> pred = pnext;
713	<	Node<E> q = next;
714	<	if (pred == null || pred == q) {
603	<	pred = traversalHead();
604	<	q = pred.next;
605	<	}
606	<	if (q == null || !q.isData) {
712	>	pnext = (next == null) ? traversalHead() : next;
713	>	next = pnext.next;
714	>	if (next == pnext) {
715		next = null;
716	<	return;
716	>	continue;  // restart
717		}
718	<	Object x = q.get();
719	<	Node<E> s = q.next;
720	<	if (x != null && q != x && q != s) {
718	>	if (next == null)
719	>	break;
720	>	Object x = next.get();
721	>	if (x != null && x != next) {
722		nextItem = (E) x;
723	<	snext = s;
615	<	pnext = pred;
616	<	next = q;
617	<	return;
723	>	break;
724		}
619	–	pnext = q;
620	–	next = s;
725		}
726	+	return item;
727		}
728
729		public boolean hasNext() {
#	Line 626 | Line 731 | public class LinkedTransferQueue<E> exte
731		}
732
733		public E next() {
734	<	if (next == null) throw new NoSuchElementException();
735	<	pcurr = pnext;
736	<	curr = next;
632	<	pnext = next;
633	<	next = snext;
634	<	E x = nextItem;
635	<	findNext();
636	<	return x;
734	>	if (next == null)
735	>	throw new NoSuchElementException();
736	>	return advance();
737		}
738
739		public void remove() {
#	Line 662 | Line 762 | public class LinkedTransferQueue<E> exte
762		}
763		}
764
765	+	/**
766	+	* Returns {@code true} if this queue contains no elements.
767	+	*
768	+	* @return {@code true} if this queue contains no elements
769	+	*/
770		public boolean isEmpty() {
771		for (;;) {
772		Node<E> h = traversalHead();
#	Line 703 | Line 808 | public class LinkedTransferQueue<E> exte
808		* @return the number of elements in this queue
809		*/
810		public int size() {
811	<	int count = 0;
812	<	Node<E> h = traversalHead();
813	<	for (Node<E> p = h.next; p != null && p.isData; p = p.next) {
814	<	Object x = p.get();
815	<	if (x != null && x != p) {
816	<	if (++count == Integer.MAX_VALUE) // saturated
811	>	for (;;) {
812	>	int count = 0;
813	>	Node<E> pred = traversalHead();
814	>	for (;;) {
815	>	Node<E> q = pred.next;
816	>	if (q == pred) // restart
817		break;
818	+	if (q == null || !q.isData)
819	+	return count;
820	+	Object x = q.get();
821	+	if (x != null && x != q) {
822	+	if (++count == Integer.MAX_VALUE) // saturated
823	+	return count;
824	+	}
825	+	pred = q;
826		}
827		}
715	–	return count;
828		}
829
830		public int getWaitingConsumerCount() {
831	<	int count = 0;
832	<	Node<E> h = traversalHead();
833	<	for (Node<E> p = h.next; p != null && !p.isData; p = p.next) {
834	<	if (p.get() == null) {
835	<	if (++count == Integer.MAX_VALUE)
831	>	// converse of size -- count valid non-data nodes
832	>	for (;;) {
833	>	int count = 0;
834	>	Node<E> pred = traversalHead();
835	>	for (;;) {
836	>	Node<E> q = pred.next;
837	>	if (q == pred) // restart
838		break;
839	+	if (q == null || q.isData)
840	+	return count;
841	+	Object x = q.get();
842	+	if (x == null) {
843	+	if (++count == Integer.MAX_VALUE) // saturated
844	+	return count;
845	+	}
846	+	pred = q;
847		}
848		}
727	–	return count;
728	–	}
729	–
730	–	public int remainingCapacity() {
731	–	return Integer.MAX_VALUE;
849		}
850
851	+	/**
852	+	* Removes a single instance of the specified element from this queue,
853	+	* if it is present.  More formally, removes an element {@code e} such
854	+	* that {@code o.equals(e)}, if this queue contains one or more such
855	+	* elements.
856	+	* Returns {@code true} if this queue contained the specified element
857	+	* (or equivalently, if this queue changed as a result of the call).
858	+	*
859	+	* @param o element to be removed from this queue, if present
860	+	* @return {@code true} if this queue changed as a result of the call
861	+	*/
862		public boolean remove(Object o) {
863		if (o == null)
864		return false;
#	Line 738 | Line 866 | public class LinkedTransferQueue<E> exte
866		Node<E> pred = traversalHead();
867		for (;;) {
868		Node<E> q = pred.next;
741	–	if (q == null || !q.isData)
742	–	return false;
869		if (q == pred) // restart
870		break;
871	+	if (q == null || !q.isData)
872	+	return false;
873		Object x = q.get();
874		if (x != null && x != q && o.equals(x) &&
875		q.compareAndSet(x, q)) {
#	Line 754 | Line 882 | public class LinkedTransferQueue<E> exte
882		}
883
884		/**
885	+	* Always returns {@code Integer.MAX_VALUE} because a
886	+	* {@code LinkedTransferQueue} is not capacity constrained.
887	+	*
888	+	* @return {@code Integer.MAX_VALUE} (as specified by
889	+	*         {@link BlockingQueue#remainingCapacity()})
890	+	*/
891	+	public int remainingCapacity() {
892	+	return Integer.MAX_VALUE;
893	+	}
894	+
895	+	/**
896		* Save the state to a stream (that is, serialize it).
897		*
898		* @serialData All of the elements (each an {@code E}) in
#	Line 799 | Line 938 | public class LinkedTransferQueue<E> exte
938		new PaddedAtomicReference<Node<E>>(null));
939		}
940
941	<	// Unsafe mechanics for jsr166y 3rd party package.
941	>	// Unsafe mechanics
942	>
943	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
944	>	private static final long headOffset =
945	>	objectFieldOffset(UNSAFE, "head", LinkedTransferQueue.class);
946	>	private static final long tailOffset =
947	>	objectFieldOffset(UNSAFE, "tail", LinkedTransferQueue.class);
948	>	private static final long cleanMeOffset =
949	>	objectFieldOffset(UNSAFE, "cleanMe", LinkedTransferQueue.class);
950	>
951	>
952	>	static long objectFieldOffset(sun.misc.Unsafe UNSAFE,
953	>	String field, Class<?> klazz) {
954	>	try {
955	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
956	>	} catch (NoSuchFieldException e) {
957	>	// Convert Exception to corresponding Error
958	>	NoSuchFieldError error = new NoSuchFieldError(field);
959	>	error.initCause(e);
960	>	throw error;
961	>	}
962	>	}
963	>
964	>	/**
965	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
966	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
967	>	* into a jdk.
968	>	*
969	>	* @return a sun.misc.Unsafe
970	>	*/
971		private static sun.misc.Unsafe getUnsafe() {
972		try {
973		return sun.misc.Unsafe.getUnsafe();
974		} catch (SecurityException se) {
975		try {
976		return java.security.AccessController.doPrivileged
977	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
977	>	(new java.security
978	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
979		public sun.misc.Unsafe run() throws Exception {
980	<	return getUnsafeByReflection();
980	>	java.lang.reflect.Field f = sun.misc
981	>	.Unsafe.class.getDeclaredField("theUnsafe");
982	>	f.setAccessible(true);
983	>	return (sun.misc.Unsafe) f.get(null);
984		}});
985		} catch (java.security.PrivilegedActionException e) {
986		throw new RuntimeException("Could not initialize intrinsics",
#	Line 816 | Line 988 | public class LinkedTransferQueue<E> exte
988		}
989		}
990		}
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	–	static final long headOffset =
841	–	fieldOffset("head", LinkedTransferQueue.class);
842	–	static final long tailOffset =
843	–	fieldOffset("tail", LinkedTransferQueue.class);
844	–	static final long cleanMeOffset =
845	–	fieldOffset("cleanMe", LinkedTransferQueue.class);
846	–
991		}

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