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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 1.35 by jsr166, Thu Jul 30 22:45:39 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 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(Object,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 InterruptedException {@inheritDoc}
543	+	* @throws NullPointerException if the specified element is null
544	+	*/
545		public void transfer(E e) throws InterruptedException {
546		if (e == null) throw new NullPointerException();
547		if (xfer(e, WAIT, 0) == null) {
#	Line 476 | Line 550 | public class LinkedTransferQueue<E> exte
550		}
551		}
552
553	+	/**
554	+	* Inserts the specified element at the tail of this queue,
555	+	* waiting up to the specified wait time for the element to be
556	+	* received by a consumer invoking {@code take} or {@code poll}.
557	+	*
558	+	* @throws InterruptedException {@inheritDoc}
559	+	* @throws NullPointerException if the specified element is null
560	+	*/
561		public boolean tryTransfer(E e, long timeout, TimeUnit unit)
562		throws InterruptedException {
563		if (e == null) throw new NullPointerException();
#	Line 486 | Line 568 | public class LinkedTransferQueue<E> exte
568		throw new InterruptedException();
569		}
570
489	–	public boolean tryTransfer(E e) {
490	–	if (e == null) throw new NullPointerException();
491	–	return fulfill(e) != null;
492	–	}
493	–
571		public E take() throws InterruptedException {
572	<	Object e = xfer(null, WAIT, 0);
572	>	E e = xfer(null, WAIT, 0);
573		if (e != null)
574	<	return (E) e;
574	>	return e;
575		Thread.interrupted();
576		throw new InterruptedException();
577		}
578
579	+	/**
580	+	* @throws InterruptedException {@inheritDoc}
581	+	*/
582		public E poll(long timeout, TimeUnit unit) throws InterruptedException {
583	<	Object e = xfer(null, TIMEOUT, unit.toNanos(timeout));
583	>	E e = xfer(null, TIMEOUT, unit.toNanos(timeout));
584		if (e != null || !Thread.interrupted())
585	<	return (E) e;
585	>	return e;
586		throw new InterruptedException();
587		}
588
#	Line 510 | Line 590 | public class LinkedTransferQueue<E> exte
590		return fulfill(null);
591		}
592
593	+	/**
594	+	* @throws NullPointerException     {@inheritDoc}
595	+	* @throws IllegalArgumentException {@inheritDoc}
596	+	*/
597		public int drainTo(Collection<? super E> c) {
598		if (c == null)
599		throw new NullPointerException();
#	Line 524 | Line 608 | public class LinkedTransferQueue<E> exte
608		return n;
609		}
610
611	+	/**
612	+	* @throws NullPointerException     {@inheritDoc}
613	+	* @throws IllegalArgumentException {@inheritDoc}
614	+	*/
615		public int drainTo(Collection<? super E> c, int maxElements) {
616		if (c == null)
617		throw new NullPointerException();
#	Line 568 | Line 656 | public class LinkedTransferQueue<E> exte
656		}
657		}
658
659	<
659	>	/**
660	>	* Returns an iterator over the elements in this queue in proper
661	>	* sequence, from head to tail.
662	>	*
663	>	* <p>The returned iterator is a "weakly consistent" iterator that
664	>	* will never throw
665	>	* {@link ConcurrentModificationException ConcurrentModificationException},
666	>	* and guarantees to traverse elements as they existed upon
667	>	* construction of the iterator, and may (but is not guaranteed
668	>	* to) reflect any modifications subsequent to construction.
669	>	*
670	>	* @return an iterator over the elements in this queue in proper sequence
671	>	*/
672		public Iterator<E> iterator() {
673		return new Itr();
674		}
#	Line 583 | Line 683 | public class LinkedTransferQueue<E> exte
683		class Itr implements Iterator<E> {
684		Node<E> next;        // node to return next
685		Node<E> pnext;       // predecessor of next
586	–	Node<E> snext;       // successor of next
686		Node<E> curr;        // last returned node, for remove()
687		Node<E> pcurr;       // predecessor of curr, for remove()
688	<	E nextItem;        // Cache of next item, once committed to in next
688	>	E nextItem;          // Cache of next item, once committed to in next
689
690		Itr() {
691	<	findNext();
691	>	advance();
692		}
693
694		/**
695	<	* Ensures next points to next valid node, or null if none.
695	>	* Moves to next valid node and returns item to return for
696	>	* next(), or null if no such.
697		*/
698	<	void findNext() {
698	>	private E advance() {
699	>	pcurr = pnext;
700	>	curr = next;
701	>	E item = nextItem;
702	>
703		for (;;) {
704	<	Node<E> pred = pnext;
705	<	Node<E> q = next;
706	<	if (pred == null || pred == q) {
603	<	pred = traversalHead();
604	<	q = pred.next;
605	<	}
606	<	if (q == null || !q.isData) {
704	>	pnext = (next == null) ? traversalHead() : next;
705	>	next = pnext.next;
706	>	if (next == pnext) {
707		next = null;
708	<	return;
708	>	continue;  // restart
709		}
710	<	Object x = q.get();
711	<	Node<E> s = q.next;
712	<	if (x != null && q != x && q != s) {
710	>	if (next == null)
711	>	break;
712	>	Object x = next.get();
713	>	if (x != null && x != next) {
714		nextItem = (E) x;
715	<	snext = s;
615	<	pnext = pred;
616	<	next = q;
617	<	return;
715	>	break;
716		}
619	–	pnext = q;
620	–	next = s;
717		}
718	+	return item;
719		}
720
721		public boolean hasNext() {
#	Line 626 | Line 723 | public class LinkedTransferQueue<E> exte
723		}
724
725		public E next() {
726	<	if (next == null) throw new NoSuchElementException();
727	<	pcurr = pnext;
728	<	curr = next;
632	<	pnext = next;
633	<	next = snext;
634	<	E x = nextItem;
635	<	findNext();
636	<	return x;
726	>	if (next == null)
727	>	throw new NoSuchElementException();
728	>	return advance();
729		}
730
731		public void remove() {
#	Line 703 | Line 795 | public class LinkedTransferQueue<E> exte
795		* @return the number of elements in this queue
796		*/
797		public int size() {
798	<	int count = 0;
799	<	Node<E> h = traversalHead();
800	<	for (Node<E> p = h.next; p != null && p.isData; p = p.next) {
801	<	Object x = p.get();
802	<	if (x != null && x != p) {
803	<	if (++count == Integer.MAX_VALUE) // saturated
798	>	for (;;) {
799	>	int count = 0;
800	>	Node<E> pred = traversalHead();
801	>	for (;;) {
802	>	Node<E> q = pred.next;
803	>	if (q == pred) // restart
804		break;
805	+	if (q == null || !q.isData)
806	+	return count;
807	+	Object x = q.get();
808	+	if (x != null && x != q) {
809	+	if (++count == Integer.MAX_VALUE) // saturated
810	+	return count;
811	+	}
812	+	pred = q;
813		}
814		}
715	–	return count;
815		}
816
817		public int getWaitingConsumerCount() {
818	<	int count = 0;
819	<	Node<E> h = traversalHead();
820	<	for (Node<E> p = h.next; p != null && !p.isData; p = p.next) {
821	<	if (p.get() == null) {
822	<	if (++count == Integer.MAX_VALUE)
818	>	// converse of size -- count valid non-data nodes
819	>	for (;;) {
820	>	int count = 0;
821	>	Node<E> pred = traversalHead();
822	>	for (;;) {
823	>	Node<E> q = pred.next;
824	>	if (q == pred) // restart
825		break;
826	+	if (q == null || q.isData)
827	+	return count;
828	+	Object x = q.get();
829	+	if (x == null) {
830	+	if (++count == Integer.MAX_VALUE) // saturated
831	+	return count;
832	+	}
833	+	pred = q;
834		}
835		}
727	–	return count;
728	–	}
729	–
730	–	public int remainingCapacity() {
731	–	return Integer.MAX_VALUE;
836		}
837
838		public boolean remove(Object o) {
#	Line 738 | Line 842 | public class LinkedTransferQueue<E> exte
842		Node<E> pred = traversalHead();
843		for (;;) {
844		Node<E> q = pred.next;
741	–	if (q == null || !q.isData)
742	–	return false;
845		if (q == pred) // restart
846		break;
847	+	if (q == null || !q.isData)
848	+	return false;
849		Object x = q.get();
850		if (x != null && x != q && o.equals(x) &&
851		q.compareAndSet(x, q)) {
#	Line 754 | Line 858 | public class LinkedTransferQueue<E> exte
858		}
859
860		/**
861	+	* Always returns {@code Integer.MAX_VALUE} because a
862	+	* {@code LinkedTransferQueue} is not capacity constrained.
863	+	*
864	+	* @return {@code Integer.MAX_VALUE} (as specified by
865	+	*         {@link BlockingQueue#remainingCapacity()})
866	+	*/
867	+	public int remainingCapacity() {
868	+	return Integer.MAX_VALUE;
869	+	}
870	+
871	+	/**
872		* Save the state to a stream (that is, serialize it).
873		*
874		* @serialData All of the elements (each an {@code E}) in
#	Line 799 | Line 914 | public class LinkedTransferQueue<E> exte
914		new PaddedAtomicReference<Node<E>>(null));
915		}
916
917	<	// Unsafe mechanics for jsr166y 3rd party package.
917	>	// Unsafe mechanics
918	>
919	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
920	>	private static final long headOffset =
921	>	objectFieldOffset(UNSAFE, "head", LinkedTransferQueue.class);
922	>	private static final long tailOffset =
923	>	objectFieldOffset(UNSAFE, "tail", LinkedTransferQueue.class);
924	>	private static final long cleanMeOffset =
925	>	objectFieldOffset(UNSAFE, "cleanMe", LinkedTransferQueue.class);
926	>
927	>
928	>	static long objectFieldOffset(sun.misc.Unsafe UNSAFE,
929	>	String field, Class<?> klazz) {
930	>	try {
931	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
932	>	} catch (NoSuchFieldException e) {
933	>	// Convert Exception to corresponding Error
934	>	NoSuchFieldError error = new NoSuchFieldError(field);
935	>	error.initCause(e);
936	>	throw error;
937	>	}
938	>	}
939	>
940	>	/**
941	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
942	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
943	>	* into a jdk.
944	>	*
945	>	* @return a sun.misc.Unsafe
946	>	*/
947		private static sun.misc.Unsafe getUnsafe() {
948		try {
949		return sun.misc.Unsafe.getUnsafe();
950		} catch (SecurityException se) {
951		try {
952		return java.security.AccessController.doPrivileged
953	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
953	>	(new java.security
954	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
955		public sun.misc.Unsafe run() throws Exception {
956	<	return getUnsafeByReflection();
956	>	java.lang.reflect.Field f = sun.misc
957	>	.Unsafe.class.getDeclaredField("theUnsafe");
958	>	f.setAccessible(true);
959	>	return (sun.misc.Unsafe) f.get(null);
960		}});
961		} catch (java.security.PrivilegedActionException e) {
962		throw new RuntimeException("Could not initialize intrinsics",
#	Line 816 | Line 964 | public class LinkedTransferQueue<E> exte
964		}
965		}
966		}
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	–
967		}

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