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

Comparing jsr166/src/jsr166y/LinkedTransferQueue.java (file contents):
Revision 1.12 by dl, Mon Jan 12 17:16:18 2009 UTC vs.
Revision 1.34 by jsr166, Thu Jul 30 17:30:26 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	+
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import java.util.*;
13	<	import java.io.*;
14	<	import sun.misc.Unsafe;
15	<	import java.lang.reflect.*;
10	>
11	>	import java.util.AbstractQueue;
12	>	import java.util.Collection;
13	>	import java.util.Iterator;
14	>	import java.util.NoSuchElementException;
15	>	import java.util.concurrent.locks.LockSupport;
16	>	import java.util.concurrent.atomic.AtomicReference;
17
18		/**
19		* An unbounded {@linkplain TransferQueue} based on linked nodes.
#	Line 44 | Line 46 | import java.lang.reflect.*;
46		* @since 1.7
47		* @author Doug Lea
48		* @param <E> the type of elements held in this collection
47	–	*
49		*/
50		public class LinkedTransferQueue<E> extends AbstractQueue<E>
51		implements TransferQueue<E>, java.io.Serializable {
#	Line 81 | Line 82 | public class LinkedTransferQueue<E> exte
82		* seems not to vary with number of CPUs (beyond 2) so is just
83		* a constant.
84		*/
85	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
85	>	static final int maxTimedSpins = (NCPUS < 2) ? 0 : 32;
86
87		/**
88		* The number of times to spin before blocking in untimed waits.
#	Line 103 | Line 104 | public class LinkedTransferQueue<E> exte
104		* garbage retention. Similarly, setting the next field to this is
105		* used as sentinel that node is off list.
106		*/
107	<	static final class QNode extends AtomicReference<Object> {
108	<	volatile QNode next;
107	>	static final class Node<E> extends AtomicReference<Object> {
108	>	volatile Node<E> next;
109		volatile Thread waiter;       // to control park/unpark
110		final boolean isData;
111	<	QNode(Object item, boolean isData) {
111	>
112	>	Node(E item, boolean isData) {
113		super(item);
114		this.isData = isData;
115		}
116
117	<	static final AtomicReferenceFieldUpdater<QNode, QNode>
118	<	nextUpdater = AtomicReferenceFieldUpdater.newUpdater
119	<	(QNode.class, QNode.class, "next");
117	>	// Unsafe mechanics
118	>
119	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
120	>	private static final long nextOffset =
121	>	objectFieldOffset(UNSAFE, "next", Node.class);
122
123	<	boolean casNext(QNode cmp, QNode val) {
124	<	return nextUpdater.compareAndSet(this, cmp, val);
123	>	final boolean casNext(Node<E> cmp, Node<E> val) {
124	>	return UNSAFE.compareAndSwapObject(this, nextOffset, cmp, val);
125		}
126	+
127	+	final void clearNext() {
128	+	UNSAFE.putOrderedObject(this, nextOffset, this);
129	+	}
130	+
131	+	/**
132	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
133	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
134	+	* into a jdk.
135	+	*
136	+	* @return a sun.misc.Unsafe
137	+	*/
138	+	private static sun.misc.Unsafe getUnsafe() {
139	+	try {
140	+	return sun.misc.Unsafe.getUnsafe();
141	+	} catch (SecurityException se) {
142	+	try {
143	+	return java.security.AccessController.doPrivileged
144	+	(new java.security
145	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
146	+	public sun.misc.Unsafe run() throws Exception {
147	+	java.lang.reflect.Field f = sun.misc
148	+	.Unsafe.class.getDeclaredField("theUnsafe");
149	+	f.setAccessible(true);
150	+	return (sun.misc.Unsafe) f.get(null);
151	+	}});
152	+	} catch (java.security.PrivilegedActionException e) {
153	+	throw new RuntimeException("Could not initialize intrinsics",
154	+	e.getCause());
155	+	}
156	+	}
157	+	}
158	+
159	+	private static final long serialVersionUID = -3375979862319811754L;
160		}
161
162		/**
#	Line 130 | Line 168 | public class LinkedTransferQueue<E> exte
168		// enough padding for 64bytes with 4byte refs
169		Object p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, pa, pb, pc, pd, pe;
170		PaddedAtomicReference(T r) { super(r); }
171	+	private static final long serialVersionUID = 8170090609809740854L;
172		}
173
174
175		/** head of the queue */
176	<	private transient final PaddedAtomicReference<QNode> head;
176	>	private transient final PaddedAtomicReference<Node<E>> head;
177	>
178		/** tail of the queue */
179	<	private transient final PaddedAtomicReference<QNode> tail;
179	>	private transient final PaddedAtomicReference<Node<E>> tail;
180
181		/**
182		* Reference to a cancelled node that might not yet have been
183		* unlinked from queue because it was the last inserted node
184		* when it cancelled.
185		*/
186	<	private transient final PaddedAtomicReference<QNode> cleanMe;
186	>	private transient final PaddedAtomicReference<Node<E>> cleanMe;
187
188		/**
189		* Tries to cas nh as new head; if successful, unlink
190		* old head's next node to avoid garbage retention.
191		*/
192	<	private boolean advanceHead(QNode h, QNode nh) {
192	>	private boolean advanceHead(Node<E> h, Node<E> nh) {
193		if (h == head.get() && head.compareAndSet(h, nh)) {
194	<	h.next = h; // forget old next
194	>	h.clearNext(); // forget old next
195		return true;
196		}
197		return false;
#	Line 161 | Line 201 | public class LinkedTransferQueue<E> exte
201		* Puts or takes an item. Used for most queue operations (except
202		* poll() and tryTransfer()). See the similar code in
203		* SynchronousQueue for detailed explanation.
204	+	*
205		* @param e the item or if null, signifies that this is a take
206		* @param mode the wait mode: NOWAIT, TIMEOUT, WAIT
207		* @param nanos timeout in nanosecs, used only if mode is TIMEOUT
208		* @return an item, or null on failure
209		*/
210	<	private Object xfer(Object e, int mode, long nanos) {
210	>	private E xfer(E e, int mode, long nanos) {
211		boolean isData = (e != null);
212	<	QNode s = null;
213	<	final PaddedAtomicReference<QNode> head = this.head;
214	<	final PaddedAtomicReference<QNode> tail = this.tail;
212	>	Node<E> s = null;
213	>	final PaddedAtomicReference<Node<E>> head = this.head;
214	>	final PaddedAtomicReference<Node<E>> tail = this.tail;
215
216		for (;;) {
217	<	QNode t = tail.get();
218	<	QNode h = head.get();
217	>	Node<E> t = tail.get();
218	>	Node<E> h = head.get();
219
220		if (t != null && (t == h || t.isData == isData)) {
221		if (s == null)
222	<	s = new QNode(e, isData);
223	<	QNode last = t.next;
222	>	s = new Node<E>(e, isData);
223	>	Node<E> last = t.next;
224		if (last != null) {
225		if (t == tail.get())
226		tail.compareAndSet(t, last);
#	Line 191 | Line 232 | public class LinkedTransferQueue<E> exte
232		}
233
234		else if (h != null) {
235	<	QNode first = h.next;
235	>	Node<E> first = h.next;
236		if (t == tail.get() && first != null &&
237		advanceHead(h, first)) {
238		Object x = first.get();
239		if (x != first && first.compareAndSet(x, e)) {
240		LockSupport.unpark(first.waiter);
241	<	return isData? e : x;
241	>	return isData ? e : (E) x;
242		}
243		}
244		}
#	Line 207 | Line 248 | public class LinkedTransferQueue<E> exte
248
249		/**
250		* Version of xfer for poll() and tryTransfer, which
251	<	* simplifies control paths both here and in xfer
251	>	* simplifies control paths both here and in xfer.
252		*/
253	<	private Object fulfill(Object e) {
253	>	private E fulfill(E e) {
254		boolean isData = (e != null);
255	<	final PaddedAtomicReference<QNode> head = this.head;
256	<	final PaddedAtomicReference<QNode> tail = this.tail;
255	>	final PaddedAtomicReference<Node<E>> head = this.head;
256	>	final PaddedAtomicReference<Node<E>> tail = this.tail;
257
258		for (;;) {
259	<	QNode t = tail.get();
260	<	QNode h = head.get();
259	>	Node<E> t = tail.get();
260	>	Node<E> h = head.get();
261
262		if (t != null && (t == h || t.isData == isData)) {
263	<	QNode last = t.next;
263	>	Node<E> last = t.next;
264		if (t == tail.get()) {
265		if (last != null)
266		tail.compareAndSet(t, last);
#	Line 228 | Line 269 | public class LinkedTransferQueue<E> exte
269		}
270		}
271		else if (h != null) {
272	<	QNode first = h.next;
272	>	Node<E> first = h.next;
273		if (t == tail.get() &&
274		first != null &&
275		advanceHead(h, first)) {
276		Object x = first.get();
277		if (x != first && first.compareAndSet(x, e)) {
278		LockSupport.unpark(first.waiter);
279	<	return isData? e : x;
279	>	return isData ? e : (E) x;
280		}
281		}
282		}
#	Line 253 | Line 294 | public class LinkedTransferQueue<E> exte
294		* @param nanos timeout value
295		* @return matched item, or s if cancelled
296		*/
297	<	private Object awaitFulfill(QNode pred, QNode s, Object e,
298	<	int mode, long nanos) {
297	>	private E awaitFulfill(Node<E> pred, Node<E> s, E e,
298	>	int mode, long nanos) {
299		if (mode == NOWAIT)
300		return null;
301
302	<	long lastTime = (mode == TIMEOUT)? System.nanoTime() : 0;
302	>	long lastTime = (mode == TIMEOUT) ? System.nanoTime() : 0;
303		Thread w = Thread.currentThread();
304		int spins = -1; // set to desired spin count below
305		for (;;) {
#	Line 267 | Line 308 | public class LinkedTransferQueue<E> exte
308		Object x = s.get();
309		if (x != e) {                 // Node was matched or cancelled
310		advanceHead(pred, s);     // unlink if head
311	<	if (x == s) {              // was cancelled
311	>	if (x == s) {             // was cancelled
312		clean(pred, s);
313		return null;
314		}
315		else if (x != null) {
316		s.set(s);             // avoid garbage retention
317	<	return x;
317	>	return (E) x;
318		}
319		else
320		return e;
#	Line 288 | Line 329 | public class LinkedTransferQueue<E> exte
329		}
330		}
331		if (spins < 0) {
332	<	QNode h = head.get(); // only spin if at head
332	>	Node<E> h = head.get(); // only spin if at head
333		spins = ((h != null && h.next == s) ?
334	<	(mode == TIMEOUT?
334	>	((mode == TIMEOUT) ?
335		maxTimedSpins : maxUntimedSpins) : 0);
336		}
337		if (spins > 0)
#	Line 311 | Line 352 | public class LinkedTransferQueue<E> exte
352		}
353
354		/**
355	<	* Returns validated tail for use in cleaning methods
355	>	* Returns validated tail for use in cleaning methods.
356		*/
357	<	private QNode getValidatedTail() {
357	>	private Node<E> getValidatedTail() {
358		for (;;) {
359	<	QNode h = head.get();
360	<	QNode first = h.next;
359	>	Node<E> h = head.get();
360	>	Node<E> first = h.next;
361		if (first != null && first.next == first) { // help advance
362		advanceHead(h, first);
363		continue;
364		}
365	<	QNode t = tail.get();
366	<	QNode last = t.next;
365	>	Node<E> t = tail.get();
366	>	Node<E> last = t.next;
367		if (t == tail.get()) {
368		if (last != null)
369		tail.compareAndSet(t, last); // help advance
#	Line 334 | Line 375 | public class LinkedTransferQueue<E> exte
375
376		/**
377		* Gets rid of cancelled node s with original predecessor pred.
378	+	*
379		* @param pred predecessor of cancelled node
380		* @param s the cancelled node
381		*/
382	<	private void clean(QNode pred, QNode s) {
382	>	private void clean(Node<E> pred, Node<E> s) {
383		Thread w = s.waiter;
384		if (w != null) {             // Wake up thread
385		s.waiter = null;
386		if (w != Thread.currentThread())
387		LockSupport.unpark(w);
388		}
389	+
390	+	if (pred == null)
391	+	return;
392	+
393		/*
394		* At any given time, exactly one node on list cannot be
395		* deleted -- the last inserted node. To accommodate this, if
#	Line 353 | Line 399 | public class LinkedTransferQueue<E> exte
399		* processed, so this always terminates.
400		*/
401		while (pred.next == s) {
402	<	QNode oldpred = reclean();  // First, help get rid of cleanMe
403	<	QNode t = getValidatedTail();
402	>	Node<E> oldpred = reclean();  // First, help get rid of cleanMe
403	>	Node<E> t = getValidatedTail();
404		if (s != t) {               // If not tail, try to unsplice
405	<	QNode sn = s.next;      // s.next == s means s already off list
405	>	Node<E> sn = s.next;      // s.next == s means s already off list
406		if (sn == s || pred.casNext(s, sn))
407		break;
408		}
#	Line 369 | Line 415 | public class LinkedTransferQueue<E> exte
415		/**
416		* Tries to unsplice the cancelled node held in cleanMe that was
417		* previously uncleanable because it was at tail.
418	+	*
419		* @return current cleanMe node (or null)
420		*/
421	<	private QNode reclean() {
421	>	private Node<E> reclean() {
422		/*
423		* cleanMe is, or at one time was, predecessor of cancelled
424		* node s that was the tail so could not be unspliced.  If s
#	Line 383 | Line 430 | public class LinkedTransferQueue<E> exte
430		* This can loop only due to contention on casNext or
431		* clearing cleanMe.
432		*/
433	<	QNode pred;
433	>	Node<E> pred;
434		while ((pred = cleanMe.get()) != null) {
435	<	QNode t = getValidatedTail();
436	<	QNode s = pred.next;
435	>	Node<E> t = getValidatedTail();
436	>	Node<E> s = pred.next;
437		if (s != t) {
438	<	QNode sn;
438	>	Node<E> sn;
439		if (s == null || s == pred || s.get() != s ||
440		(sn = s.next) == s || pred.casNext(s, sn))
441		cleanMe.compareAndSet(pred, null);
#	Line 403 | Line 450 | public class LinkedTransferQueue<E> exte
450		* Creates an initially empty {@code LinkedTransferQueue}.
451		*/
452		public LinkedTransferQueue() {
453	<	QNode dummy = new QNode(null, false);
454	<	head = new PaddedAtomicReference<QNode>(dummy);
455	<	tail = new PaddedAtomicReference<QNode>(dummy);
456	<	cleanMe = new PaddedAtomicReference<QNode>(null);
453	>	Node<E> dummy = new Node<E>(null, false);
454	>	head = new PaddedAtomicReference<Node<E>>(dummy);
455	>	tail = new PaddedAtomicReference<Node<E>>(dummy);
456	>	cleanMe = new PaddedAtomicReference<Node<E>>(null);
457		}
458
459		/**
460		* Creates a {@code LinkedTransferQueue}
461		* initially containing the elements of the given collection,
462		* added in traversal order of the collection's iterator.
463	+	*
464		* @param c the collection of elements to initially contain
465		* @throws NullPointerException if the specified collection or any
466		*         of its elements are null
#	Line 422 | Line 470 | public class LinkedTransferQueue<E> exte
470		addAll(c);
471		}
472
473	+	/**
474	+	* @throws InterruptedException {@inheritDoc}
475	+	* @throws NullPointerException {@inheritDoc}
476	+	*/
477		public void put(E e) throws InterruptedException {
478		if (e == null) throw new NullPointerException();
479		if (Thread.interrupted()) throw new InterruptedException();
480		xfer(e, NOWAIT, 0);
481		}
482
483	+	/**
484	+	* @throws InterruptedException {@inheritDoc}
485	+	* @throws NullPointerException {@inheritDoc}
486	+	*/
487		public boolean offer(E e, long timeout, TimeUnit unit)
488		throws InterruptedException {
489		if (e == null) throw new NullPointerException();
#	Line 436 | Line 492 | public class LinkedTransferQueue<E> exte
492		return true;
493		}
494
495	+	/**
496	+	* @throws NullPointerException {@inheritDoc}
497	+	*/
498		public boolean offer(E e) {
499		if (e == null) throw new NullPointerException();
500		xfer(e, NOWAIT, 0);
501		return true;
502		}
503
504	+	/**
505	+	* @throws NullPointerException {@inheritDoc}
506	+	*/
507	+	public boolean add(E e) {
508	+	if (e == null) throw new NullPointerException();
509	+	xfer(e, NOWAIT, 0);
510	+	return true;
511	+	}
512	+
513	+	/**
514	+	* @throws InterruptedException {@inheritDoc}
515	+	* @throws NullPointerException {@inheritDoc}
516	+	*/
517		public void transfer(E e) throws InterruptedException {
518		if (e == null) throw new NullPointerException();
519		if (xfer(e, WAIT, 0) == null) {
#	Line 450 | Line 522 | public class LinkedTransferQueue<E> exte
522		}
523		}
524
525	+	/**
526	+	* @throws InterruptedException {@inheritDoc}
527	+	* @throws NullPointerException {@inheritDoc}
528	+	*/
529		public boolean tryTransfer(E e, long timeout, TimeUnit unit)
530		throws InterruptedException {
531		if (e == null) throw new NullPointerException();
#	Line 460 | Line 536 | public class LinkedTransferQueue<E> exte
536		throw new InterruptedException();
537		}
538
539	+	/**
540	+	* @throws NullPointerException {@inheritDoc}
541	+	*/
542		public boolean tryTransfer(E e) {
543		if (e == null) throw new NullPointerException();
544		return fulfill(e) != null;
545		}
546
547	+	/**
548	+	* @throws InterruptedException {@inheritDoc}
549	+	*/
550		public E take() throws InterruptedException {
551	<	Object e = xfer(null, WAIT, 0);
551	>	E e = xfer(null, WAIT, 0);
552		if (e != null)
553	<	return (E)e;
553	>	return e;
554		Thread.interrupted();
555		throw new InterruptedException();
556		}
557
558	+	/**
559	+	* @throws InterruptedException {@inheritDoc}
560	+	*/
561		public E poll(long timeout, TimeUnit unit) throws InterruptedException {
562	<	Object e = xfer(null, TIMEOUT, unit.toNanos(timeout));
562	>	E e = xfer(null, TIMEOUT, unit.toNanos(timeout));
563		if (e != null || !Thread.interrupted())
564	<	return (E)e;
564	>	return e;
565		throw new InterruptedException();
566		}
567
568		public E poll() {
569	<	return (E)fulfill(null);
569	>	return fulfill(null);
570		}
571
572	+	/**
573	+	* @throws NullPointerException     {@inheritDoc}
574	+	* @throws IllegalArgumentException {@inheritDoc}
575	+	*/
576		public int drainTo(Collection<? super E> c) {
577		if (c == null)
578		throw new NullPointerException();
#	Line 498 | Line 587 | public class LinkedTransferQueue<E> exte
587		return n;
588		}
589
590	+	/**
591	+	* @throws NullPointerException     {@inheritDoc}
592	+	* @throws IllegalArgumentException {@inheritDoc}
593	+	*/
594		public int drainTo(Collection<? super E> c, int maxElements) {
595		if (c == null)
596		throw new NullPointerException();
#	Line 515 | Line 608 | public class LinkedTransferQueue<E> exte
608		// Traversal-based methods
609
610		/**
611	<	* Return head after performing any outstanding helping steps
611	>	* Returns head after performing any outstanding helping steps.
612		*/
613	<	private QNode traversalHead() {
613	>	private Node<E> traversalHead() {
614		for (;;) {
615	<	QNode t = tail.get();
616	<	QNode h = head.get();
615	>	Node<E> t = tail.get();
616	>	Node<E> h = head.get();
617		if (h != null && t != null) {
618	<	QNode last = t.next;
619	<	QNode first = h.next;
618	>	Node<E> last = t.next;
619	>	Node<E> first = h.next;
620		if (t == tail.get()) {
621		if (last != null)
622		tail.compareAndSet(t, last);
#	Line 538 | Line 631 | public class LinkedTransferQueue<E> exte
631		return h;
632		}
633		}
634	+	reclean();
635		}
636		}
637
544	–
638		public Iterator<E> iterator() {
639		return new Itr();
640		}
#	Line 554 | Line 647 | public class LinkedTransferQueue<E> exte
647		* if subsequently removed.
648		*/
649		class Itr implements Iterator<E> {
650	<	QNode nextNode;    // Next node to return next
651	<	QNode currentNode; // last returned node, for remove()
652	<	QNode prevNode;    // predecessor of last returned node
653	<	E nextItem;        // Cache of next item, once commited to in next
650	>	Node<E> next;        // node to return next
651	>	Node<E> pnext;       // predecessor of next
652	>	Node<E> curr;        // last returned node, for remove()
653	>	Node<E> pcurr;       // predecessor of curr, for remove()
654	>	E nextItem;          // Cache of next item, once committed to in next
655
656		Itr() {
563	–	nextNode = traversalHead();
657		advance();
658		}
659
660	<	E advance() {
661	<	prevNode = currentNode;
662	<	currentNode = nextNode;
663	<	E x = nextItem;
660	>	/**
661	>	* Moves to next valid node and returns item to return for
662	>	* next(), or null if no such.
663	>	*/
664	>	private E advance() {
665	>	pcurr = pnext;
666	>	curr = next;
667	>	E item = nextItem;
668
572	–	QNode p = nextNode.next;
669		for (;;) {
670	<	if (p == null || !p.isData) {
671	<	nextNode = null;
672	<	nextItem = null;
673	<	return x;
674	<	}
675	<	Object item = p.get();
676	<	if (item != p && item != null) {
677	<	nextNode = p;
678	<	nextItem = (E)item;
679	<	return x;
670	>	pnext = (next == null) ? traversalHead() : next;
671	>	next = pnext.next;
672	>	if (next == pnext) {
673	>	next = null;
674	>	continue;  // restart
675	>	}
676	>	if (next == null)
677	>	break;
678	>	Object x = next.get();
679	>	if (x != null && x != next) {
680	>	nextItem = (E) x;
681	>	break;
682		}
585	–	prevNode = p;
586	–	p = p.next;
683		}
684	+	return item;
685		}
686
687		public boolean hasNext() {
688	<	return nextNode != null;
688	>	return next != null;
689		}
690
691		public E next() {
692	<	if (nextNode == null) throw new NoSuchElementException();
692	>	if (next == null)
693	>	throw new NoSuchElementException();
694		return advance();
695		}
696
697		public void remove() {
698	<	QNode p = currentNode;
699	<	QNode prev = prevNode;
602	<	if (prev == null || p == null)
698	>	Node<E> p = curr;
699	>	if (p == null)
700		throw new IllegalStateException();
701		Object x = p.get();
702		if (x != null && x != p && p.compareAndSet(x, p))
703	<	clean(prev, p);
703	>	clean(pcurr, p);
704		}
705		}
706
707		public E peek() {
708		for (;;) {
709	<	QNode h = traversalHead();
710	<	QNode p = h.next;
709	>	Node<E> h = traversalHead();
710	>	Node<E> p = h.next;
711		if (p == null)
712		return null;
713		Object x = p.get();
#	Line 618 | Line 715 | public class LinkedTransferQueue<E> exte
715		if (!p.isData)
716		return null;
717		if (x != null)
718	<	return (E)x;
718	>	return (E) x;
719		}
720		}
721		}
722
723		public boolean isEmpty() {
724		for (;;) {
725	<	QNode h = traversalHead();
726	<	QNode p = h.next;
725	>	Node<E> h = traversalHead();
726	>	Node<E> p = h.next;
727		if (p == null)
728		return true;
729		Object x = p.get();
#	Line 641 | Line 738 | public class LinkedTransferQueue<E> exte
738
739		public boolean hasWaitingConsumer() {
740		for (;;) {
741	<	QNode h = traversalHead();
742	<	QNode p = h.next;
741	>	Node<E> h = traversalHead();
742	>	Node<E> p = h.next;
743		if (p == null)
744		return false;
745		Object x = p.get();
#	Line 664 | Line 761 | public class LinkedTransferQueue<E> exte
761		* @return the number of elements in this queue
762		*/
763		public int size() {
764	<	int count = 0;
765	<	QNode h = traversalHead();
766	<	for (QNode p = h.next; p != null && p.isData; p = p.next) {
767	<	Object x = p.get();
768	<	if (x != null && x != p) {
769	<	if (++count == Integer.MAX_VALUE) // saturated
764	>	for (;;) {
765	>	int count = 0;
766	>	Node<E> pred = traversalHead();
767	>	for (;;) {
768	>	Node<E> q = pred.next;
769	>	if (q == pred) // restart
770		break;
771	+	if (q == null || !q.isData)
772	+	return count;
773	+	Object x = q.get();
774	+	if (x != null && x != q) {
775	+	if (++count == Integer.MAX_VALUE) // saturated
776	+	return count;
777	+	}
778	+	pred = q;
779		}
780		}
676	–	return count;
781		}
782
783		public int getWaitingConsumerCount() {
784	<	int count = 0;
785	<	QNode h = traversalHead();
786	<	for (QNode p = h.next; p != null && !p.isData; p = p.next) {
787	<	if (p.get() == null) {
788	<	if (++count == Integer.MAX_VALUE)
784	>	// converse of size -- count valid non-data nodes
785	>	for (;;) {
786	>	int count = 0;
787	>	Node<E> pred = traversalHead();
788	>	for (;;) {
789	>	Node<E> q = pred.next;
790	>	if (q == pred) // restart
791		break;
792	+	if (q == null || q.isData)
793	+	return count;
794	+	Object x = q.get();
795	+	if (x == null) {
796	+	if (++count == Integer.MAX_VALUE) // saturated
797	+	return count;
798	+	}
799	+	pred = q;
800	+	}
801	+	}
802	+	}
803	+
804	+	public boolean remove(Object o) {
805	+	if (o == null)
806	+	return false;
807	+	for (;;) {
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 false;
815	+	Object x = q.get();
816	+	if (x != null && x != q && o.equals(x) &&
817	+	q.compareAndSet(x, q)) {
818	+	clean(pred, q);
819	+	return true;
820	+	}
821	+	pred = q;
822		}
823		}
688	–	return count;
824		}
825
826		public int remainingCapacity() {
#	Line 702 | Line 837 | public class LinkedTransferQueue<E> exte
837		private void writeObject(java.io.ObjectOutputStream s)
838		throws java.io.IOException {
839		s.defaultWriteObject();
840	<	for (Iterator<E> it = iterator(); it.hasNext(); )
841	<	s.writeObject(it.next());
840	>	for (E e : this)
841	>	s.writeObject(e);
842		// Use trailing null as sentinel
843		s.writeObject(null);
844		}
#	Line 711 | Line 846 | public class LinkedTransferQueue<E> exte
846		/**
847		* Reconstitute the Queue instance from a stream (that is,
848		* deserialize it).
849	+	*
850		* @param s the stream
851		*/
852		private void readObject(java.io.ObjectInputStream s)
#	Line 718 | Line 854 | public class LinkedTransferQueue<E> exte
854		s.defaultReadObject();
855		resetHeadAndTail();
856		for (;;) {
857	<	E item = (E)s.readObject();
857	>	@SuppressWarnings("unchecked") E item = (E) s.readObject();
858		if (item == null)
859		break;
860		else
#	Line 726 | Line 862 | public class LinkedTransferQueue<E> exte
862		}
863		}
864
729	–
865		// Support for resetting head/tail while deserializing
866		private void resetHeadAndTail() {
867	<	QNode dummy = new QNode(null, false);
868	<	_unsafe.putObjectVolatile(this, headOffset,
869	<	new PaddedAtomicReference<QNode>(dummy));
870	<	_unsafe.putObjectVolatile(this, tailOffset,
871	<	new PaddedAtomicReference<QNode>(dummy));
872	<	_unsafe.putObjectVolatile(this, cleanMeOffset,
873	<	new PaddedAtomicReference<QNode>(null));
867	>	Node<E> dummy = new Node<E>(null, false);
868	>	UNSAFE.putObjectVolatile(this, headOffset,
869	>	new PaddedAtomicReference<Node<E>>(dummy));
870	>	UNSAFE.putObjectVolatile(this, tailOffset,
871	>	new PaddedAtomicReference<Node<E>>(dummy));
872	>	UNSAFE.putObjectVolatile(this, cleanMeOffset,
873	>	new PaddedAtomicReference<Node<E>>(null));
874	>	}
875	>
876	>	// Unsafe mechanics
877	>
878	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
879	>	private static final long headOffset =
880	>	objectFieldOffset(UNSAFE, "head", LinkedTransferQueue.class);
881	>	private static final long tailOffset =
882	>	objectFieldOffset(UNSAFE, "tail", LinkedTransferQueue.class);
883	>	private static final long cleanMeOffset =
884	>	objectFieldOffset(UNSAFE, "cleanMe", LinkedTransferQueue.class);
885	>
886	>
887	>	static long objectFieldOffset(sun.misc.Unsafe UNSAFE,
888	>	String field, Class<?> klazz) {
889	>	try {
890	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
891	>	} catch (NoSuchFieldException e) {
892	>	// Convert Exception to corresponding Error
893	>	NoSuchFieldError error = new NoSuchFieldError(field);
894	>	error.initCause(e);
895	>	throw error;
896	>	}
897		}
898
899	<	// Temporary Unsafe mechanics for preliminary release
900	<	private static final Unsafe _unsafe;
901	<	private static final long headOffset;
902	<	private static final long tailOffset;
903	<	private static final long cleanMeOffset;
904	<	static {
899	>	/**
900	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
901	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
902	>	* into a jdk.
903	>	*
904	>	* @return a sun.misc.Unsafe
905	>	*/
906	>	private static sun.misc.Unsafe getUnsafe() {
907		try {
908	<	if (LinkedTransferQueue.class.getClassLoader() != null) {
909	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
910	<	f.setAccessible(true);
911	<	_unsafe = (Unsafe)f.get(null);
908	>	return sun.misc.Unsafe.getUnsafe();
909	>	} catch (SecurityException se) {
910	>	try {
911	>	return java.security.AccessController.doPrivileged
912	>	(new java.security
913	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
914	>	public sun.misc.Unsafe run() throws Exception {
915	>	java.lang.reflect.Field f = sun.misc
916	>	.Unsafe.class.getDeclaredField("theUnsafe");
917	>	f.setAccessible(true);
918	>	return (sun.misc.Unsafe) f.get(null);
919	>	}});
920	>	} catch (java.security.PrivilegedActionException e) {
921	>	throw new RuntimeException("Could not initialize intrinsics",
922	>	e.getCause());
923		}
753	–	else
754	–	_unsafe = Unsafe.getUnsafe();
755	–	headOffset = _unsafe.objectFieldOffset
756	–	(LinkedTransferQueue.class.getDeclaredField("head"));
757	–	tailOffset = _unsafe.objectFieldOffset
758	–	(LinkedTransferQueue.class.getDeclaredField("tail"));
759	–	cleanMeOffset = _unsafe.objectFieldOffset
760	–	(LinkedTransferQueue.class.getDeclaredField("cleanMe"));
761	–	} catch (Exception e) {
762	–	throw new RuntimeException("Could not initialize intrinsics", e);
924		}
925		}
765	–
926		}

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