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 |
> |
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; |
18 |
|
|
19 |
|
/** |
20 |
|
* An unbounded {@linkplain TransferQueue} based on linked nodes. |
47 |
|
* @since 1.7 |
48 |
|
* @author Doug Lea |
49 |
|
* @param <E> the type of elements held in this collection |
47 |
– |
* |
50 |
|
*/ |
51 |
|
public class LinkedTransferQueue<E> extends AbstractQueue<E> |
52 |
|
implements TransferQueue<E>, java.io.Serializable { |
83 |
|
* seems not to vary with number of CPUs (beyond 2) so is just |
84 |
|
* a constant. |
85 |
|
*/ |
86 |
< |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
86 |
> |
static final int maxTimedSpins = (NCPUS < 2) ? 0 : 32; |
87 |
|
|
88 |
|
/** |
89 |
|
* The number of times to spin before blocking in untimed waits. |
105 |
|
* garbage retention. Similarly, setting the next field to this is |
106 |
|
* used as sentinel that node is off list. |
107 |
|
*/ |
108 |
< |
static final class QNode extends AtomicReference<Object> { |
109 |
< |
volatile QNode next; |
108 |
> |
static final class Node<E> extends AtomicReference<Object> { |
109 |
> |
volatile Node<E> next; |
110 |
|
volatile Thread waiter; // to control park/unpark |
111 |
|
final boolean isData; |
112 |
< |
QNode(Object item, boolean isData) { |
112 |
> |
|
113 |
> |
Node(E item, boolean isData) { |
114 |
|
super(item); |
115 |
|
this.isData = isData; |
116 |
|
} |
117 |
|
|
118 |
< |
static final AtomicReferenceFieldUpdater<QNode, QNode> |
118 |
> |
@SuppressWarnings("rawtypes") |
119 |
> |
static final AtomicReferenceFieldUpdater<Node, Node> |
120 |
|
nextUpdater = AtomicReferenceFieldUpdater.newUpdater |
121 |
< |
(QNode.class, QNode.class, "next"); |
121 |
> |
(Node.class, Node.class, "next"); |
122 |
|
|
123 |
< |
boolean casNext(QNode cmp, QNode val) { |
123 |
> |
final boolean casNext(Node<E> cmp, Node<E> val) { |
124 |
|
return nextUpdater.compareAndSet(this, cmp, val); |
125 |
|
} |
126 |
+ |
|
127 |
+ |
final void clearNext() { |
128 |
+ |
nextUpdater.lazySet(this, this); |
129 |
+ |
} |
130 |
+ |
|
131 |
+ |
private static final long serialVersionUID = -3375979862319811754L; |
132 |
|
} |
133 |
|
|
134 |
|
/** |
140 |
|
// enough padding for 64bytes with 4byte refs |
141 |
|
Object p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, pa, pb, pc, pd, pe; |
142 |
|
PaddedAtomicReference(T r) { super(r); } |
143 |
+ |
private static final long serialVersionUID = 8170090609809740854L; |
144 |
|
} |
145 |
|
|
146 |
|
|
147 |
|
/** head of the queue */ |
148 |
< |
private transient final PaddedAtomicReference<QNode> head; |
148 |
> |
private transient final PaddedAtomicReference<Node<E>> head; |
149 |
> |
|
150 |
|
/** tail of the queue */ |
151 |
< |
private transient final PaddedAtomicReference<QNode> tail; |
151 |
> |
private transient final PaddedAtomicReference<Node<E>> tail; |
152 |
|
|
153 |
|
/** |
154 |
|
* Reference to a cancelled node that might not yet have been |
155 |
|
* unlinked from queue because it was the last inserted node |
156 |
|
* when it cancelled. |
157 |
|
*/ |
158 |
< |
private transient final PaddedAtomicReference<QNode> cleanMe; |
158 |
> |
private transient final PaddedAtomicReference<Node<E>> cleanMe; |
159 |
|
|
160 |
|
/** |
161 |
|
* Tries to cas nh as new head; if successful, unlink |
162 |
|
* old head's next node to avoid garbage retention. |
163 |
|
*/ |
164 |
< |
private boolean advanceHead(QNode h, QNode nh) { |
164 |
> |
private boolean advanceHead(Node<E> h, Node<E> nh) { |
165 |
|
if (h == head.get() && head.compareAndSet(h, nh)) { |
166 |
< |
h.next = h; // forget old next |
166 |
> |
h.clearNext(); // forget old next |
167 |
|
return true; |
168 |
|
} |
169 |
|
return false; |
173 |
|
* Puts or takes an item. Used for most queue operations (except |
174 |
|
* poll() and tryTransfer()). See the similar code in |
175 |
|
* SynchronousQueue for detailed explanation. |
176 |
+ |
* |
177 |
|
* @param e the item or if null, signifies that this is a take |
178 |
|
* @param mode the wait mode: NOWAIT, TIMEOUT, WAIT |
179 |
|
* @param nanos timeout in nanosecs, used only if mode is TIMEOUT |
180 |
|
* @return an item, or null on failure |
181 |
|
*/ |
182 |
< |
private Object xfer(Object e, int mode, long nanos) { |
182 |
> |
private E xfer(E e, int mode, long nanos) { |
183 |
|
boolean isData = (e != null); |
184 |
< |
QNode s = null; |
185 |
< |
final PaddedAtomicReference<QNode> head = this.head; |
186 |
< |
final PaddedAtomicReference<QNode> tail = this.tail; |
184 |
> |
Node<E> s = null; |
185 |
> |
final PaddedAtomicReference<Node<E>> head = this.head; |
186 |
> |
final PaddedAtomicReference<Node<E>> tail = this.tail; |
187 |
|
|
188 |
|
for (;;) { |
189 |
< |
QNode t = tail.get(); |
190 |
< |
QNode h = head.get(); |
189 |
> |
Node<E> t = tail.get(); |
190 |
> |
Node<E> h = head.get(); |
191 |
|
|
192 |
|
if (t != null && (t == h || t.isData == isData)) { |
193 |
|
if (s == null) |
194 |
< |
s = new QNode(e, isData); |
195 |
< |
QNode last = t.next; |
194 |
> |
s = new Node<E>(e, isData); |
195 |
> |
Node<E> last = t.next; |
196 |
|
if (last != null) { |
197 |
|
if (t == tail.get()) |
198 |
|
tail.compareAndSet(t, last); |
204 |
|
} |
205 |
|
|
206 |
|
else if (h != null) { |
207 |
< |
QNode first = h.next; |
207 |
> |
Node<E> first = h.next; |
208 |
|
if (t == tail.get() && first != null && |
209 |
|
advanceHead(h, first)) { |
210 |
|
Object x = first.get(); |
211 |
|
if (x != first && first.compareAndSet(x, e)) { |
212 |
|
LockSupport.unpark(first.waiter); |
213 |
< |
return isData? e : x; |
213 |
> |
return isData ? e : (E) x; |
214 |
|
} |
215 |
|
} |
216 |
|
} |
220 |
|
|
221 |
|
/** |
222 |
|
* Version of xfer for poll() and tryTransfer, which |
223 |
< |
* simplifies control paths both here and in xfer |
223 |
> |
* simplifies control paths both here and in xfer. |
224 |
|
*/ |
225 |
< |
private Object fulfill(Object e) { |
225 |
> |
private E fulfill(E e) { |
226 |
|
boolean isData = (e != null); |
227 |
< |
final PaddedAtomicReference<QNode> head = this.head; |
228 |
< |
final PaddedAtomicReference<QNode> tail = this.tail; |
227 |
> |
final PaddedAtomicReference<Node<E>> head = this.head; |
228 |
> |
final PaddedAtomicReference<Node<E>> tail = this.tail; |
229 |
|
|
230 |
|
for (;;) { |
231 |
< |
QNode t = tail.get(); |
232 |
< |
QNode h = head.get(); |
231 |
> |
Node<E> t = tail.get(); |
232 |
> |
Node<E> h = head.get(); |
233 |
|
|
234 |
|
if (t != null && (t == h || t.isData == isData)) { |
235 |
< |
QNode last = t.next; |
235 |
> |
Node<E> last = t.next; |
236 |
|
if (t == tail.get()) { |
237 |
|
if (last != null) |
238 |
|
tail.compareAndSet(t, last); |
241 |
|
} |
242 |
|
} |
243 |
|
else if (h != null) { |
244 |
< |
QNode first = h.next; |
244 |
> |
Node<E> first = h.next; |
245 |
|
if (t == tail.get() && |
246 |
|
first != null && |
247 |
|
advanceHead(h, first)) { |
248 |
|
Object x = first.get(); |
249 |
|
if (x != first && first.compareAndSet(x, e)) { |
250 |
|
LockSupport.unpark(first.waiter); |
251 |
< |
return isData? e : x; |
251 |
> |
return isData ? e : (E) x; |
252 |
|
} |
253 |
|
} |
254 |
|
} |
266 |
|
* @param nanos timeout value |
267 |
|
* @return matched item, or s if cancelled |
268 |
|
*/ |
269 |
< |
private Object awaitFulfill(QNode pred, QNode s, Object e, |
270 |
< |
int mode, long nanos) { |
269 |
> |
private E awaitFulfill(Node<E> pred, Node<E> s, E e, |
270 |
> |
int mode, long nanos) { |
271 |
|
if (mode == NOWAIT) |
272 |
|
return null; |
273 |
|
|
274 |
< |
long lastTime = (mode == TIMEOUT)? System.nanoTime() : 0; |
274 |
> |
long lastTime = (mode == TIMEOUT) ? System.nanoTime() : 0; |
275 |
|
Thread w = Thread.currentThread(); |
276 |
|
int spins = -1; // set to desired spin count below |
277 |
|
for (;;) { |
280 |
|
Object x = s.get(); |
281 |
|
if (x != e) { // Node was matched or cancelled |
282 |
|
advanceHead(pred, s); // unlink if head |
283 |
< |
if (x == s) { // was cancelled |
283 |
> |
if (x == s) { // was cancelled |
284 |
|
clean(pred, s); |
285 |
|
return null; |
286 |
|
} |
287 |
|
else if (x != null) { |
288 |
|
s.set(s); // avoid garbage retention |
289 |
< |
return x; |
289 |
> |
return (E) x; |
290 |
|
} |
291 |
|
else |
292 |
|
return e; |
301 |
|
} |
302 |
|
} |
303 |
|
if (spins < 0) { |
304 |
< |
QNode h = head.get(); // only spin if at head |
304 |
> |
Node<E> h = head.get(); // only spin if at head |
305 |
|
spins = ((h != null && h.next == s) ? |
306 |
< |
(mode == TIMEOUT? |
306 |
> |
((mode == TIMEOUT) ? |
307 |
|
maxTimedSpins : maxUntimedSpins) : 0); |
308 |
|
} |
309 |
|
if (spins > 0) |
324 |
|
} |
325 |
|
|
326 |
|
/** |
327 |
< |
* Returns validated tail for use in cleaning methods |
327 |
> |
* Returns validated tail for use in cleaning methods. |
328 |
|
*/ |
329 |
< |
private QNode getValidatedTail() { |
329 |
> |
private Node<E> getValidatedTail() { |
330 |
|
for (;;) { |
331 |
< |
QNode h = head.get(); |
332 |
< |
QNode first = h.next; |
331 |
> |
Node<E> h = head.get(); |
332 |
> |
Node<E> first = h.next; |
333 |
|
if (first != null && first.next == first) { // help advance |
334 |
|
advanceHead(h, first); |
335 |
|
continue; |
336 |
|
} |
337 |
< |
QNode t = tail.get(); |
338 |
< |
QNode last = t.next; |
337 |
> |
Node<E> t = tail.get(); |
338 |
> |
Node<E> last = t.next; |
339 |
|
if (t == tail.get()) { |
340 |
|
if (last != null) |
341 |
|
tail.compareAndSet(t, last); // help advance |
347 |
|
|
348 |
|
/** |
349 |
|
* Gets rid of cancelled node s with original predecessor pred. |
350 |
+ |
* |
351 |
|
* @param pred predecessor of cancelled node |
352 |
|
* @param s the cancelled node |
353 |
|
*/ |
354 |
< |
private void clean(QNode pred, QNode s) { |
354 |
> |
private void clean(Node<E> pred, Node<E> s) { |
355 |
|
Thread w = s.waiter; |
356 |
|
if (w != null) { // Wake up thread |
357 |
|
s.waiter = null; |
358 |
|
if (w != Thread.currentThread()) |
359 |
|
LockSupport.unpark(w); |
360 |
|
} |
361 |
+ |
|
362 |
+ |
if (pred == null) |
363 |
+ |
return; |
364 |
+ |
|
365 |
|
/* |
366 |
|
* At any given time, exactly one node on list cannot be |
367 |
|
* deleted -- the last inserted node. To accommodate this, if |
371 |
|
* processed, so this always terminates. |
372 |
|
*/ |
373 |
|
while (pred.next == s) { |
374 |
< |
QNode oldpred = reclean(); // First, help get rid of cleanMe |
375 |
< |
QNode t = getValidatedTail(); |
374 |
> |
Node<E> oldpred = reclean(); // First, help get rid of cleanMe |
375 |
> |
Node<E> t = getValidatedTail(); |
376 |
|
if (s != t) { // If not tail, try to unsplice |
377 |
< |
QNode sn = s.next; // s.next == s means s already off list |
377 |
> |
Node<E> sn = s.next; // s.next == s means s already off list |
378 |
|
if (sn == s || pred.casNext(s, sn)) |
379 |
|
break; |
380 |
|
} |
387 |
|
/** |
388 |
|
* Tries to unsplice the cancelled node held in cleanMe that was |
389 |
|
* previously uncleanable because it was at tail. |
390 |
+ |
* |
391 |
|
* @return current cleanMe node (or null) |
392 |
|
*/ |
393 |
< |
private QNode reclean() { |
393 |
> |
private Node<E> reclean() { |
394 |
|
/* |
395 |
|
* cleanMe is, or at one time was, predecessor of cancelled |
396 |
|
* node s that was the tail so could not be unspliced. If s |
402 |
|
* This can loop only due to contention on casNext or |
403 |
|
* clearing cleanMe. |
404 |
|
*/ |
405 |
< |
QNode pred; |
405 |
> |
Node<E> pred; |
406 |
|
while ((pred = cleanMe.get()) != null) { |
407 |
< |
QNode t = getValidatedTail(); |
408 |
< |
QNode s = pred.next; |
407 |
> |
Node<E> t = getValidatedTail(); |
408 |
> |
Node<E> s = pred.next; |
409 |
|
if (s != t) { |
410 |
< |
QNode sn; |
410 |
> |
Node<E> sn; |
411 |
|
if (s == null || s == pred || s.get() != s || |
412 |
|
(sn = s.next) == s || pred.casNext(s, sn)) |
413 |
|
cleanMe.compareAndSet(pred, null); |
422 |
|
* Creates an initially empty {@code LinkedTransferQueue}. |
423 |
|
*/ |
424 |
|
public LinkedTransferQueue() { |
425 |
< |
QNode dummy = new QNode(null, false); |
426 |
< |
head = new PaddedAtomicReference<QNode>(dummy); |
427 |
< |
tail = new PaddedAtomicReference<QNode>(dummy); |
428 |
< |
cleanMe = new PaddedAtomicReference<QNode>(null); |
425 |
> |
Node<E> dummy = new Node<E>(null, false); |
426 |
> |
head = new PaddedAtomicReference<Node<E>>(dummy); |
427 |
> |
tail = new PaddedAtomicReference<Node<E>>(dummy); |
428 |
> |
cleanMe = new PaddedAtomicReference<Node<E>>(null); |
429 |
|
} |
430 |
|
|
431 |
|
/** |
432 |
|
* Creates a {@code LinkedTransferQueue} |
433 |
|
* initially containing the elements of the given collection, |
434 |
|
* added in traversal order of the collection's iterator. |
435 |
+ |
* |
436 |
|
* @param c the collection of elements to initially contain |
437 |
|
* @throws NullPointerException if the specified collection or any |
438 |
|
* of its elements are null |
442 |
|
addAll(c); |
443 |
|
} |
444 |
|
|
445 |
+ |
/** |
446 |
+ |
* @throws InterruptedException {@inheritDoc} |
447 |
+ |
* @throws NullPointerException {@inheritDoc} |
448 |
+ |
*/ |
449 |
|
public void put(E e) throws InterruptedException { |
450 |
|
if (e == null) throw new NullPointerException(); |
451 |
|
if (Thread.interrupted()) throw new InterruptedException(); |
452 |
|
xfer(e, NOWAIT, 0); |
453 |
|
} |
454 |
|
|
455 |
+ |
/** |
456 |
+ |
* @throws InterruptedException {@inheritDoc} |
457 |
+ |
* @throws NullPointerException {@inheritDoc} |
458 |
+ |
*/ |
459 |
|
public boolean offer(E e, long timeout, TimeUnit unit) |
460 |
|
throws InterruptedException { |
461 |
|
if (e == null) throw new NullPointerException(); |
464 |
|
return true; |
465 |
|
} |
466 |
|
|
467 |
+ |
/** |
468 |
+ |
* @throws NullPointerException {@inheritDoc} |
469 |
+ |
*/ |
470 |
|
public boolean offer(E e) { |
471 |
|
if (e == null) throw new NullPointerException(); |
472 |
|
xfer(e, NOWAIT, 0); |
473 |
|
return true; |
474 |
|
} |
475 |
|
|
476 |
+ |
/** |
477 |
+ |
* @throws NullPointerException {@inheritDoc} |
478 |
+ |
*/ |
479 |
+ |
public boolean add(E e) { |
480 |
+ |
if (e == null) throw new NullPointerException(); |
481 |
+ |
xfer(e, NOWAIT, 0); |
482 |
+ |
return true; |
483 |
+ |
} |
484 |
+ |
|
485 |
+ |
/** |
486 |
+ |
* @throws InterruptedException {@inheritDoc} |
487 |
+ |
* @throws NullPointerException {@inheritDoc} |
488 |
+ |
*/ |
489 |
|
public void transfer(E e) throws InterruptedException { |
490 |
|
if (e == null) throw new NullPointerException(); |
491 |
|
if (xfer(e, WAIT, 0) == null) { |
494 |
|
} |
495 |
|
} |
496 |
|
|
497 |
+ |
/** |
498 |
+ |
* @throws InterruptedException {@inheritDoc} |
499 |
+ |
* @throws NullPointerException {@inheritDoc} |
500 |
+ |
*/ |
501 |
|
public boolean tryTransfer(E e, long timeout, TimeUnit unit) |
502 |
|
throws InterruptedException { |
503 |
|
if (e == null) throw new NullPointerException(); |
508 |
|
throw new InterruptedException(); |
509 |
|
} |
510 |
|
|
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 |
+ |
*/ |
522 |
|
public E take() throws InterruptedException { |
523 |
|
Object e = xfer(null, WAIT, 0); |
524 |
|
if (e != null) |
525 |
< |
return (E)e; |
525 |
> |
return (E) e; |
526 |
|
Thread.interrupted(); |
527 |
|
throw new InterruptedException(); |
528 |
|
} |
529 |
|
|
530 |
+ |
/** |
531 |
+ |
* @throws InterruptedException {@inheritDoc} |
532 |
+ |
*/ |
533 |
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
534 |
|
Object e = xfer(null, TIMEOUT, unit.toNanos(timeout)); |
535 |
|
if (e != null || !Thread.interrupted()) |
536 |
< |
return (E)e; |
536 |
> |
return (E) e; |
537 |
|
throw new InterruptedException(); |
538 |
|
} |
539 |
|
|
540 |
|
public E poll() { |
541 |
< |
return (E)fulfill(null); |
541 |
> |
return fulfill(null); |
542 |
|
} |
543 |
|
|
544 |
+ |
/** |
545 |
+ |
* @throws NullPointerException {@inheritDoc} |
546 |
+ |
* @throwsIllegalArgumentException {@inheritDoc} |
547 |
+ |
*/ |
548 |
|
public int drainTo(Collection<? super E> c) { |
549 |
|
if (c == null) |
550 |
|
throw new NullPointerException(); |
559 |
|
return n; |
560 |
|
} |
561 |
|
|
562 |
+ |
/** |
563 |
+ |
* @throws NullPointerException {@inheritDoc} |
564 |
+ |
* @throwsIllegalArgumentException {@inheritDoc} |
565 |
+ |
*/ |
566 |
|
public int drainTo(Collection<? super E> c, int maxElements) { |
567 |
|
if (c == null) |
568 |
|
throw new NullPointerException(); |
580 |
|
// Traversal-based methods |
581 |
|
|
582 |
|
/** |
583 |
< |
* Return head after performing any outstanding helping steps |
583 |
> |
* Returns head after performing any outstanding helping steps. |
584 |
|
*/ |
585 |
< |
private QNode traversalHead() { |
585 |
> |
private Node<E> traversalHead() { |
586 |
|
for (;;) { |
587 |
< |
QNode t = tail.get(); |
588 |
< |
QNode h = head.get(); |
587 |
> |
Node<E> t = tail.get(); |
588 |
> |
Node<E> h = head.get(); |
589 |
|
if (h != null && t != null) { |
590 |
< |
QNode last = t.next; |
591 |
< |
QNode first = h.next; |
590 |
> |
Node<E> last = t.next; |
591 |
> |
Node<E> first = h.next; |
592 |
|
if (t == tail.get()) { |
593 |
|
if (last != null) |
594 |
|
tail.compareAndSet(t, last); |
603 |
|
return h; |
604 |
|
} |
605 |
|
} |
606 |
+ |
reclean(); |
607 |
|
} |
608 |
|
} |
609 |
|
|
620 |
|
* if subsequently removed. |
621 |
|
*/ |
622 |
|
class Itr implements Iterator<E> { |
623 |
< |
QNode nextNode; // Next node to return next |
624 |
< |
QNode currentNode; // last returned node, for remove() |
625 |
< |
QNode prevNode; // predecessor of last returned node |
626 |
< |
E nextItem; // Cache of next item, once commited to in next |
623 |
> |
Node<E> next; // node to return next |
624 |
> |
Node<E> pnext; // predecessor of next |
625 |
> |
Node<E> snext; // successor of next |
626 |
> |
Node<E> curr; // last returned node, for remove() |
627 |
> |
Node<E> pcurr; // predecessor of curr, for remove() |
628 |
> |
E nextItem; // Cache of next item, once committed to in next |
629 |
|
|
630 |
|
Itr() { |
631 |
< |
nextNode = traversalHead(); |
564 |
< |
advance(); |
631 |
> |
findNext(); |
632 |
|
} |
633 |
|
|
634 |
< |
E advance() { |
635 |
< |
prevNode = currentNode; |
636 |
< |
currentNode = nextNode; |
637 |
< |
E x = nextItem; |
571 |
< |
|
572 |
< |
QNode p = nextNode.next; |
634 |
> |
/** |
635 |
> |
* Ensures next points to next valid node, or null if none. |
636 |
> |
*/ |
637 |
> |
void findNext() { |
638 |
|
for (;;) { |
639 |
< |
if (p == null || !p.isData) { |
640 |
< |
nextNode = null; |
641 |
< |
nextItem = null; |
642 |
< |
return x; |
643 |
< |
} |
644 |
< |
Object item = p.get(); |
645 |
< |
if (item != p && item != null) { |
646 |
< |
nextNode = p; |
647 |
< |
nextItem = (E)item; |
648 |
< |
return x; |
639 |
> |
Node<E> pred = pnext; |
640 |
> |
Node<E> q = next; |
641 |
> |
if (pred == null || pred == q) { |
642 |
> |
pred = traversalHead(); |
643 |
> |
q = pred.next; |
644 |
> |
} |
645 |
> |
if (q == null || !q.isData) { |
646 |
> |
next = null; |
647 |
> |
return; |
648 |
> |
} |
649 |
> |
Object x = q.get(); |
650 |
> |
Node<E> s = q.next; |
651 |
> |
if (x != null && q != x && q != s) { |
652 |
> |
nextItem = (E) x; |
653 |
> |
snext = s; |
654 |
> |
pnext = pred; |
655 |
> |
next = q; |
656 |
> |
return; |
657 |
|
} |
658 |
< |
prevNode = p; |
659 |
< |
p = p.next; |
658 |
> |
pnext = q; |
659 |
> |
next = s; |
660 |
|
} |
661 |
|
} |
662 |
|
|
663 |
|
public boolean hasNext() { |
664 |
< |
return nextNode != null; |
664 |
> |
return next != null; |
665 |
|
} |
666 |
|
|
667 |
|
public E next() { |
668 |
< |
if (nextNode == null) throw new NoSuchElementException(); |
669 |
< |
return advance(); |
668 |
> |
if (next == null) throw new NoSuchElementException(); |
669 |
> |
pcurr = pnext; |
670 |
> |
curr = next; |
671 |
> |
pnext = next; |
672 |
> |
next = snext; |
673 |
> |
E x = nextItem; |
674 |
> |
findNext(); |
675 |
> |
return x; |
676 |
|
} |
677 |
|
|
678 |
|
public void remove() { |
679 |
< |
QNode p = currentNode; |
680 |
< |
QNode prev = prevNode; |
602 |
< |
if (prev == null || p == null) |
679 |
> |
Node<E> p = curr; |
680 |
> |
if (p == null) |
681 |
|
throw new IllegalStateException(); |
682 |
|
Object x = p.get(); |
683 |
|
if (x != null && x != p && p.compareAndSet(x, p)) |
684 |
< |
clean(prev, p); |
684 |
> |
clean(pcurr, p); |
685 |
|
} |
686 |
|
} |
687 |
|
|
688 |
|
public E peek() { |
689 |
|
for (;;) { |
690 |
< |
QNode h = traversalHead(); |
691 |
< |
QNode p = h.next; |
690 |
> |
Node<E> h = traversalHead(); |
691 |
> |
Node<E> p = h.next; |
692 |
|
if (p == null) |
693 |
|
return null; |
694 |
|
Object x = p.get(); |
696 |
|
if (!p.isData) |
697 |
|
return null; |
698 |
|
if (x != null) |
699 |
< |
return (E)x; |
699 |
> |
return (E) x; |
700 |
|
} |
701 |
|
} |
702 |
|
} |
703 |
|
|
704 |
|
public boolean isEmpty() { |
705 |
|
for (;;) { |
706 |
< |
QNode h = traversalHead(); |
707 |
< |
QNode p = h.next; |
706 |
> |
Node<E> h = traversalHead(); |
707 |
> |
Node<E> p = h.next; |
708 |
|
if (p == null) |
709 |
|
return true; |
710 |
|
Object x = p.get(); |
719 |
|
|
720 |
|
public boolean hasWaitingConsumer() { |
721 |
|
for (;;) { |
722 |
< |
QNode h = traversalHead(); |
723 |
< |
QNode p = h.next; |
722 |
> |
Node<E> h = traversalHead(); |
723 |
> |
Node<E> p = h.next; |
724 |
|
if (p == null) |
725 |
|
return false; |
726 |
|
Object x = p.get(); |
743 |
|
*/ |
744 |
|
public int size() { |
745 |
|
int count = 0; |
746 |
< |
QNode h = traversalHead(); |
747 |
< |
for (QNode p = h.next; p != null && p.isData; p = p.next) { |
746 |
> |
Node<E> h = traversalHead(); |
747 |
> |
for (Node<E> p = h.next; p != null && p.isData; p = p.next) { |
748 |
|
Object x = p.get(); |
749 |
|
if (x != null && x != p) { |
750 |
|
if (++count == Integer.MAX_VALUE) // saturated |
756 |
|
|
757 |
|
public int getWaitingConsumerCount() { |
758 |
|
int count = 0; |
759 |
< |
QNode h = traversalHead(); |
760 |
< |
for (QNode p = h.next; p != null && !p.isData; p = p.next) { |
759 |
> |
Node<E> h = traversalHead(); |
760 |
> |
for (Node<E> p = h.next; p != null && !p.isData; p = p.next) { |
761 |
|
if (p.get() == null) { |
762 |
|
if (++count == Integer.MAX_VALUE) |
763 |
|
break; |
770 |
|
return Integer.MAX_VALUE; |
771 |
|
} |
772 |
|
|
773 |
+ |
public boolean remove(Object o) { |
774 |
+ |
if (o == null) |
775 |
+ |
return false; |
776 |
+ |
for (;;) { |
777 |
+ |
Node<E> pred = traversalHead(); |
778 |
+ |
for (;;) { |
779 |
+ |
Node<E> q = pred.next; |
780 |
+ |
if (q == null || !q.isData) |
781 |
+ |
return false; |
782 |
+ |
if (q == pred) // restart |
783 |
+ |
break; |
784 |
+ |
Object x = q.get(); |
785 |
+ |
if (x != null && x != q && o.equals(x) && |
786 |
+ |
q.compareAndSet(x, q)) { |
787 |
+ |
clean(pred, q); |
788 |
+ |
return true; |
789 |
+ |
} |
790 |
+ |
pred = q; |
791 |
+ |
} |
792 |
+ |
} |
793 |
+ |
} |
794 |
+ |
|
795 |
|
/** |
796 |
|
* Save the state to a stream (that is, serialize it). |
797 |
|
* |
802 |
|
private void writeObject(java.io.ObjectOutputStream s) |
803 |
|
throws java.io.IOException { |
804 |
|
s.defaultWriteObject(); |
805 |
< |
for (Iterator<E> it = iterator(); it.hasNext(); ) |
806 |
< |
s.writeObject(it.next()); |
805 |
> |
for (E e : this) |
806 |
> |
s.writeObject(e); |
807 |
|
// Use trailing null as sentinel |
808 |
|
s.writeObject(null); |
809 |
|
} |
811 |
|
/** |
812 |
|
* Reconstitute the Queue instance from a stream (that is, |
813 |
|
* deserialize it). |
814 |
+ |
* |
815 |
|
* @param s the stream |
816 |
|
*/ |
817 |
|
private void readObject(java.io.ObjectInputStream s) |
819 |
|
s.defaultReadObject(); |
820 |
|
resetHeadAndTail(); |
821 |
|
for (;;) { |
822 |
< |
E item = (E)s.readObject(); |
822 |
> |
@SuppressWarnings("unchecked") E item = (E) s.readObject(); |
823 |
|
if (item == null) |
824 |
|
break; |
825 |
|
else |
827 |
|
} |
828 |
|
} |
829 |
|
|
729 |
– |
|
830 |
|
// Support for resetting head/tail while deserializing |
831 |
|
private void resetHeadAndTail() { |
832 |
< |
QNode dummy = new QNode(null, false); |
833 |
< |
_unsafe.putObjectVolatile(this, headOffset, |
834 |
< |
new PaddedAtomicReference<QNode>(dummy)); |
835 |
< |
_unsafe.putObjectVolatile(this, tailOffset, |
836 |
< |
new PaddedAtomicReference<QNode>(dummy)); |
837 |
< |
_unsafe.putObjectVolatile(this, cleanMeOffset, |
838 |
< |
new PaddedAtomicReference<QNode>(null)); |
832 |
> |
Node<E> dummy = new Node<E>(null, false); |
833 |
> |
UNSAFE.putObjectVolatile(this, headOffset, |
834 |
> |
new PaddedAtomicReference<Node<E>>(dummy)); |
835 |
> |
UNSAFE.putObjectVolatile(this, tailOffset, |
836 |
> |
new PaddedAtomicReference<Node<E>>(dummy)); |
837 |
> |
UNSAFE.putObjectVolatile(this, cleanMeOffset, |
838 |
> |
new PaddedAtomicReference<Node<E>>(null)); |
839 |
> |
} |
840 |
> |
|
841 |
> |
// Unsafe mechanics |
842 |
> |
|
843 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
844 |
> |
private static final long headOffset = |
845 |
> |
objectFieldOffset("head", LinkedTransferQueue.class); |
846 |
> |
private static final long tailOffset = |
847 |
> |
objectFieldOffset("tail", LinkedTransferQueue.class); |
848 |
> |
private static final long cleanMeOffset = |
849 |
> |
objectFieldOffset("cleanMe", LinkedTransferQueue.class); |
850 |
> |
|
851 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
852 |
> |
try { |
853 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
854 |
> |
} catch (NoSuchFieldException e) { |
855 |
> |
// Convert Exception to corresponding Error |
856 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
857 |
> |
error.initCause(e); |
858 |
> |
throw error; |
859 |
> |
} |
860 |
|
} |
861 |
|
|
862 |
< |
// Temporary Unsafe mechanics for preliminary release |
863 |
< |
private static final Unsafe _unsafe; |
864 |
< |
private static final long headOffset; |
865 |
< |
private static final long tailOffset; |
866 |
< |
private static final long cleanMeOffset; |
867 |
< |
static { |
862 |
> |
/** |
863 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
864 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
865 |
> |
* into a jdk. |
866 |
> |
* |
867 |
> |
* @return a sun.misc.Unsafe |
868 |
> |
*/ |
869 |
> |
private static sun.misc.Unsafe getUnsafe() { |
870 |
|
try { |
871 |
< |
if (LinkedTransferQueue.class.getClassLoader() != null) { |
872 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
873 |
< |
f.setAccessible(true); |
874 |
< |
_unsafe = (Unsafe)f.get(null); |
871 |
> |
return sun.misc.Unsafe.getUnsafe(); |
872 |
> |
} catch (SecurityException se) { |
873 |
> |
try { |
874 |
> |
return java.security.AccessController.doPrivileged |
875 |
> |
(new java.security |
876 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
877 |
> |
public sun.misc.Unsafe run() throws Exception { |
878 |
> |
java.lang.reflect.Field f = sun.misc |
879 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
880 |
> |
f.setAccessible(true); |
881 |
> |
return (sun.misc.Unsafe) f.get(null); |
882 |
> |
}}); |
883 |
> |
} catch (java.security.PrivilegedActionException e) { |
884 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
885 |
> |
e.getCause()); |
886 |
|
} |
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); |
887 |
|
} |
888 |
|
} |
765 |
– |
|
889 |
|
} |