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.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; |
19 |
|
|
20 |
|
/** |
21 |
|
* An unbounded {@linkplain TransferQueue} based on linked nodes. |
25 |
|
* producer. The <em>tail</em> of the queue is that element that has |
26 |
|
* been on the queue the shortest time for some producer. |
27 |
|
* |
28 |
< |
* <p>Beware that, unlike in most collections, the <tt>size</tt> |
28 |
> |
* <p>Beware that, unlike in most collections, the {@code size} |
29 |
|
* method is <em>NOT</em> a constant-time operation. Because of the |
30 |
|
* asynchronous nature of these queues, determining the current number |
31 |
|
* of elements requires a traversal of the elements. |
48 |
|
* @since 1.7 |
49 |
|
* @author Doug Lea |
50 |
|
* @param <E> the type of elements held in this collection |
47 |
– |
* |
51 |
|
*/ |
52 |
|
public class LinkedTransferQueue<E> extends AbstractQueue<E> |
53 |
|
implements TransferQueue<E>, java.io.Serializable { |
84 |
|
* seems not to vary with number of CPUs (beyond 2) so is just |
85 |
|
* a constant. |
86 |
|
*/ |
87 |
< |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
87 |
> |
static final int maxTimedSpins = (NCPUS < 2) ? 0 : 32; |
88 |
|
|
89 |
|
/** |
90 |
|
* The number of times to spin before blocking in untimed waits. |
106 |
|
* garbage retention. Similarly, setting the next field to this is |
107 |
|
* used as sentinel that node is off list. |
108 |
|
*/ |
109 |
< |
static final class QNode extends AtomicReference<Object> { |
110 |
< |
volatile QNode next; |
109 |
> |
static final class Node<E> extends AtomicReference<Object> { |
110 |
> |
volatile Node<E> next; |
111 |
|
volatile Thread waiter; // to control park/unpark |
112 |
|
final boolean isData; |
113 |
< |
QNode(Object item, boolean isData) { |
113 |
> |
|
114 |
> |
Node(E item, boolean isData) { |
115 |
|
super(item); |
116 |
|
this.isData = isData; |
117 |
|
} |
118 |
|
|
119 |
< |
static final AtomicReferenceFieldUpdater<QNode, QNode> |
116 |
< |
nextUpdater = AtomicReferenceFieldUpdater.newUpdater |
117 |
< |
(QNode.class, QNode.class, "next"); |
119 |
> |
// Unsafe mechanics |
120 |
|
|
121 |
< |
boolean casNext(QNode cmp, QNode val) { |
122 |
< |
return nextUpdater.compareAndSet(this, cmp, val); |
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 UNSAFE.compareAndSwapObject(this, nextOffset, cmp, val); |
127 |
> |
} |
128 |
> |
|
129 |
> |
final void clearNext() { |
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; |
162 |
|
} |
163 |
|
|
164 |
|
/** |
170 |
|
// enough padding for 64bytes with 4byte refs |
171 |
|
Object p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, pa, pb, pc, pd, pe; |
172 |
|
PaddedAtomicReference(T r) { super(r); } |
173 |
+ |
private static final long serialVersionUID = 8170090609809740854L; |
174 |
|
} |
175 |
|
|
176 |
|
|
177 |
|
/** head of the queue */ |
178 |
< |
private transient final PaddedAtomicReference<QNode> head; |
178 |
> |
private transient final PaddedAtomicReference<Node<E>> head; |
179 |
> |
|
180 |
|
/** tail of the queue */ |
181 |
< |
private transient final PaddedAtomicReference<QNode> tail; |
181 |
> |
private transient final PaddedAtomicReference<Node<E>> tail; |
182 |
|
|
183 |
|
/** |
184 |
|
* Reference to a cancelled node that might not yet have been |
185 |
|
* unlinked from queue because it was the last inserted node |
186 |
|
* when it cancelled. |
187 |
|
*/ |
188 |
< |
private transient final PaddedAtomicReference<QNode> cleanMe; |
188 |
> |
private transient final PaddedAtomicReference<Node<E>> cleanMe; |
189 |
|
|
190 |
|
/** |
191 |
|
* Tries to cas nh as new head; if successful, unlink |
192 |
|
* old head's next node to avoid garbage retention. |
193 |
|
*/ |
194 |
< |
private boolean advanceHead(QNode h, QNode nh) { |
194 |
> |
private boolean advanceHead(Node<E> h, Node<E> nh) { |
195 |
|
if (h == head.get() && head.compareAndSet(h, nh)) { |
196 |
< |
h.next = h; // forget old next |
196 |
> |
h.clearNext(); // forget old next |
197 |
|
return true; |
198 |
|
} |
199 |
|
return false; |
203 |
|
* Puts or takes an item. Used for most queue operations (except |
204 |
|
* poll() and tryTransfer()). See the similar code in |
205 |
|
* SynchronousQueue for detailed explanation. |
206 |
+ |
* |
207 |
|
* @param e the item or if null, signifies that this is a take |
208 |
|
* @param mode the wait mode: NOWAIT, TIMEOUT, WAIT |
209 |
|
* @param nanos timeout in nanosecs, used only if mode is TIMEOUT |
210 |
|
* @return an item, or null on failure |
211 |
|
*/ |
212 |
< |
private Object xfer(Object e, int mode, long nanos) { |
212 |
> |
private E xfer(E e, int mode, long nanos) { |
213 |
|
boolean isData = (e != null); |
214 |
< |
QNode s = null; |
215 |
< |
final PaddedAtomicReference<QNode> head = this.head; |
216 |
< |
final PaddedAtomicReference<QNode> tail = this.tail; |
214 |
> |
Node<E> s = null; |
215 |
> |
final PaddedAtomicReference<Node<E>> head = this.head; |
216 |
> |
final PaddedAtomicReference<Node<E>> tail = this.tail; |
217 |
|
|
218 |
|
for (;;) { |
219 |
< |
QNode t = tail.get(); |
220 |
< |
QNode h = head.get(); |
219 |
> |
Node<E> t = tail.get(); |
220 |
> |
Node<E> h = head.get(); |
221 |
|
|
222 |
|
if (t != null && (t == h || t.isData == isData)) { |
223 |
|
if (s == null) |
224 |
< |
s = new QNode(e, isData); |
225 |
< |
QNode last = t.next; |
224 |
> |
s = new Node<E>(e, isData); |
225 |
> |
Node<E> last = t.next; |
226 |
|
if (last != null) { |
227 |
|
if (t == tail.get()) |
228 |
|
tail.compareAndSet(t, last); |
234 |
|
} |
235 |
|
|
236 |
|
else if (h != null) { |
237 |
< |
QNode first = h.next; |
237 |
> |
Node<E> first = h.next; |
238 |
|
if (t == tail.get() && first != null && |
239 |
|
advanceHead(h, first)) { |
240 |
|
Object x = first.get(); |
241 |
|
if (x != first && first.compareAndSet(x, e)) { |
242 |
|
LockSupport.unpark(first.waiter); |
243 |
< |
return isData? e : x; |
243 |
> |
return isData ? e : (E) x; |
244 |
|
} |
245 |
|
} |
246 |
|
} |
250 |
|
|
251 |
|
/** |
252 |
|
* Version of xfer for poll() and tryTransfer, which |
253 |
< |
* simplifies control paths both here and in xfer |
253 |
> |
* simplifies control paths both here and in xfer. |
254 |
|
*/ |
255 |
< |
private Object fulfill(Object e) { |
255 |
> |
private E fulfill(E e) { |
256 |
|
boolean isData = (e != null); |
257 |
< |
final PaddedAtomicReference<QNode> head = this.head; |
258 |
< |
final PaddedAtomicReference<QNode> tail = this.tail; |
257 |
> |
final PaddedAtomicReference<Node<E>> head = this.head; |
258 |
> |
final PaddedAtomicReference<Node<E>> tail = this.tail; |
259 |
|
|
260 |
|
for (;;) { |
261 |
< |
QNode t = tail.get(); |
262 |
< |
QNode h = head.get(); |
261 |
> |
Node<E> t = tail.get(); |
262 |
> |
Node<E> h = head.get(); |
263 |
|
|
264 |
|
if (t != null && (t == h || t.isData == isData)) { |
265 |
< |
QNode last = t.next; |
265 |
> |
Node<E> last = t.next; |
266 |
|
if (t == tail.get()) { |
267 |
|
if (last != null) |
268 |
|
tail.compareAndSet(t, last); |
271 |
|
} |
272 |
|
} |
273 |
|
else if (h != null) { |
274 |
< |
QNode first = h.next; |
274 |
> |
Node<E> first = h.next; |
275 |
|
if (t == tail.get() && |
276 |
|
first != null && |
277 |
|
advanceHead(h, first)) { |
278 |
|
Object x = first.get(); |
279 |
|
if (x != first && first.compareAndSet(x, e)) { |
280 |
|
LockSupport.unpark(first.waiter); |
281 |
< |
return isData? e : x; |
281 |
> |
return isData ? e : (E) x; |
282 |
|
} |
283 |
|
} |
284 |
|
} |
296 |
|
* @param nanos timeout value |
297 |
|
* @return matched item, or s if cancelled |
298 |
|
*/ |
299 |
< |
private Object awaitFulfill(QNode pred, QNode s, Object e, |
300 |
< |
int mode, long nanos) { |
299 |
> |
private E awaitFulfill(Node<E> pred, Node<E> s, E e, |
300 |
> |
int mode, long nanos) { |
301 |
|
if (mode == NOWAIT) |
302 |
|
return null; |
303 |
|
|
304 |
< |
long lastTime = (mode == TIMEOUT)? System.nanoTime() : 0; |
304 |
> |
long lastTime = (mode == TIMEOUT) ? System.nanoTime() : 0; |
305 |
|
Thread w = Thread.currentThread(); |
306 |
|
int spins = -1; // set to desired spin count below |
307 |
|
for (;;) { |
310 |
|
Object x = s.get(); |
311 |
|
if (x != e) { // Node was matched or cancelled |
312 |
|
advanceHead(pred, s); // unlink if head |
313 |
< |
if (x == s) { // was cancelled |
313 |
> |
if (x == s) { // was cancelled |
314 |
|
clean(pred, s); |
315 |
|
return null; |
316 |
|
} |
317 |
|
else if (x != null) { |
318 |
|
s.set(s); // avoid garbage retention |
319 |
< |
return x; |
319 |
> |
return (E) x; |
320 |
|
} |
321 |
|
else |
322 |
|
return e; |
331 |
|
} |
332 |
|
} |
333 |
|
if (spins < 0) { |
334 |
< |
QNode h = head.get(); // only spin if at head |
334 |
> |
Node<E> h = head.get(); // only spin if at head |
335 |
|
spins = ((h != null && h.next == s) ? |
336 |
< |
(mode == TIMEOUT? |
336 |
> |
((mode == TIMEOUT) ? |
337 |
|
maxTimedSpins : maxUntimedSpins) : 0); |
338 |
|
} |
339 |
|
if (spins > 0) |
341 |
|
else if (s.waiter == null) |
342 |
|
s.waiter = w; |
343 |
|
else if (mode != TIMEOUT) { |
344 |
< |
// LockSupport.park(this); |
302 |
< |
LockSupport.park(); // allows run on java5 |
344 |
> |
LockSupport.park(this); |
345 |
|
s.waiter = null; |
346 |
|
spins = -1; |
347 |
|
} |
348 |
|
else if (nanos > spinForTimeoutThreshold) { |
349 |
< |
// LockSupport.parkNanos(this, nanos); |
308 |
< |
LockSupport.parkNanos(nanos); |
349 |
> |
LockSupport.parkNanos(this, nanos); |
350 |
|
s.waiter = null; |
351 |
|
spins = -1; |
352 |
|
} |
354 |
|
} |
355 |
|
|
356 |
|
/** |
357 |
< |
* Returns validated tail for use in cleaning methods |
357 |
> |
* Returns validated tail for use in cleaning methods. |
358 |
|
*/ |
359 |
< |
private QNode getValidatedTail() { |
359 |
> |
private Node<E> getValidatedTail() { |
360 |
|
for (;;) { |
361 |
< |
QNode h = head.get(); |
362 |
< |
QNode first = h.next; |
361 |
> |
Node<E> h = head.get(); |
362 |
> |
Node<E> first = h.next; |
363 |
|
if (first != null && first.next == first) { // help advance |
364 |
|
advanceHead(h, first); |
365 |
|
continue; |
366 |
|
} |
367 |
< |
QNode t = tail.get(); |
368 |
< |
QNode last = t.next; |
367 |
> |
Node<E> t = tail.get(); |
368 |
> |
Node<E> last = t.next; |
369 |
|
if (t == tail.get()) { |
370 |
|
if (last != null) |
371 |
|
tail.compareAndSet(t, last); // help advance |
373 |
|
return t; |
374 |
|
} |
375 |
|
} |
376 |
< |
} |
376 |
> |
} |
377 |
|
|
378 |
|
/** |
379 |
|
* Gets rid of cancelled node s with original predecessor pred. |
380 |
+ |
* |
381 |
|
* @param pred predecessor of cancelled node |
382 |
|
* @param s the cancelled node |
383 |
|
*/ |
384 |
< |
private void clean(QNode pred, QNode s) { |
384 |
> |
private void clean(Node<E> pred, Node<E> s) { |
385 |
|
Thread w = s.waiter; |
386 |
|
if (w != null) { // Wake up thread |
387 |
|
s.waiter = null; |
388 |
|
if (w != Thread.currentThread()) |
389 |
|
LockSupport.unpark(w); |
390 |
|
} |
391 |
+ |
|
392 |
+ |
if (pred == null) |
393 |
+ |
return; |
394 |
+ |
|
395 |
|
/* |
396 |
|
* At any given time, exactly one node on list cannot be |
397 |
|
* deleted -- the last inserted node. To accommodate this, if |
401 |
|
* processed, so this always terminates. |
402 |
|
*/ |
403 |
|
while (pred.next == s) { |
404 |
< |
QNode oldpred = reclean(); // First, help get rid of cleanMe |
405 |
< |
QNode t = getValidatedTail(); |
404 |
> |
Node<E> oldpred = reclean(); // First, help get rid of cleanMe |
405 |
> |
Node<E> t = getValidatedTail(); |
406 |
|
if (s != t) { // If not tail, try to unsplice |
407 |
< |
QNode sn = s.next; // s.next == s means s already off list |
408 |
< |
if (sn == s || pred.casNext(s, sn)) |
407 |
> |
Node<E> sn = s.next; // s.next == s means s already off list |
408 |
> |
if (sn == s || pred.casNext(s, sn)) |
409 |
|
break; |
410 |
|
} |
411 |
|
else if (oldpred == pred || // Already saved |
417 |
|
/** |
418 |
|
* Tries to unsplice the cancelled node held in cleanMe that was |
419 |
|
* previously uncleanable because it was at tail. |
420 |
+ |
* |
421 |
|
* @return current cleanMe node (or null) |
422 |
|
*/ |
423 |
< |
private QNode reclean() { |
424 |
< |
/* |
423 |
> |
private Node<E> reclean() { |
424 |
> |
/* |
425 |
|
* cleanMe is, or at one time was, predecessor of cancelled |
426 |
|
* node s that was the tail so could not be unspliced. If s |
427 |
|
* is no longer the tail, try to unsplice if necessary and |
430 |
|
* points to a cancelled node that must be unspliced -- if |
431 |
|
* not, we can (must) clear cleanMe without unsplicing. |
432 |
|
* This can loop only due to contention on casNext or |
433 |
< |
* clearing cleanMe. |
433 |
> |
* clearing cleanMe. |
434 |
|
*/ |
435 |
< |
QNode pred; |
435 |
> |
Node<E> pred; |
436 |
|
while ((pred = cleanMe.get()) != null) { |
437 |
< |
QNode t = getValidatedTail(); |
438 |
< |
QNode s = pred.next; |
439 |
< |
if (s != t) { |
440 |
< |
QNode sn; |
437 |
> |
Node<E> t = getValidatedTail(); |
438 |
> |
Node<E> s = pred.next; |
439 |
> |
if (s != t) { |
440 |
> |
Node<E> sn; |
441 |
|
if (s == null || s == pred || s.get() != s || |
442 |
|
(sn = s.next) == s || pred.casNext(s, sn)) |
443 |
|
cleanMe.compareAndSet(pred, null); |
449 |
|
} |
450 |
|
|
451 |
|
/** |
452 |
< |
* Creates an initially empty <tt>LinkedTransferQueue</tt>. |
452 |
> |
* Creates an initially empty {@code LinkedTransferQueue}. |
453 |
|
*/ |
454 |
|
public LinkedTransferQueue() { |
455 |
< |
QNode dummy = new QNode(null, false); |
456 |
< |
head = new PaddedAtomicReference<QNode>(dummy); |
457 |
< |
tail = new PaddedAtomicReference<QNode>(dummy); |
458 |
< |
cleanMe = new PaddedAtomicReference<QNode>(null); |
455 |
> |
Node<E> dummy = new Node<E>(null, false); |
456 |
> |
head = new PaddedAtomicReference<Node<E>>(dummy); |
457 |
> |
tail = new PaddedAtomicReference<Node<E>>(dummy); |
458 |
> |
cleanMe = new PaddedAtomicReference<Node<E>>(null); |
459 |
|
} |
460 |
|
|
461 |
|
/** |
462 |
< |
* Creates a <tt>LinkedTransferQueue</tt> |
462 |
> |
* Creates a {@code LinkedTransferQueue} |
463 |
|
* initially containing the elements of the given collection, |
464 |
|
* added in traversal order of the collection's iterator. |
465 |
+ |
* |
466 |
|
* @param c the collection of elements to initially contain |
467 |
|
* @throws NullPointerException if the specified collection or any |
468 |
|
* of its elements are null |
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 |
+ |
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) { |
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(); |
568 |
|
throw new InterruptedException(); |
569 |
|
} |
570 |
|
|
465 |
– |
public boolean tryTransfer(E e) { |
466 |
– |
if (e == null) throw new NullPointerException(); |
467 |
– |
return fulfill(e) != null; |
468 |
– |
} |
469 |
– |
|
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 |
|
|
589 |
|
public E poll() { |
590 |
< |
return (E)fulfill(null); |
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(); |
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(); |
629 |
|
// Traversal-based methods |
630 |
|
|
631 |
|
/** |
632 |
< |
* Return head after performing any outstanding helping steps |
632 |
> |
* Returns head after performing any outstanding helping steps. |
633 |
|
*/ |
634 |
< |
private QNode traversalHead() { |
634 |
> |
private Node<E> traversalHead() { |
635 |
|
for (;;) { |
636 |
< |
QNode t = tail.get(); |
637 |
< |
QNode h = head.get(); |
636 |
> |
Node<E> t = tail.get(); |
637 |
> |
Node<E> h = head.get(); |
638 |
|
if (h != null && t != null) { |
639 |
< |
QNode last = t.next; |
640 |
< |
QNode first = h.next; |
639 |
> |
Node<E> last = t.next; |
640 |
> |
Node<E> first = h.next; |
641 |
|
if (t == tail.get()) { |
642 |
|
if (last != null) |
643 |
|
tail.compareAndSet(t, last); |
652 |
|
return h; |
653 |
|
} |
654 |
|
} |
655 |
+ |
reclean(); |
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 |
|
} |
681 |
|
* if subsequently removed. |
682 |
|
*/ |
683 |
|
class Itr implements Iterator<E> { |
684 |
< |
QNode nextNode; // Next node to return next |
685 |
< |
QNode currentNode; // last returned node, for remove() |
686 |
< |
QNode prevNode; // predecessor of last returned node |
687 |
< |
E nextItem; // Cache of next item, once commited to in next |
684 |
> |
Node<E> next; // node to return next |
685 |
> |
Node<E> pnext; // predecessor 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 |
689 |
|
|
690 |
|
Itr() { |
565 |
– |
nextNode = traversalHead(); |
691 |
|
advance(); |
692 |
|
} |
693 |
|
|
694 |
< |
E advance() { |
695 |
< |
prevNode = currentNode; |
696 |
< |
currentNode = nextNode; |
697 |
< |
E x = nextItem; |
694 |
> |
/** |
695 |
> |
* Moves to next valid node and returns item to return for |
696 |
> |
* next(), or null if no such. |
697 |
> |
*/ |
698 |
> |
private E advance() { |
699 |
> |
pcurr = pnext; |
700 |
> |
curr = next; |
701 |
> |
E item = nextItem; |
702 |
|
|
574 |
– |
QNode p = nextNode.next; |
703 |
|
for (;;) { |
704 |
< |
if (p == null || !p.isData) { |
705 |
< |
nextNode = null; |
706 |
< |
nextItem = null; |
707 |
< |
return x; |
708 |
< |
} |
709 |
< |
Object item = p.get(); |
710 |
< |
if (item != p && item != null) { |
711 |
< |
nextNode = p; |
712 |
< |
nextItem = (E)item; |
713 |
< |
return x; |
704 |
> |
pnext = (next == null) ? traversalHead() : next; |
705 |
> |
next = pnext.next; |
706 |
> |
if (next == pnext) { |
707 |
> |
next = null; |
708 |
> |
continue; // restart |
709 |
> |
} |
710 |
> |
if (next == null) |
711 |
> |
break; |
712 |
> |
Object x = next.get(); |
713 |
> |
if (x != null && x != next) { |
714 |
> |
nextItem = (E) x; |
715 |
> |
break; |
716 |
|
} |
587 |
– |
prevNode = p; |
588 |
– |
p = p.next; |
717 |
|
} |
718 |
+ |
return item; |
719 |
|
} |
720 |
|
|
721 |
|
public boolean hasNext() { |
722 |
< |
return nextNode != null; |
722 |
> |
return next != null; |
723 |
|
} |
724 |
|
|
725 |
|
public E next() { |
726 |
< |
if (nextNode == null) throw new NoSuchElementException(); |
726 |
> |
if (next == null) |
727 |
> |
throw new NoSuchElementException(); |
728 |
|
return advance(); |
729 |
|
} |
730 |
|
|
731 |
|
public void remove() { |
732 |
< |
QNode p = currentNode; |
733 |
< |
QNode prev = prevNode; |
604 |
< |
if (prev == null || p == null) |
732 |
> |
Node<E> p = curr; |
733 |
> |
if (p == null) |
734 |
|
throw new IllegalStateException(); |
735 |
|
Object x = p.get(); |
736 |
|
if (x != null && x != p && p.compareAndSet(x, p)) |
737 |
< |
clean(prev, p); |
737 |
> |
clean(pcurr, p); |
738 |
|
} |
739 |
|
} |
740 |
|
|
741 |
|
public E peek() { |
742 |
|
for (;;) { |
743 |
< |
QNode h = traversalHead(); |
744 |
< |
QNode p = h.next; |
743 |
> |
Node<E> h = traversalHead(); |
744 |
> |
Node<E> p = h.next; |
745 |
|
if (p == null) |
746 |
|
return null; |
747 |
|
Object x = p.get(); |
749 |
|
if (!p.isData) |
750 |
|
return null; |
751 |
|
if (x != null) |
752 |
< |
return (E)x; |
752 |
> |
return (E) x; |
753 |
|
} |
754 |
|
} |
755 |
|
} |
756 |
|
|
757 |
|
public boolean isEmpty() { |
758 |
|
for (;;) { |
759 |
< |
QNode h = traversalHead(); |
760 |
< |
QNode p = h.next; |
759 |
> |
Node<E> h = traversalHead(); |
760 |
> |
Node<E> p = h.next; |
761 |
|
if (p == null) |
762 |
|
return true; |
763 |
|
Object x = p.get(); |
772 |
|
|
773 |
|
public boolean hasWaitingConsumer() { |
774 |
|
for (;;) { |
775 |
< |
QNode h = traversalHead(); |
776 |
< |
QNode p = h.next; |
775 |
> |
Node<E> h = traversalHead(); |
776 |
> |
Node<E> p = h.next; |
777 |
|
if (p == null) |
778 |
|
return false; |
779 |
|
Object x = p.get(); |
784 |
|
|
785 |
|
/** |
786 |
|
* Returns the number of elements in this queue. If this queue |
787 |
< |
* contains more than <tt>Integer.MAX_VALUE</tt> elements, returns |
788 |
< |
* <tt>Integer.MAX_VALUE</tt>. |
787 |
> |
* contains more than {@code Integer.MAX_VALUE} elements, returns |
788 |
> |
* {@code Integer.MAX_VALUE}. |
789 |
|
* |
790 |
|
* <p>Beware that, unlike in most collections, this method is |
791 |
|
* <em>NOT</em> a constant-time operation. Because of the |
795 |
|
* @return the number of elements in this queue |
796 |
|
*/ |
797 |
|
public int size() { |
798 |
< |
int count = 0; |
799 |
< |
QNode h = traversalHead(); |
800 |
< |
for (QNode 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 |
|
} |
678 |
– |
return count; |
815 |
|
} |
816 |
|
|
817 |
|
public int getWaitingConsumerCount() { |
818 |
< |
int count = 0; |
819 |
< |
QNode h = traversalHead(); |
820 |
< |
for (QNode 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 |
> |
} |
836 |
> |
} |
837 |
> |
|
838 |
> |
public boolean remove(Object o) { |
839 |
> |
if (o == null) |
840 |
> |
return false; |
841 |
> |
for (;;) { |
842 |
> |
Node<E> pred = traversalHead(); |
843 |
> |
for (;;) { |
844 |
> |
Node<E> q = pred.next; |
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)) { |
852 |
+ |
clean(pred, q); |
853 |
+ |
return true; |
854 |
+ |
} |
855 |
+ |
pred = q; |
856 |
|
} |
857 |
|
} |
690 |
– |
return count; |
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 |
|
} |
871 |
|
/** |
872 |
|
* Save the state to a stream (that is, serialize it). |
873 |
|
* |
874 |
< |
* @serialData All of the elements (each an <tt>E</tt>) in |
874 |
> |
* @serialData All of the elements (each an {@code E}) in |
875 |
|
* the proper order, followed by a null |
876 |
|
* @param s the stream |
877 |
|
*/ |
878 |
|
private void writeObject(java.io.ObjectOutputStream s) |
879 |
|
throws java.io.IOException { |
880 |
|
s.defaultWriteObject(); |
881 |
< |
for (Iterator<E> it = iterator(); it.hasNext(); ) |
882 |
< |
s.writeObject(it.next()); |
881 |
> |
for (E e : this) |
882 |
> |
s.writeObject(e); |
883 |
|
// Use trailing null as sentinel |
884 |
|
s.writeObject(null); |
885 |
|
} |
887 |
|
/** |
888 |
|
* Reconstitute the Queue instance from a stream (that is, |
889 |
|
* deserialize it). |
890 |
+ |
* |
891 |
|
* @param s the stream |
892 |
|
*/ |
893 |
|
private void readObject(java.io.ObjectInputStream s) |
895 |
|
s.defaultReadObject(); |
896 |
|
resetHeadAndTail(); |
897 |
|
for (;;) { |
898 |
< |
E item = (E)s.readObject(); |
898 |
> |
@SuppressWarnings("unchecked") E item = (E) s.readObject(); |
899 |
|
if (item == null) |
900 |
|
break; |
901 |
|
else |
903 |
|
} |
904 |
|
} |
905 |
|
|
731 |
– |
|
906 |
|
// Support for resetting head/tail while deserializing |
907 |
+ |
private void resetHeadAndTail() { |
908 |
+ |
Node<E> dummy = new Node<E>(null, false); |
909 |
+ |
UNSAFE.putObjectVolatile(this, headOffset, |
910 |
+ |
new PaddedAtomicReference<Node<E>>(dummy)); |
911 |
+ |
UNSAFE.putObjectVolatile(this, tailOffset, |
912 |
+ |
new PaddedAtomicReference<Node<E>>(dummy)); |
913 |
+ |
UNSAFE.putObjectVolatile(this, cleanMeOffset, |
914 |
+ |
new PaddedAtomicReference<Node<E>>(null)); |
915 |
+ |
} |
916 |
+ |
|
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 |
< |
// Temporary Unsafe mechanics for preliminary release |
928 |
< |
private static final Unsafe _unsafe; |
929 |
< |
private static final long headOffset; |
737 |
< |
private static final long tailOffset; |
738 |
< |
private static final long cleanMeOffset; |
739 |
< |
static { |
927 |
> |
|
928 |
> |
static long objectFieldOffset(sun.misc.Unsafe UNSAFE, |
929 |
> |
String field, Class<?> klazz) { |
930 |
|
try { |
931 |
< |
if (LinkedTransferQueue.class.getClassLoader() != null) { |
932 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
933 |
< |
f.setAccessible(true); |
934 |
< |
_unsafe = (Unsafe)f.get(null); |
935 |
< |
} |
936 |
< |
else |
747 |
< |
_unsafe = Unsafe.getUnsafe(); |
748 |
< |
headOffset = _unsafe.objectFieldOffset |
749 |
< |
(LinkedTransferQueue.class.getDeclaredField("head")); |
750 |
< |
tailOffset = _unsafe.objectFieldOffset |
751 |
< |
(LinkedTransferQueue.class.getDeclaredField("tail")); |
752 |
< |
cleanMeOffset = _unsafe.objectFieldOffset |
753 |
< |
(LinkedTransferQueue.class.getDeclaredField("cleanMe")); |
754 |
< |
} catch (Exception e) { |
755 |
< |
throw new RuntimeException("Could not initialize intrinsics", e); |
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 |
< |
private void resetHeadAndTail() { |
941 |
< |
QNode dummy = new QNode(null, false); |
942 |
< |
_unsafe.putObjectVolatile(this, headOffset, |
943 |
< |
new PaddedAtomicReference<QNode>(dummy)); |
944 |
< |
_unsafe.putObjectVolatile(this, tailOffset, |
945 |
< |
new PaddedAtomicReference<QNode>(dummy)); |
946 |
< |
_unsafe.putObjectVolatile(this, cleanMeOffset, |
947 |
< |
new PaddedAtomicReference<QNode>(null)); |
948 |
< |
|
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 |
954 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
955 |
> |
public sun.misc.Unsafe run() throws Exception { |
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", |
963 |
> |
e.getCause()); |
964 |
> |
} |
965 |
> |
} |
966 |
|
} |
769 |
– |
|
967 |
|
} |