10 |
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import java.util.concurrent.atomic.*; |
11 |
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import java.util.*; |
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import java.io.*; |
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+ |
import sun.misc.Unsafe; |
14 |
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import java.lang.reflect.*; |
15 |
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|
16 |
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/** |
17 |
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* An unbounded {@linkplain TransferQueue} based on linked nodes. |
21 |
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* producer. The <em>tail</em> of the queue is that element that has |
22 |
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* been on the queue the shortest time for some producer. |
23 |
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* |
24 |
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* <p>Beware that, unlike in most collections, the <tt>size</tt> |
24 |
> |
* <p>Beware that, unlike in most collections, the {@code size} |
25 |
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* method is <em>NOT</em> a constant-time operation. Because of the |
26 |
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* asynchronous nature of these queues, determining the current number |
27 |
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* of elements requires a traversal of the elements. |
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* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
42 |
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* Java Collections Framework</a>. |
43 |
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* |
44 |
< |
* @since 1.5 |
44 |
> |
* @since 1.7 |
45 |
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* @author Doug Lea |
46 |
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* @param <E> the type of elements held in this collection |
47 |
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* |
51 |
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private static final long serialVersionUID = -3223113410248163686L; |
52 |
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|
53 |
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/* |
52 |
– |
* This is still a work in prgress... |
53 |
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* |
54 |
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* This class extends the approach used in FIFO-mode |
55 |
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* SynchronousQueues. See the internal documentation, as well as |
56 |
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* the PPoPP 2006 paper "Scalable Synchronous Queues" by Scherer, |
57 |
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* Lea & Scott |
58 |
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* (http://www.cs.rice.edu/~wns1/papers/2006-PPoPP-SQ.pdf) |
59 |
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* |
60 |
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* The main extension is to provide different Wait modes |
61 |
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* for the main "xfer" method that puts or takes items. |
62 |
< |
* These don't impact the basic dual-queue logic, but instead |
63 |
< |
* control whether or how threads block upon insertion |
64 |
< |
* of request or data nodes into the dual queue. |
60 |
> |
* The main extension is to provide different Wait modes for the |
61 |
> |
* main "xfer" method that puts or takes items. These don't |
62 |
> |
* impact the basic dual-queue logic, but instead control whether |
63 |
> |
* or how threads block upon insertion of request or data nodes |
64 |
> |
* into the dual queue. It also uses slightly different |
65 |
> |
* conventions for tracking whether nodes are off-list or |
66 |
> |
* cancelled. |
67 |
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*/ |
68 |
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|
69 |
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// Wait modes for xfer method |
81 |
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* seems not to vary with number of CPUs (beyond 2) so is just |
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* a constant. |
83 |
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*/ |
84 |
< |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
84 |
> |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
85 |
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|
86 |
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/** |
87 |
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* The number of times to spin before blocking in untimed waits. |
96 |
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*/ |
97 |
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static final long spinForTimeoutThreshold = 1000L; |
98 |
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|
99 |
< |
/** |
100 |
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* Node class for LinkedTransferQueue. Opportunistically subclasses from |
101 |
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* AtomicReference to represent item. Uses Object, not E, to allow |
102 |
< |
* setting item to "this" after use, to avoid garbage |
103 |
< |
* retention. Similarly, setting the next field to this is used as |
104 |
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* sentinel that node is off list. |
99 |
> |
/** |
100 |
> |
* Node class for LinkedTransferQueue. Opportunistically |
101 |
> |
* subclasses from AtomicReference to represent item. Uses Object, |
102 |
> |
* not E, to allow setting item to "this" after use, to avoid |
103 |
> |
* garbage retention. Similarly, setting the next field to this is |
104 |
> |
* used as sentinel that node is off list. |
105 |
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*/ |
106 |
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static final class QNode extends AtomicReference<Object> { |
107 |
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volatile QNode next; |
133 |
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} |
134 |
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|
135 |
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|
136 |
< |
private final QNode dummy = new QNode(null, false); |
137 |
< |
private final PaddedAtomicReference<QNode> head = |
138 |
< |
new PaddedAtomicReference<QNode>(dummy); |
139 |
< |
private final PaddedAtomicReference<QNode> tail = |
138 |
< |
new PaddedAtomicReference<QNode>(dummy); |
136 |
> |
/** head of the queue */ |
137 |
> |
private transient final PaddedAtomicReference<QNode> head; |
138 |
> |
/** tail of the queue */ |
139 |
> |
private transient final PaddedAtomicReference<QNode> tail; |
140 |
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|
141 |
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/** |
142 |
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* Reference to a cancelled node that might not yet have been |
143 |
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* unlinked from queue because it was the last inserted node |
144 |
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* when it cancelled. |
145 |
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*/ |
146 |
< |
private final PaddedAtomicReference<QNode> cleanMe = |
146 |
< |
new PaddedAtomicReference<QNode>(null); |
146 |
> |
private transient final PaddedAtomicReference<QNode> cleanMe; |
147 |
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|
148 |
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/** |
149 |
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* Tries to cas nh as new head; if successful, unlink |
156 |
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} |
157 |
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return false; |
158 |
|
} |
159 |
< |
|
159 |
> |
|
160 |
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/** |
161 |
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* Puts or takes an item. Used for most queue operations (except |
162 |
< |
* poll() and tryTransfer()) |
163 |
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* @param e the item or if null, signfies that this is a take |
162 |
> |
* poll() and tryTransfer()). See the similar code in |
163 |
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* SynchronousQueue for detailed explanation. |
164 |
> |
* @param e the item or if null, signifies that this is a take |
165 |
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* @param mode the wait mode: NOWAIT, TIMEOUT, WAIT |
166 |
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* @param nanos timeout in nanosecs, used only if mode is TIMEOUT |
167 |
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* @return an item, or null on failure |
189 |
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return awaitFulfill(t, s, e, mode, nanos); |
190 |
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} |
191 |
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} |
192 |
< |
|
192 |
> |
|
193 |
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else if (h != null) { |
194 |
|
QNode first = h.next; |
195 |
< |
if (t == tail.get() && first != null && |
195 |
> |
if (t == tail.get() && first != null && |
196 |
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advanceHead(h, first)) { |
197 |
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Object x = first.get(); |
198 |
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if (x != first && first.compareAndSet(x, e)) { |
207 |
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|
208 |
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/** |
209 |
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* Version of xfer for poll() and tryTransfer, which |
210 |
< |
* simpifies control paths both here and in xfer |
210 |
> |
* simplifies control paths both here and in xfer |
211 |
|
*/ |
212 |
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private Object fulfill(Object e) { |
213 |
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boolean isData = (e != null); |
229 |
|
} |
230 |
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else if (h != null) { |
231 |
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QNode first = h.next; |
232 |
< |
if (t == tail.get() && |
232 |
> |
if (t == tail.get() && |
233 |
|
first != null && |
234 |
|
advanceHead(h, first)) { |
235 |
|
Object x = first.get(); |
253 |
|
* @param nanos timeout value |
254 |
|
* @return matched item, or s if cancelled |
255 |
|
*/ |
256 |
< |
private Object awaitFulfill(QNode pred, QNode s, Object e, |
256 |
> |
private Object awaitFulfill(QNode pred, QNode s, Object e, |
257 |
|
int mode, long nanos) { |
258 |
|
if (mode == NOWAIT) |
259 |
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return null; |
267 |
|
Object x = s.get(); |
268 |
|
if (x != e) { // Node was matched or cancelled |
269 |
|
advanceHead(pred, s); // unlink if head |
270 |
< |
if (x == s) // was cancelled |
271 |
< |
return clean(pred, s); |
272 |
< |
else if (x != null) { |
270 |
> |
if (x == s) { // was cancelled |
271 |
> |
clean(pred, s); |
272 |
> |
return null; |
273 |
> |
} |
274 |
> |
else if (x != null) { |
275 |
|
s.set(s); // avoid garbage retention |
276 |
|
return x; |
277 |
|
} |
278 |
|
else |
279 |
|
return e; |
280 |
|
} |
278 |
– |
|
281 |
|
if (mode == TIMEOUT) { |
282 |
|
long now = System.nanoTime(); |
283 |
|
nanos -= now - lastTime; |
290 |
|
if (spins < 0) { |
291 |
|
QNode h = head.get(); // only spin if at head |
292 |
|
spins = ((h != null && h.next == s) ? |
293 |
< |
(mode == TIMEOUT? |
293 |
> |
(mode == TIMEOUT? |
294 |
|
maxTimedSpins : maxUntimedSpins) : 0); |
295 |
|
} |
296 |
|
if (spins > 0) |
298 |
|
else if (s.waiter == null) |
299 |
|
s.waiter = w; |
300 |
|
else if (mode != TIMEOUT) { |
301 |
< |
// LockSupport.park(this); |
300 |
< |
LockSupport.park(); // allows run on java5 |
301 |
> |
LockSupport.park(this); |
302 |
|
s.waiter = null; |
303 |
|
spins = -1; |
304 |
|
} |
305 |
|
else if (nanos > spinForTimeoutThreshold) { |
306 |
< |
// LockSupport.parkNanos(this, nanos); |
306 |
< |
LockSupport.parkNanos(nanos); |
306 |
> |
LockSupport.parkNanos(this, nanos); |
307 |
|
s.waiter = null; |
308 |
|
spins = -1; |
309 |
|
} |
311 |
|
} |
312 |
|
|
313 |
|
/** |
314 |
+ |
* Returns validated tail for use in cleaning methods |
315 |
+ |
*/ |
316 |
+ |
private QNode getValidatedTail() { |
317 |
+ |
for (;;) { |
318 |
+ |
QNode h = head.get(); |
319 |
+ |
QNode first = h.next; |
320 |
+ |
if (first != null && first.next == first) { // help advance |
321 |
+ |
advanceHead(h, first); |
322 |
+ |
continue; |
323 |
+ |
} |
324 |
+ |
QNode t = tail.get(); |
325 |
+ |
QNode last = t.next; |
326 |
+ |
if (t == tail.get()) { |
327 |
+ |
if (last != null) |
328 |
+ |
tail.compareAndSet(t, last); // help advance |
329 |
+ |
else |
330 |
+ |
return t; |
331 |
+ |
} |
332 |
+ |
} |
333 |
+ |
} |
334 |
+ |
|
335 |
+ |
/** |
336 |
|
* Gets rid of cancelled node s with original predecessor pred. |
337 |
< |
* @return null (to simplify use by callers) |
337 |
> |
* @param pred predecessor of cancelled node |
338 |
> |
* @param s the cancelled node |
339 |
|
*/ |
340 |
< |
private Object clean(QNode pred, QNode s) { |
340 |
> |
private void clean(QNode pred, QNode s) { |
341 |
|
Thread w = s.waiter; |
342 |
|
if (w != null) { // Wake up thread |
343 |
|
s.waiter = null; |
344 |
|
if (w != Thread.currentThread()) |
345 |
|
LockSupport.unpark(w); |
346 |
|
} |
347 |
< |
|
348 |
< |
for (;;) { |
349 |
< |
if (pred.next != s) // already cleaned |
350 |
< |
return null; |
351 |
< |
QNode h = head.get(); |
352 |
< |
QNode hn = h.next; // Absorb cancelled first node as head |
353 |
< |
if (hn != null && hn.next == hn) { |
354 |
< |
advanceHead(h, hn); |
355 |
< |
continue; |
356 |
< |
} |
357 |
< |
QNode t = tail.get(); // Ensure consistent read for tail |
358 |
< |
if (t == h) |
359 |
< |
return null; |
337 |
< |
QNode tn = t.next; |
338 |
< |
if (t != tail.get()) |
339 |
< |
continue; |
340 |
< |
if (tn != null) { // Help advance tail |
341 |
< |
tail.compareAndSet(t, tn); |
342 |
< |
continue; |
343 |
< |
} |
344 |
< |
if (s != t) { // If not tail, try to unsplice |
345 |
< |
QNode sn = s.next; |
347 |
> |
/* |
348 |
> |
* At any given time, exactly one node on list cannot be |
349 |
> |
* deleted -- the last inserted node. To accommodate this, if |
350 |
> |
* we cannot delete s, we save its predecessor as "cleanMe", |
351 |
> |
* processing the previously saved version first. At least one |
352 |
> |
* of node s or the node previously saved can always be |
353 |
> |
* processed, so this always terminates. |
354 |
> |
*/ |
355 |
> |
while (pred.next == s) { |
356 |
> |
QNode oldpred = reclean(); // First, help get rid of cleanMe |
357 |
> |
QNode t = getValidatedTail(); |
358 |
> |
if (s != t) { // If not tail, try to unsplice |
359 |
> |
QNode sn = s.next; // s.next == s means s already off list |
360 |
|
if (sn == s || pred.casNext(s, sn)) |
361 |
< |
return null; |
361 |
> |
break; |
362 |
|
} |
363 |
< |
QNode dp = cleanMe.get(); |
364 |
< |
if (dp != null) { // Try unlinking previous cancelled node |
365 |
< |
QNode d = dp.next; |
366 |
< |
QNode dn; |
367 |
< |
if (d == null || // d is gone or |
368 |
< |
d == dp || // d is off list or |
369 |
< |
d.get() != d || // d not cancelled or |
370 |
< |
(d != t && // d not tail and |
371 |
< |
(dn = d.next) != null && // has successor |
372 |
< |
dn != d && // that is on list |
373 |
< |
dp.casNext(d, dn))) // d unspliced |
374 |
< |
cleanMe.compareAndSet(dp, null); |
375 |
< |
if (dp == pred) |
376 |
< |
return null; // s is already saved node |
377 |
< |
} |
378 |
< |
else if (cleanMe.compareAndSet(null, pred)) |
379 |
< |
return null; // Postpone cleaning s |
363 |
> |
else if (oldpred == pred || // Already saved |
364 |
> |
(oldpred == null && cleanMe.compareAndSet(null, pred))) |
365 |
> |
break; // Postpone cleaning |
366 |
> |
} |
367 |
> |
} |
368 |
> |
|
369 |
> |
/** |
370 |
> |
* Tries to unsplice the cancelled node held in cleanMe that was |
371 |
> |
* previously uncleanable because it was at tail. |
372 |
> |
* @return current cleanMe node (or null) |
373 |
> |
*/ |
374 |
> |
private QNode reclean() { |
375 |
> |
/* |
376 |
> |
* cleanMe is, or at one time was, predecessor of cancelled |
377 |
> |
* node s that was the tail so could not be unspliced. If s |
378 |
> |
* is no longer the tail, try to unsplice if necessary and |
379 |
> |
* make cleanMe slot available. This differs from similar |
380 |
> |
* code in clean() because we must check that pred still |
381 |
> |
* points to a cancelled node that must be unspliced -- if |
382 |
> |
* not, we can (must) clear cleanMe without unsplicing. |
383 |
> |
* This can loop only due to contention on casNext or |
384 |
> |
* clearing cleanMe. |
385 |
> |
*/ |
386 |
> |
QNode pred; |
387 |
> |
while ((pred = cleanMe.get()) != null) { |
388 |
> |
QNode t = getValidatedTail(); |
389 |
> |
QNode s = pred.next; |
390 |
> |
if (s != t) { |
391 |
> |
QNode sn; |
392 |
> |
if (s == null || s == pred || s.get() != s || |
393 |
> |
(sn = s.next) == s || pred.casNext(s, sn)) |
394 |
> |
cleanMe.compareAndSet(pred, null); |
395 |
> |
} |
396 |
> |
else // s is still tail; cannot clean |
397 |
> |
break; |
398 |
|
} |
399 |
+ |
return pred; |
400 |
|
} |
401 |
< |
|
401 |
> |
|
402 |
|
/** |
403 |
< |
* Creates an initially empty <tt>LinkedTransferQueue</tt>. |
403 |
> |
* Creates an initially empty {@code LinkedTransferQueue}. |
404 |
|
*/ |
405 |
|
public LinkedTransferQueue() { |
406 |
+ |
QNode dummy = new QNode(null, false); |
407 |
+ |
head = new PaddedAtomicReference<QNode>(dummy); |
408 |
+ |
tail = new PaddedAtomicReference<QNode>(dummy); |
409 |
+ |
cleanMe = new PaddedAtomicReference<QNode>(null); |
410 |
|
} |
411 |
|
|
412 |
|
/** |
413 |
< |
* Creates a <tt>LinkedTransferQueue</tt> |
413 |
> |
* Creates a {@code LinkedTransferQueue} |
414 |
|
* initially containing the elements of the given collection, |
415 |
|
* added in traversal order of the collection's iterator. |
416 |
|
* @param c the collection of elements to initially contain |
418 |
|
* of its elements are null |
419 |
|
*/ |
420 |
|
public LinkedTransferQueue(Collection<? extends E> c) { |
421 |
+ |
this(); |
422 |
|
addAll(c); |
423 |
|
} |
424 |
|
|
428 |
|
xfer(e, NOWAIT, 0); |
429 |
|
} |
430 |
|
|
431 |
< |
public boolean offer(E e, long timeout, TimeUnit unit) |
431 |
> |
public boolean offer(E e, long timeout, TimeUnit unit) |
432 |
|
throws InterruptedException { |
433 |
|
if (e == null) throw new NullPointerException(); |
434 |
|
if (Thread.interrupted()) throw new InterruptedException(); |
445 |
|
public void transfer(E e) throws InterruptedException { |
446 |
|
if (e == null) throw new NullPointerException(); |
447 |
|
if (xfer(e, WAIT, 0) == null) { |
448 |
< |
Thread.interrupted(); |
448 |
> |
Thread.interrupted(); |
449 |
|
throw new InterruptedException(); |
450 |
< |
} |
450 |
> |
} |
451 |
|
} |
452 |
|
|
453 |
|
public boolean tryTransfer(E e, long timeout, TimeUnit unit) |
469 |
|
Object e = xfer(null, WAIT, 0); |
470 |
|
if (e != null) |
471 |
|
return (E)e; |
472 |
< |
Thread.interrupted(); |
472 |
> |
Thread.interrupted(); |
473 |
|
throw new InterruptedException(); |
474 |
|
} |
475 |
|
|
525 |
|
QNode last = t.next; |
526 |
|
QNode first = h.next; |
527 |
|
if (t == tail.get()) { |
528 |
< |
if (last != null) |
528 |
> |
if (last != null) |
529 |
|
tail.compareAndSet(t, last); |
530 |
|
else if (first != null) { |
531 |
|
Object x = first.get(); |
532 |
< |
if (x == first) |
533 |
< |
advanceHead(h, first); |
532 |
> |
if (x == first) |
533 |
> |
advanceHead(h, first); |
534 |
|
else |
535 |
|
return h; |
536 |
|
} |
547 |
|
} |
548 |
|
|
549 |
|
/** |
550 |
< |
* Iterators. Basic strategy os to travers list, treating |
550 |
> |
* Iterators. Basic strategy is to traverse list, treating |
551 |
|
* non-data (i.e., request) nodes as terminating list. |
552 |
|
* Once a valid data node is found, the item is cached |
553 |
|
* so that the next call to next() will return it even |
558 |
|
QNode currentNode; // last returned node, for remove() |
559 |
|
QNode prevNode; // predecessor of last returned node |
560 |
|
E nextItem; // Cache of next item, once commited to in next |
561 |
< |
|
561 |
> |
|
562 |
|
Itr() { |
563 |
|
nextNode = traversalHead(); |
564 |
|
advance(); |
565 |
|
} |
566 |
< |
|
566 |
> |
|
567 |
|
E advance() { |
568 |
|
prevNode = currentNode; |
569 |
|
currentNode = nextNode; |
570 |
|
E x = nextItem; |
571 |
< |
|
571 |
> |
|
572 |
|
QNode p = nextNode.next; |
573 |
|
for (;;) { |
574 |
|
if (p == null || !p.isData) { |
581 |
|
nextNode = p; |
582 |
|
nextItem = (E)item; |
583 |
|
return x; |
584 |
< |
} |
584 |
> |
} |
585 |
|
prevNode = p; |
586 |
|
p = p.next; |
587 |
|
} |
588 |
|
} |
589 |
< |
|
589 |
> |
|
590 |
|
public boolean hasNext() { |
591 |
|
return nextNode != null; |
592 |
|
} |
593 |
< |
|
593 |
> |
|
594 |
|
public E next() { |
595 |
|
if (nextNode == null) throw new NoSuchElementException(); |
596 |
|
return advance(); |
597 |
|
} |
598 |
< |
|
598 |
> |
|
599 |
|
public void remove() { |
600 |
|
QNode p = currentNode; |
601 |
|
QNode prev = prevNode; |
602 |
< |
if (prev == null || p == null) |
602 |
> |
if (prev == null || p == null) |
603 |
|
throw new IllegalStateException(); |
604 |
|
Object x = p.get(); |
605 |
|
if (x != null && x != p && p.compareAndSet(x, p)) |
646 |
|
if (p == null) |
647 |
|
return false; |
648 |
|
Object x = p.get(); |
649 |
< |
if (p != x) |
649 |
> |
if (p != x) |
650 |
|
return !p.isData; |
651 |
|
} |
652 |
|
} |
653 |
< |
|
653 |
> |
|
654 |
|
/** |
655 |
|
* Returns the number of elements in this queue. If this queue |
656 |
< |
* contains more than <tt>Integer.MAX_VALUE</tt> elements, returns |
657 |
< |
* <tt>Integer.MAX_VALUE</tt>. |
656 |
> |
* contains more than {@code Integer.MAX_VALUE} elements, returns |
657 |
> |
* {@code Integer.MAX_VALUE}. |
658 |
|
* |
659 |
|
* <p>Beware that, unlike in most collections, this method is |
660 |
|
* <em>NOT</em> a constant-time operation. Because of the |
668 |
|
QNode h = traversalHead(); |
669 |
|
for (QNode p = h.next; p != null && p.isData; p = p.next) { |
670 |
|
Object x = p.get(); |
671 |
< |
if (x != null && x != p) { |
671 |
> |
if (x != null && x != p) { |
672 |
|
if (++count == Integer.MAX_VALUE) // saturated |
673 |
|
break; |
674 |
|
} |
695 |
|
/** |
696 |
|
* Save the state to a stream (that is, serialize it). |
697 |
|
* |
698 |
< |
* @serialData All of the elements (each an <tt>E</tt>) in |
698 |
> |
* @serialData All of the elements (each an {@code E}) in |
699 |
|
* the proper order, followed by a null |
700 |
|
* @param s the stream |
701 |
|
*/ |
716 |
|
private void readObject(java.io.ObjectInputStream s) |
717 |
|
throws java.io.IOException, ClassNotFoundException { |
718 |
|
s.defaultReadObject(); |
719 |
+ |
resetHeadAndTail(); |
720 |
|
for (;;) { |
721 |
|
E item = (E)s.readObject(); |
722 |
|
if (item == null) |
725 |
|
offer(item); |
726 |
|
} |
727 |
|
} |
728 |
+ |
|
729 |
+ |
|
730 |
+ |
// Support for resetting head/tail while deserializing |
731 |
+ |
private void resetHeadAndTail() { |
732 |
+ |
QNode dummy = new QNode(null, false); |
733 |
+ |
_unsafe.putObjectVolatile(this, headOffset, |
734 |
+ |
new PaddedAtomicReference<QNode>(dummy)); |
735 |
+ |
_unsafe.putObjectVolatile(this, tailOffset, |
736 |
+ |
new PaddedAtomicReference<QNode>(dummy)); |
737 |
+ |
_unsafe.putObjectVolatile(this, cleanMeOffset, |
738 |
+ |
new PaddedAtomicReference<QNode>(null)); |
739 |
+ |
} |
740 |
+ |
|
741 |
+ |
// Temporary Unsafe mechanics for preliminary release |
742 |
+ |
private static Unsafe getUnsafe() throws Throwable { |
743 |
+ |
try { |
744 |
+ |
return Unsafe.getUnsafe(); |
745 |
+ |
} catch (SecurityException se) { |
746 |
+ |
try { |
747 |
+ |
return java.security.AccessController.doPrivileged |
748 |
+ |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
749 |
+ |
public Unsafe run() throws Exception { |
750 |
+ |
return getUnsafePrivileged(); |
751 |
+ |
}}); |
752 |
+ |
} catch (java.security.PrivilegedActionException e) { |
753 |
+ |
throw e.getCause(); |
754 |
+ |
} |
755 |
+ |
} |
756 |
+ |
} |
757 |
+ |
|
758 |
+ |
private static Unsafe getUnsafePrivileged() |
759 |
+ |
throws NoSuchFieldException, IllegalAccessException { |
760 |
+ |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
761 |
+ |
f.setAccessible(true); |
762 |
+ |
return (Unsafe)f.get(null); |
763 |
+ |
} |
764 |
+ |
|
765 |
+ |
private static long fieldOffset(String fieldName) |
766 |
+ |
throws NoSuchFieldException { |
767 |
+ |
return _unsafe.objectFieldOffset |
768 |
+ |
(LinkedTransferQueue.class.getDeclaredField(fieldName)); |
769 |
+ |
} |
770 |
+ |
|
771 |
+ |
private static final Unsafe _unsafe; |
772 |
+ |
private static final long headOffset; |
773 |
+ |
private static final long tailOffset; |
774 |
+ |
private static final long cleanMeOffset; |
775 |
+ |
static { |
776 |
+ |
try { |
777 |
+ |
_unsafe = getUnsafe(); |
778 |
+ |
headOffset = fieldOffset("head"); |
779 |
+ |
tailOffset = fieldOffset("tail"); |
780 |
+ |
cleanMeOffset = fieldOffset("cleanMe"); |
781 |
+ |
} catch (Throwable e) { |
782 |
+ |
throw new RuntimeException("Could not initialize intrinsics", e); |
783 |
+ |
} |
784 |
+ |
} |
785 |
+ |
|
786 |
|
} |