44 |
|
* @since 1.7 |
45 |
|
* @author Doug Lea |
46 |
|
* @param <E> the type of elements held in this collection |
47 |
– |
* |
47 |
|
*/ |
48 |
|
public class LinkedTransferQueue<E> extends AbstractQueue<E> |
49 |
|
implements TransferQueue<E>, java.io.Serializable { |
80 |
|
* seems not to vary with number of CPUs (beyond 2) so is just |
81 |
|
* a constant. |
82 |
|
*/ |
83 |
< |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
83 |
> |
static final int maxTimedSpins = (NCPUS < 2) ? 0 : 32; |
84 |
|
|
85 |
|
/** |
86 |
|
* The number of times to spin before blocking in untimed waits. |
139 |
|
|
140 |
|
/** head of the queue */ |
141 |
|
private transient final PaddedAtomicReference<QNode> head; |
142 |
+ |
|
143 |
|
/** tail of the queue */ |
144 |
|
private transient final PaddedAtomicReference<QNode> tail; |
145 |
|
|
203 |
|
Object x = first.get(); |
204 |
|
if (x != first && first.compareAndSet(x, e)) { |
205 |
|
LockSupport.unpark(first.waiter); |
206 |
< |
return isData? e : x; |
206 |
> |
return isData ? e : x; |
207 |
|
} |
208 |
|
} |
209 |
|
} |
241 |
|
Object x = first.get(); |
242 |
|
if (x != first && first.compareAndSet(x, e)) { |
243 |
|
LockSupport.unpark(first.waiter); |
244 |
< |
return isData? e : x; |
244 |
> |
return isData ? e : x; |
245 |
|
} |
246 |
|
} |
247 |
|
} |
264 |
|
if (mode == NOWAIT) |
265 |
|
return null; |
266 |
|
|
267 |
< |
long lastTime = (mode == TIMEOUT)? System.nanoTime() : 0; |
267 |
> |
long lastTime = (mode == TIMEOUT) ? System.nanoTime() : 0; |
268 |
|
Thread w = Thread.currentThread(); |
269 |
|
int spins = -1; // set to desired spin count below |
270 |
|
for (;;) { |
296 |
|
if (spins < 0) { |
297 |
|
QNode h = head.get(); // only spin if at head |
298 |
|
spins = ((h != null && h.next == s) ? |
299 |
< |
(mode == TIMEOUT? |
299 |
> |
((mode == TIMEOUT) ? |
300 |
|
maxTimedSpins : maxUntimedSpins) : 0); |
301 |
|
} |
302 |
|
if (spins > 0) |
487 |
|
public E take() throws InterruptedException { |
488 |
|
Object e = xfer(null, WAIT, 0); |
489 |
|
if (e != null) |
490 |
< |
return (E)e; |
490 |
> |
return (E) e; |
491 |
|
Thread.interrupted(); |
492 |
|
throw new InterruptedException(); |
493 |
|
} |
495 |
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
496 |
|
Object e = xfer(null, TIMEOUT, unit.toNanos(timeout)); |
497 |
|
if (e != null || !Thread.interrupted()) |
498 |
< |
return (E)e; |
498 |
> |
return (E) e; |
499 |
|
throw new InterruptedException(); |
500 |
|
} |
501 |
|
|
502 |
|
public E poll() { |
503 |
< |
return (E)fulfill(null); |
503 |
> |
return (E) fulfill(null); |
504 |
|
} |
505 |
|
|
506 |
|
public int drainTo(Collection<? super E> c) { |
603 |
|
Object x = q.get(); |
604 |
|
QNode s = q.next; |
605 |
|
if (x != null && q != x && q != s) { |
606 |
< |
nextItem = (E)x; |
606 |
> |
nextItem = (E) x; |
607 |
|
snext = s; |
608 |
|
pnext = pred; |
609 |
|
next = q; |
650 |
|
if (!p.isData) |
651 |
|
return null; |
652 |
|
if (x != null) |
653 |
< |
return (E)x; |
653 |
> |
return (E) x; |
654 |
|
} |
655 |
|
} |
656 |
|
} |
765 |
|
/** |
766 |
|
* Reconstitute the Queue instance from a stream (that is, |
767 |
|
* deserialize it). |
768 |
+ |
* |
769 |
|
* @param s the stream |
770 |
|
*/ |
771 |
|
private void readObject(java.io.ObjectInputStream s) |
773 |
|
s.defaultReadObject(); |
774 |
|
resetHeadAndTail(); |
775 |
|
for (;;) { |
776 |
< |
E item = (E)s.readObject(); |
776 |
> |
E item = (E) s.readObject(); |
777 |
|
if (item == null) |
778 |
|
break; |
779 |
|
else |
785 |
|
// Support for resetting head/tail while deserializing |
786 |
|
private void resetHeadAndTail() { |
787 |
|
QNode dummy = new QNode(null, false); |
788 |
< |
_unsafe.putObjectVolatile(this, headOffset, |
788 |
> |
UNSAFE.putObjectVolatile(this, headOffset, |
789 |
|
new PaddedAtomicReference<QNode>(dummy)); |
790 |
< |
_unsafe.putObjectVolatile(this, tailOffset, |
790 |
> |
UNSAFE.putObjectVolatile(this, tailOffset, |
791 |
|
new PaddedAtomicReference<QNode>(dummy)); |
792 |
< |
_unsafe.putObjectVolatile(this, cleanMeOffset, |
792 |
> |
UNSAFE.putObjectVolatile(this, cleanMeOffset, |
793 |
|
new PaddedAtomicReference<QNode>(null)); |
794 |
|
} |
795 |
|
|
819 |
|
|
820 |
|
private static long fieldOffset(String fieldName) |
821 |
|
throws NoSuchFieldException { |
822 |
< |
return _unsafe.objectFieldOffset |
822 |
> |
return UNSAFE.objectFieldOffset |
823 |
|
(LinkedTransferQueue.class.getDeclaredField(fieldName)); |
824 |
|
} |
825 |
|
|
826 |
< |
private static final Unsafe _unsafe; |
826 |
> |
private static final Unsafe UNSAFE; |
827 |
|
private static final long headOffset; |
828 |
|
private static final long tailOffset; |
829 |
|
private static final long cleanMeOffset; |
830 |
|
static { |
831 |
|
try { |
832 |
< |
_unsafe = getUnsafe(); |
832 |
> |
UNSAFE = getUnsafe(); |
833 |
|
headOffset = fieldOffset("head"); |
834 |
|
tailOffset = fieldOffset("tail"); |
835 |
|
cleanMeOffset = fieldOffset("cleanMe"); |