373 |
|
} |
374 |
|
|
375 |
|
final boolean casItem(Object cmp, Object val) { |
376 |
+ |
assert cmp == null || cmp.getClass() != Node.class; |
377 |
|
return UNSAFE.compareAndSwapObject(this, itemOffset, cmp, val); |
378 |
|
} |
379 |
|
|
410 |
|
*/ |
411 |
|
final boolean isMatched() { |
412 |
|
Object x = item; |
413 |
< |
return x == this || (x != null) != isData; |
413 |
> |
return (x == this) || ((x == null) == isData); |
414 |
> |
} |
415 |
> |
|
416 |
> |
/** |
417 |
> |
* Returns true if this is an unmatched request node. |
418 |
> |
*/ |
419 |
> |
final boolean isUnmatchedRequest() { |
420 |
> |
return !isData && item == null; |
421 |
|
} |
422 |
|
|
423 |
|
/** |
435 |
|
* Tries to artificially match a data node -- used by remove. |
436 |
|
*/ |
437 |
|
final boolean tryMatchData() { |
438 |
+ |
assert isData; |
439 |
|
Object x = item; |
440 |
|
if (x != null && x != this && casItem(x, null)) { |
441 |
|
LockSupport.unpark(waiter); |
457 |
|
} |
458 |
|
|
459 |
|
/** head of the queue; null until first enqueue */ |
460 |
< |
private transient volatile Node head; |
460 |
> |
transient volatile Node head; |
461 |
|
|
462 |
|
/** predecessor of dangling unspliceable node */ |
463 |
< |
private transient volatile Node cleanMe; // decl here to reduce contention |
463 |
> |
private transient volatile Node cleanMe; // decl here reduces contention |
464 |
|
|
465 |
|
/** tail of the queue; null until first append */ |
466 |
|
private transient volatile Node tail; |
487 |
|
private static final int SYNC = 2; // for transfer, take |
488 |
|
private static final int TIMEOUT = 3; // for timed poll, tryTransfer |
489 |
|
|
490 |
+ |
@SuppressWarnings("unchecked") |
491 |
+ |
static <E> E cast(Object item) { |
492 |
+ |
assert item == null || item.getClass() != Node.class; |
493 |
+ |
return (E) item; |
494 |
+ |
} |
495 |
+ |
|
496 |
|
/** |
497 |
|
* Implements all queuing methods. See above for explanation. |
498 |
|
* |
503 |
|
* @return an item if matched, else e |
504 |
|
* @throws NullPointerException if haveData mode but e is null |
505 |
|
*/ |
506 |
< |
private Object xfer(Object e, boolean haveData, int how, long nanos) { |
506 |
> |
private E xfer(E e, boolean haveData, int how, long nanos) { |
507 |
|
if (haveData && (e == null)) |
508 |
|
throw new NullPointerException(); |
509 |
|
Node s = null; // the node to append, if needed |
530 |
|
break; // unless slack < 2 |
531 |
|
} |
532 |
|
LockSupport.unpark(p.waiter); |
533 |
< |
return item; |
533 |
> |
return this.<E>cast(item); |
534 |
|
} |
535 |
|
} |
536 |
|
Node n = p.next; |
560 |
|
* predecessor |
561 |
|
*/ |
562 |
|
private Node tryAppend(Node s, boolean haveData) { |
563 |
< |
for (Node t = tail, p = t;;) { // move p to last node and append |
563 |
> |
for (Node t = tail, p = t;;) { // move p to last node and append |
564 |
|
Node n, u; // temps for reads of next & tail |
565 |
|
if (p == null && (p = head) == null) { |
566 |
|
if (casHead(null, s)) |
597 |
|
* @param nanos timeout value |
598 |
|
* @return matched item, or e if unmatched on interrupt or timeout |
599 |
|
*/ |
600 |
< |
private Object awaitMatch(Node s, Node pred, Object e, |
586 |
< |
int how, long nanos) { |
600 |
> |
private E awaitMatch(Node s, Node pred, E e, int how, long nanos) { |
601 |
|
long lastTime = (how == TIMEOUT) ? System.nanoTime() : 0L; |
602 |
|
Thread w = Thread.currentThread(); |
603 |
|
int spins = -1; // initialized after first item and cancel checks |
606 |
|
for (;;) { |
607 |
|
Object item = s.item; |
608 |
|
if (item != e) { // matched |
609 |
+ |
assert item != s; |
610 |
|
s.forgetContents(); // avoid garbage |
611 |
< |
return item; |
611 |
> |
return this.<E>cast(item); |
612 |
|
} |
613 |
|
if ((w.isInterrupted() || (how == TIMEOUT && nanos <= 0)) && |
614 |
< |
s.casItem(e, s)) { // cancel |
614 |
> |
s.casItem(e, s)) { // cancel |
615 |
|
unsplice(pred, s); |
616 |
|
return e; |
617 |
|
} |
683 |
|
/* -------------- Traversal methods -------------- */ |
684 |
|
|
685 |
|
/** |
686 |
+ |
* Returns the successor of p, or the head node if p.next has been |
687 |
+ |
* linked to self, which will only be true if traversing with a |
688 |
+ |
* stale pointer that is now off the list. |
689 |
+ |
*/ |
690 |
+ |
final Node succ(Node p) { |
691 |
+ |
Node next = p.next; |
692 |
+ |
return (p == next) ? head : next; |
693 |
+ |
} |
694 |
+ |
|
695 |
+ |
/** |
696 |
|
* Returns the first unmatched node of the given mode, or null if |
697 |
|
* none. Used by methods isEmpty, hasWaitingConsumer. |
698 |
|
*/ |
699 |
< |
private Node firstOfMode(boolean data) { |
700 |
< |
for (Node p = head; p != null; ) { |
699 |
> |
private Node firstOfMode(boolean isData) { |
700 |
> |
for (Node p = head; p != null; p = succ(p)) { |
701 |
|
if (!p.isMatched()) |
702 |
< |
return (p.isData == data) ? p : null; |
678 |
< |
Node n = p.next; |
679 |
< |
p = (n != p) ? n : head; |
702 |
> |
return (p.isData == isData) ? p : null; |
703 |
|
} |
704 |
|
return null; |
705 |
|
} |
706 |
|
|
707 |
|
/** |
708 |
|
* Returns the item in the first unmatched node with isData; or |
709 |
< |
* null if none. Used by peek. |
709 |
> |
* null if none. Used by peek. |
710 |
|
*/ |
711 |
< |
private Object firstDataItem() { |
712 |
< |
for (Node p = head; p != null; ) { |
690 |
< |
boolean isData = p.isData; |
711 |
> |
private E firstDataItem() { |
712 |
> |
for (Node p = head; p != null; p = succ(p)) { |
713 |
|
Object item = p.item; |
714 |
< |
if (item != p && (item != null) == isData) |
715 |
< |
return isData ? item : null; |
716 |
< |
Node n = p.next; |
717 |
< |
p = (n != p) ? n : head; |
714 |
> |
if (p.isData) { |
715 |
> |
if (item != null && item != p) |
716 |
> |
return this.<E>cast(item); |
717 |
> |
} |
718 |
> |
else if (item == null) |
719 |
> |
return null; |
720 |
|
} |
721 |
|
return null; |
722 |
|
} |
747 |
|
|
748 |
|
final class Itr implements Iterator<E> { |
749 |
|
private Node nextNode; // next node to return item for |
750 |
< |
private Object nextItem; // the corresponding item |
750 |
> |
private E nextItem; // the corresponding item |
751 |
|
private Node lastRet; // last returned node, to support remove |
752 |
+ |
private Node lastPred; // predecessor to unlink lastRet |
753 |
|
|
754 |
|
/** |
755 |
|
* Moves to next node after prev, or first node if prev null. |
756 |
|
*/ |
757 |
|
private void advance(Node prev) { |
758 |
+ |
lastPred = lastRet; |
759 |
|
lastRet = prev; |
760 |
< |
Node p; |
761 |
< |
if (prev == null || (p = prev.next) == prev) |
736 |
< |
p = head; |
737 |
< |
while (p != null) { |
760 |
> |
for (Node p = (prev == null) ? head : succ(prev); |
761 |
> |
p != null; p = succ(p)) { |
762 |
|
Object item = p.item; |
763 |
|
if (p.isData) { |
764 |
|
if (item != null && item != p) { |
765 |
< |
nextItem = item; |
765 |
> |
nextItem = LinkedTransferQueue.this.<E>cast(item); |
766 |
|
nextNode = p; |
767 |
|
return; |
768 |
|
} |
769 |
|
} |
770 |
|
else if (item == null) |
771 |
|
break; |
748 |
– |
Node n = p.next; |
749 |
– |
p = (n != p) ? n : head; |
772 |
|
} |
773 |
|
nextNode = null; |
774 |
|
} |
784 |
|
public final E next() { |
785 |
|
Node p = nextNode; |
786 |
|
if (p == null) throw new NoSuchElementException(); |
787 |
< |
Object e = nextItem; |
787 |
> |
E e = nextItem; |
788 |
|
advance(p); |
789 |
< |
return (E) e; |
789 |
> |
return e; |
790 |
|
} |
791 |
|
|
792 |
|
public final void remove() { |
793 |
|
Node p = lastRet; |
794 |
|
if (p == null) throw new IllegalStateException(); |
795 |
< |
lastRet = null; |
774 |
< |
findAndRemoveNode(p); |
795 |
> |
findAndRemoveDataNode(lastPred, p); |
796 |
|
} |
797 |
|
} |
798 |
|
|
826 |
|
break; |
827 |
|
} |
828 |
|
if (oldpred == pred || // Already saved |
829 |
< |
(oldpred == null && casCleanMe(null, pred))) |
830 |
< |
break; // Postpone cleaning |
829 |
> |
((oldpred == null || oldpred.next == s) && |
830 |
> |
casCleanMe(oldpred, pred))) { |
831 |
> |
break; |
832 |
> |
} |
833 |
|
} |
834 |
|
} |
835 |
|
} |
870 |
|
|
871 |
|
/** |
872 |
|
* Main implementation of Iterator.remove(). Find |
873 |
< |
* and unsplice the given node. |
873 |
> |
* and unsplice the given data node. |
874 |
> |
* @param possiblePred possible predecessor of s |
875 |
> |
* @param s the node to remove |
876 |
|
*/ |
877 |
< |
final void findAndRemoveNode(Node s) { |
877 |
> |
final void findAndRemoveDataNode(Node possiblePred, Node s) { |
878 |
> |
assert s.isData; |
879 |
|
if (s.tryMatchData()) { |
880 |
< |
Node pred = null; |
881 |
< |
Node p = head; |
882 |
< |
while (p != null) { |
883 |
< |
if (p == s) { |
884 |
< |
unsplice(pred, p); |
885 |
< |
break; |
886 |
< |
} |
887 |
< |
if (!p.isData && !p.isMatched()) |
888 |
< |
break; |
889 |
< |
pred = p; |
890 |
< |
if ((p = p.next) == pred) { // stale |
891 |
< |
pred = null; |
892 |
< |
p = head; |
880 |
> |
if (possiblePred != null && possiblePred.next == s) |
881 |
> |
unsplice(possiblePred, s); // was actual predecessor |
882 |
> |
else { |
883 |
> |
for (Node pred = null, p = head; p != null; ) { |
884 |
> |
if (p == s) { |
885 |
> |
unsplice(pred, p); |
886 |
> |
break; |
887 |
> |
} |
888 |
> |
if (p.isUnmatchedRequest()) |
889 |
> |
break; |
890 |
> |
pred = p; |
891 |
> |
if ((p = p.next) == pred) { // stale |
892 |
> |
pred = null; |
893 |
> |
p = head; |
894 |
> |
} |
895 |
|
} |
896 |
|
} |
897 |
|
} |
902 |
|
*/ |
903 |
|
private boolean findAndRemove(Object e) { |
904 |
|
if (e != null) { |
905 |
< |
Node pred = null; |
878 |
< |
Node p = head; |
879 |
< |
while (p != null) { |
905 |
> |
for (Node pred = null, p = head; p != null; ) { |
906 |
|
Object item = p.item; |
907 |
|
if (p.isData) { |
908 |
|
if (item != null && item != p && e.equals(item) && |
914 |
|
else if (item == null) |
915 |
|
break; |
916 |
|
pred = p; |
917 |
< |
if ((p = p.next) == pred) { |
917 |
> |
if ((p = p.next) == pred) { // stale |
918 |
|
pred = null; |
919 |
|
p = head; |
920 |
|
} |
1050 |
|
} |
1051 |
|
|
1052 |
|
public E take() throws InterruptedException { |
1053 |
< |
Object e = xfer(null, false, SYNC, 0); |
1053 |
> |
E e = xfer(null, false, SYNC, 0); |
1054 |
|
if (e != null) |
1055 |
< |
return (E)e; |
1055 |
> |
return e; |
1056 |
|
Thread.interrupted(); |
1057 |
|
throw new InterruptedException(); |
1058 |
|
} |
1059 |
|
|
1060 |
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
1061 |
< |
Object e = xfer(null, false, TIMEOUT, unit.toNanos(timeout)); |
1061 |
> |
E e = xfer(null, false, TIMEOUT, unit.toNanos(timeout)); |
1062 |
|
if (e != null || !Thread.interrupted()) |
1063 |
< |
return (E)e; |
1063 |
> |
return e; |
1064 |
|
throw new InterruptedException(); |
1065 |
|
} |
1066 |
|
|
1067 |
|
public E poll() { |
1068 |
< |
return (E)xfer(null, false, NOW, 0); |
1068 |
> |
return xfer(null, false, NOW, 0); |
1069 |
|
} |
1070 |
|
|
1071 |
|
/** |
1122 |
|
} |
1123 |
|
|
1124 |
|
public E peek() { |
1125 |
< |
return (E) firstDataItem(); |
1125 |
> |
return firstDataItem(); |
1126 |
|
} |
1127 |
|
|
1128 |
|
/** |
1247 |
|
* |
1248 |
|
* @return a sun.misc.Unsafe |
1249 |
|
*/ |
1250 |
< |
private static sun.misc.Unsafe getUnsafe() { |
1250 |
> |
static sun.misc.Unsafe getUnsafe() { |
1251 |
|
try { |
1252 |
|
return sun.misc.Unsafe.getUnsafe(); |
1253 |
|
} catch (SecurityException se) { |