479 |
|
} |
480 |
|
|
481 |
|
/* |
482 |
< |
* Possible values for "how" argument in xfer method. Beware that |
483 |
< |
* the order of assigned numerical values matters. |
482 |
> |
* Possible values for "how" argument in xfer method. |
483 |
|
*/ |
484 |
< |
private static final int NOW = 0; // for untimed poll, tryTransfer |
485 |
< |
private static final int ASYNC = 1; // for offer, put, add |
486 |
< |
private static final int SYNC = 2; // for transfer, take |
487 |
< |
private static final int TIMEOUT = 3; // for timed poll, tryTransfer |
484 |
> |
private static final int NOW = 0; // for untimed poll, tryTransfer |
485 |
> |
private static final int ASYNC = 1; // for offer, put, add |
486 |
> |
private static final int SYNC = 2; // for transfer, take |
487 |
> |
private static final int TIMED = 3; // for timed poll, tryTransfer |
488 |
|
|
489 |
|
@SuppressWarnings("unchecked") |
490 |
|
static <E> E cast(Object item) { |
497 |
|
* |
498 |
|
* @param e the item or null for take |
499 |
|
* @param haveData true if this is a put, else a take |
500 |
< |
* @param how NOW, ASYNC, SYNC, or TIMEOUT |
501 |
< |
* @param nanos timeout in nanosecs, used only if mode is TIMEOUT |
500 |
> |
* @param how NOW, ASYNC, SYNC, or TIMED |
501 |
> |
* @param nanos timeout in nanosecs, used only if mode is TIMED |
502 |
|
* @return an item if matched, else e |
503 |
|
* @throws NullPointerException if haveData mode but e is null |
504 |
|
*/ |
536 |
|
p = (p != n) ? n : (h = head); // Use head if p offlist |
537 |
|
} |
538 |
|
|
539 |
< |
if (how >= ASYNC) { // No matches available |
539 |
> |
if (how != NOW) { // No matches available |
540 |
|
if (s == null) |
541 |
|
s = new Node(e, haveData); |
542 |
|
Node pred = tryAppend(s, haveData); |
543 |
|
if (pred == null) |
544 |
|
continue retry; // lost race vs opposite mode |
545 |
< |
if (how >= SYNC) |
546 |
< |
return awaitMatch(s, pred, e, how, nanos); |
545 |
> |
if (how != ASYNC) |
546 |
> |
return awaitMatch(s, pred, e, (how == TIMED), nanos); |
547 |
|
} |
548 |
|
return e; // not waiting |
549 |
|
} |
592 |
|
* predecessor, or null if unknown (the null case does not occur |
593 |
|
* in any current calls but may in possible future extensions) |
594 |
|
* @param e the comparison value for checking match |
595 |
< |
* @param how either SYNC or TIMEOUT |
596 |
< |
* @param nanos timeout value |
595 |
> |
* @param timed if true, wait only until timeout elapses |
596 |
> |
* @param nanos timeout in nanosecs, used only if timed is true |
597 |
|
* @return matched item, or e if unmatched on interrupt or timeout |
598 |
|
*/ |
599 |
< |
private E awaitMatch(Node s, Node pred, E e, int how, long nanos) { |
600 |
< |
long lastTime = (how == TIMEOUT) ? System.nanoTime() : 0L; |
599 |
> |
private E awaitMatch(Node s, Node pred, E e, boolean timed, long nanos) { |
600 |
> |
long lastTime = timed ? System.nanoTime() : 0L; |
601 |
|
Thread w = Thread.currentThread(); |
602 |
|
int spins = -1; // initialized after first item and cancel checks |
603 |
|
ThreadLocalRandom randomYields = null; // bound if needed |
609 |
|
s.forgetContents(); // avoid garbage |
610 |
|
return this.<E>cast(item); |
611 |
|
} |
612 |
< |
if ((w.isInterrupted() || (how == TIMEOUT && nanos <= 0)) && |
612 |
> |
if ((w.isInterrupted() || (timed && nanos <= 0)) && |
613 |
|
s.casItem(e, s)) { // cancel |
614 |
|
unsplice(pred, s); |
615 |
|
return e; |
628 |
|
else if (s.waiter == null) { |
629 |
|
s.waiter = w; // request unpark then recheck |
630 |
|
} |
631 |
< |
else if (how == TIMEOUT) { |
631 |
> |
else if (timed) { |
632 |
|
long now = System.nanoTime(); |
633 |
|
if ((nanos -= now - lastTime) > 0) |
634 |
|
LockSupport.parkNanos(this, nanos); |
682 |
|
/* -------------- Traversal methods -------------- */ |
683 |
|
|
684 |
|
/** |
685 |
+ |
* Returns the successor of p, or the head node if p.next has been |
686 |
+ |
* linked to self, which will only be true if traversing with a |
687 |
+ |
* stale pointer that is now off the list. |
688 |
+ |
*/ |
689 |
+ |
final Node succ(Node p) { |
690 |
+ |
Node next = p.next; |
691 |
+ |
return (p == next) ? head : next; |
692 |
+ |
} |
693 |
+ |
|
694 |
+ |
/** |
695 |
|
* Returns the first unmatched node of the given mode, or null if |
696 |
|
* none. Used by methods isEmpty, hasWaitingConsumer. |
697 |
|
*/ |
698 |
< |
private Node firstOfMode(boolean data) { |
699 |
< |
for (Node p = head; p != null; ) { |
698 |
> |
private Node firstOfMode(boolean isData) { |
699 |
> |
for (Node p = head; p != null; p = succ(p)) { |
700 |
|
if (!p.isMatched()) |
701 |
< |
return (p.isData == data) ? p : null; |
693 |
< |
Node n = p.next; |
694 |
< |
p = (n != p) ? n : head; |
701 |
> |
return (p.isData == isData) ? p : null; |
702 |
|
} |
703 |
|
return null; |
704 |
|
} |
708 |
|
* null if none. Used by peek. |
709 |
|
*/ |
710 |
|
private E firstDataItem() { |
711 |
< |
for (Node p = head; p != null; ) { |
705 |
< |
boolean isData = p.isData; |
711 |
> |
for (Node p = head; p != null; p = succ(p)) { |
712 |
|
Object item = p.item; |
713 |
< |
if (item != p && (item != null) == isData) |
714 |
< |
return isData ? this.<E>cast(item) : null; |
715 |
< |
Node n = p.next; |
716 |
< |
p = (n != p) ? n : head; |
713 |
> |
if (p.isData) { |
714 |
> |
if (item != null && item != p) |
715 |
> |
return this.<E>cast(item); |
716 |
> |
} |
717 |
> |
else if (item == null) |
718 |
> |
return null; |
719 |
|
} |
720 |
|
return null; |
721 |
|
} |
756 |
|
private void advance(Node prev) { |
757 |
|
lastPred = lastRet; |
758 |
|
lastRet = prev; |
759 |
< |
Node p; |
760 |
< |
if (prev == null || (p = prev.next) == prev) |
753 |
< |
p = head; |
754 |
< |
while (p != null) { |
759 |
> |
for (Node p = (prev == null) ? head : succ(prev); |
760 |
> |
p != null; p = succ(p)) { |
761 |
|
Object item = p.item; |
762 |
|
if (p.isData) { |
763 |
|
if (item != null && item != p) { |
768 |
|
} |
769 |
|
else if (item == null) |
770 |
|
break; |
765 |
– |
Node n = p.next; |
766 |
– |
p = (n != p) ? n : head; |
771 |
|
} |
772 |
|
nextNode = null; |
773 |
|
} |
868 |
|
} |
869 |
|
|
870 |
|
/** |
871 |
< |
* Main implementation of Iterator.remove(). Find |
872 |
< |
* and unsplice the given data node. |
871 |
> |
* Main implementation of Iterator.remove(). Finds |
872 |
> |
* and unsplices the given data node. |
873 |
> |
* |
874 |
|
* @param possiblePred possible predecessor of s |
875 |
|
* @param s the node to remove |
876 |
|
*/ |
1042 |
|
*/ |
1043 |
|
public boolean tryTransfer(E e, long timeout, TimeUnit unit) |
1044 |
|
throws InterruptedException { |
1045 |
< |
if (xfer(e, true, TIMEOUT, unit.toNanos(timeout)) == null) |
1045 |
> |
if (xfer(e, true, TIMED, unit.toNanos(timeout)) == null) |
1046 |
|
return true; |
1047 |
|
if (!Thread.interrupted()) |
1048 |
|
return false; |
1058 |
|
} |
1059 |
|
|
1060 |
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
1061 |
< |
E e = xfer(null, false, TIMEOUT, unit.toNanos(timeout)); |
1061 |
> |
E e = xfer(null, false, TIMED, unit.toNanos(timeout)); |
1062 |
|
if (e != null || !Thread.interrupted()) |
1063 |
|
return e; |
1064 |
|
throw new InterruptedException(); |