| 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; |
| 479 |
|
} |
| 480 |
|
|
| 481 |
|
/* |
| 482 |
< |
* Possible values for "how" argument in xfer method. Beware that |
| 474 |
< |
* 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) { |
| 491 |
> |
assert item == null || item.getClass() != Node.class; |
| 492 |
> |
return (E) item; |
| 493 |
> |
} |
| 494 |
|
|
| 495 |
|
/** |
| 496 |
|
* Implements all queuing methods. See above for explanation. |
| 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 |
|
*/ |
| 505 |
< |
private Object xfer(Object e, boolean haveData, int how, long nanos) { |
| 505 |
> |
private E xfer(E e, boolean haveData, int how, long nanos) { |
| 506 |
|
if (haveData && (e == null)) |
| 507 |
|
throw new NullPointerException(); |
| 508 |
|
Node s = null; // the node to append, if needed |
| 516 |
|
if (isData == haveData) // can't match |
| 517 |
|
break; |
| 518 |
|
if (p.casItem(item, e)) { // match |
| 519 |
< |
LockSupport.unpark(p.waiter); |
| 520 |
< |
while (p != h) { // update head |
| 521 |
< |
Node n = p.next; // by 2 unless singleton |
| 522 |
< |
if (n != null) |
| 523 |
< |
p = n; |
| 510 |
< |
if (head == h && casHead(h, p)) { |
| 519 |
> |
for (Node q = p; q != h;) { |
| 520 |
> |
Node n = q.next; // update head by 2 |
| 521 |
> |
if (n != null) // unless singleton |
| 522 |
> |
q = n; |
| 523 |
> |
if (head == h && casHead(h, q)) { |
| 524 |
|
h.forgetNext(); |
| 525 |
|
break; |
| 526 |
|
} // advance and retry |
| 527 |
|
if ((h = head) == null || |
| 528 |
< |
(p = h.next) == null || !p.isMatched()) |
| 528 |
> |
(q = h.next) == null || !q.isMatched()) |
| 529 |
|
break; // unless slack < 2 |
| 530 |
|
} |
| 531 |
< |
return item; |
| 531 |
> |
LockSupport.unpark(p.waiter); |
| 532 |
> |
return this.<E>cast(item); |
| 533 |
|
} |
| 534 |
|
} |
| 535 |
|
Node n = p.next; |
| 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 |
|
} |
| 559 |
|
* predecessor |
| 560 |
|
*/ |
| 561 |
|
private Node tryAppend(Node s, boolean haveData) { |
| 562 |
< |
for (Node t = tail, p = t;;) { // move p to last node and append |
| 562 |
> |
for (Node t = tail, p = t;;) { // move p to last node and append |
| 563 |
|
Node n, u; // temps for reads of next & tail |
| 564 |
|
if (p == null && (p = head) == null) { |
| 565 |
|
if (casHead(null, s)) |
| 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 Object awaitMatch(Node s, Node pred, Object e, |
| 600 |
< |
int how, long nanos) { |
| 587 |
< |
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 |
| 605 |
|
for (;;) { |
| 606 |
|
Object item = s.item; |
| 607 |
|
if (item != e) { // matched |
| 608 |
+ |
assert item != s; |
| 609 |
|
s.forgetContents(); // avoid garbage |
| 610 |
< |
return item; |
| 610 |
> |
return this.<E>cast(item); |
| 611 |
|
} |
| 612 |
< |
if ((w.isInterrupted() || (how == TIMEOUT && nanos <= 0)) && |
| 613 |
< |
s.casItem(e, s)) { // cancel |
| 612 |
> |
if ((w.isInterrupted() || (timed && nanos <= 0)) && |
| 613 |
> |
s.casItem(e, s)) { // cancel |
| 614 |
|
unsplice(pred, s); |
| 615 |
|
return e; |
| 616 |
|
} |
| 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; |
| 678 |
< |
Node n = p.next; |
| 679 |
< |
p = (n != p) ? n : head; |
| 701 |
> |
return (p.isData == isData) ? p : null; |
| 702 |
|
} |
| 703 |
|
return null; |
| 704 |
|
} |
| 705 |
|
|
| 706 |
|
/** |
| 707 |
|
* Returns the item in the first unmatched node with isData; or |
| 708 |
< |
* null if none. Used by peek. |
| 708 |
> |
* null if none. Used by peek. |
| 709 |
|
*/ |
| 710 |
< |
private Object firstDataItem() { |
| 711 |
< |
for (Node p = head; p != null; ) { |
| 690 |
< |
boolean isData = p.isData; |
| 710 |
> |
private E firstDataItem() { |
| 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 ? 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 |
|
} |
| 746 |
|
|
| 747 |
|
final class Itr implements Iterator<E> { |
| 748 |
|
private Node nextNode; // next node to return item for |
| 749 |
< |
private Object nextItem; // the corresponding item |
| 749 |
> |
private E nextItem; // the corresponding item |
| 750 |
|
private Node lastRet; // last returned node, to support remove |
| 751 |
+ |
private Node lastPred; // predecessor to unlink lastRet |
| 752 |
|
|
| 753 |
|
/** |
| 754 |
|
* Moves to next node after prev, or first node if prev null. |
| 755 |
|
*/ |
| 756 |
|
private void advance(Node prev) { |
| 757 |
+ |
lastPred = lastRet; |
| 758 |
|
lastRet = prev; |
| 759 |
< |
Node p; |
| 760 |
< |
if (prev == null || (p = prev.next) == prev) |
| 736 |
< |
p = head; |
| 737 |
< |
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) { |
| 764 |
< |
nextItem = item; |
| 764 |
> |
nextItem = LinkedTransferQueue.this.<E>cast(item); |
| 765 |
|
nextNode = p; |
| 766 |
|
return; |
| 767 |
|
} |
| 768 |
|
} |
| 769 |
|
else if (item == null) |
| 770 |
|
break; |
| 748 |
– |
Node n = p.next; |
| 749 |
– |
p = (n != p) ? n : head; |
| 771 |
|
} |
| 772 |
|
nextNode = null; |
| 773 |
|
} |
| 783 |
|
public final E next() { |
| 784 |
|
Node p = nextNode; |
| 785 |
|
if (p == null) throw new NoSuchElementException(); |
| 786 |
< |
Object e = nextItem; |
| 786 |
> |
E e = nextItem; |
| 787 |
|
advance(p); |
| 788 |
< |
return (E) e; |
| 788 |
> |
return e; |
| 789 |
|
} |
| 790 |
|
|
| 791 |
|
public final void remove() { |
| 792 |
|
Node p = lastRet; |
| 793 |
|
if (p == null) throw new IllegalStateException(); |
| 794 |
< |
lastRet = null; |
| 774 |
< |
findAndRemoveNode(p); |
| 794 |
> |
findAndRemoveDataNode(lastPred, p); |
| 795 |
|
} |
| 796 |
|
} |
| 797 |
|
|
| 825 |
|
break; |
| 826 |
|
} |
| 827 |
|
if (oldpred == pred || // Already saved |
| 828 |
< |
(oldpred == null && casCleanMe(null, pred))) |
| 829 |
< |
break; // Postpone cleaning |
| 828 |
> |
((oldpred == null || oldpred.next == s) && |
| 829 |
> |
casCleanMe(oldpred, pred))) { |
| 830 |
> |
break; |
| 831 |
> |
} |
| 832 |
|
} |
| 833 |
|
} |
| 834 |
|
} |
| 868 |
|
} |
| 869 |
|
|
| 870 |
|
/** |
| 871 |
< |
* Main implementation of Iterator.remove(). Find |
| 872 |
< |
* and unsplice the given 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 |
|
*/ |
| 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 |
|
} |
| 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; |
| 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, TIMED, 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 |
|
/** |
| 1218 |
|
} |
| 1219 |
|
} |
| 1220 |
|
|
| 1195 |
– |
|
| 1221 |
|
// Unsafe mechanics |
| 1222 |
|
|
| 1223 |
|
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
| 1240 |
|
} |
| 1241 |
|
} |
| 1242 |
|
|
| 1243 |
< |
private static sun.misc.Unsafe getUnsafe() { |
| 1243 |
> |
/** |
| 1244 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
| 1245 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
| 1246 |
> |
* into a jdk. |
| 1247 |
> |
* |
| 1248 |
> |
* @return a sun.misc.Unsafe |
| 1249 |
> |
*/ |
| 1250 |
> |
static sun.misc.Unsafe getUnsafe() { |
| 1251 |
|
try { |
| 1252 |
|
return sun.misc.Unsafe.getUnsafe(); |
| 1253 |
|
} catch (SecurityException se) { |
