private Token receive0() {
Node s = new Node(null, false); // the node to append
retry:
for (; ; ) { // restart on append race
Object item = tryMatch(null, null, false);
if (item != NO_MATCH) {
s.item = item;
return new Token(s, null);
}
Node pred = tryAppend(s, false);
if (pred == null) continue retry; // lost race vs opposite mode
if (sendClosed) {
s.item = CHANNEL_CLOSED;
unsplice(pred, s);
setReceiveClosed();
return new Token(s, null);
}
requestUnpark(s, Strand.currentStrand());
return new Token(s, pred);
}
}
@Override
public boolean send(Message message, long timeout, TimeUnit unit)
throws SuspendExecution, InterruptedException {
if (message == null) throw new IllegalArgumentException("message is null");
if (isSendClosed()) return true;
if (xfer1(message, true, TIMED, unit.toNanos(timeout)) == null) return true;
if (!Strand.interrupted()) return false;
throw new InterruptedException();
}
/** Tries to artificially match a data node -- used by remove. */
final boolean tryMatchData() {
// assert isData;
Object x = item;
if (x != null && x != this && casItem(x, null)) {
Strand.unpark(waiter, this);
return true;
}
return false;
}
protected Message receiveInternal(long timeout, TimeUnit unit)
throws SuspendExecution, InterruptedException {
if (receiveClosed) return null;
Object m = xfer1(null, false, TIMED, unit.toNanos(timeout));
if (m != null || !Strand.interrupted()) {
if (m == CHANNEL_CLOSED) return closeValue();
return (Message) m;
}
throw new InterruptedException();
}
private Object tryMatch(SelectActionImpl sa, Message e, boolean haveData) {
boolean closed = isSendClosed(); // must be read before trying to match so as not to miss puts
for (Node h = head, p = h; p != null; ) { // find & match first node
boolean isData = p.isData;
Object item = p.item;
if (item != p && (item != null) == isData) { // unmatched
if (isData == haveData) // can't match
break;
// avoid deadlock by orderdering lease acquisition:
// if p requires a lease and is of lower hashCode than sa, we return sa's lease, acquire
// p's, and then reacquire sa's.
SelectActionImpl sa2 = p.sa;
boolean leasedp;
if (sa != null && sa2 != null && sa2.selector().id < sa.selector().id) {
sa.returnLease();
leasedp = sa2.lease();
if (!sa.lease()) {
if (leasedp) sa2.returnLease();
return LOST;
}
} else leasedp = p.lease();
if (leasedp) {
if (p.casItem(item, e)) { // match
p.won();
for (Node q = p; q != h; ) {
Node n = q.next; // update by 2 unless singleton
if (head == h && casHead(h, n == null ? q : n)) {
h.forgetNext();
break;
} // advance and retry
if ((h = head) == null || (q = h.next) == null || !q.isMatched())
break; // unless slack < 2
}
Strand.unpark(p.waiter, this);
return item;
} else p.returnLease();
}
}
Node n = p.next;
p = (p != n) ? n : (h = head); // Use head if p offlist
}
if (closed) {
assert !haveData;
setReceiveClosed();
return CHANNEL_CLOSED;
}
return NO_MATCH;
}
@Suspendable
public static void handleDelayWithStrand() {
if (delay > 0) {
try {
Strand.sleep(delay);
} catch (final InterruptedException ie) {
ie.printStackTrace(System.err);
throw new RuntimeException(ie);
} catch (final SuspendExecution se) {
throw new AssertionError(se);
}
}
}
private void signalWaitersOnClose() {
for (Node p = head; p != null; ) {
if (!p.isMatched()) {
if (!p.isData) {
if (p.casItem(null, CHANNEL_CLOSED)) // match waiting requesters with CHANNEL_CLOSED
Strand.unpark(p.waiter, this); // ... and wake 'em up
} else p.tryMatchData();
}
Node n = p.next;
if (n != p) p = n;
else p = head;
}
}
private static ActorRef getCurrentActor() {
ActorRef actorRef = LocalActor.self();
if (actorRef == null) {
// create a "dummy actor" on the current strand
Actor actor =
new Actor(Strand.currentStrand(), null, new MailboxConfig(5, OverflowPolicy.THROW)) {
@Override
protected Object doRun() throws InterruptedException, SuspendExecution {
throw new AssertionError();
}
};
actorRef = new TempActor(actor);
}
return actorRef;
}
/**
* Spins/yields/blocks until node s is matched or caller gives up.
*
* @param s the waiting node
* @param pred the predecessor of s, or s itself if it has no predecessor, or null if unknown (the
* null case does not occur in any current calls but may in possible future extensions)
* @param e the comparison value for checking match
* @param timed if true, wait only until timeout elapses
* @param nanos timeout in nanosecs, used only if timed is true
* @return matched item, or e if unmatched on interrupt or timeout
*/
private Message awaitMatch(Node s, Node pred, Message e, boolean timed, long nanos)
throws SuspendExecution {
long lastTime = timed ? System.nanoTime() : 0L;
Strand w = Strand.currentStrand();
int spins =
(w.isFiber()
? 0
: -1); // no spins in fiber; otherwise, initialized after first item and cancel checks
ThreadLocalRandom randomYields = null; // bound if needed
if (spins == 0) requestUnpark(s, w);
for (; ; ) {
Object item = s.item;
if (item == CHANNEL_CLOSED) setReceiveClosed();
if (item != e) { // matched
// assert item != s;
s.forgetContents(); // avoid garbage
return this.<Message>cast(item);
}
if ((w.isInterrupted() || (timed && nanos <= 0)) && s.casItem(e, s)) { // cancel
unsplice(pred, s);
return e;
}
if (spins < 0) { // establish spins at/near front
if ((spins = spinsFor(pred, s.isData)) > 0) randomYields = ThreadLocalRandom.current();
} else if (spins > 0) { // spin
--spins;
if (randomYields.nextInt(CHAINED_SPINS) == 0) Strand.yield(); // occasionally yield
} else if (s.waiter == null) {
requestUnpark(s, w); // request unpark then recheck
} else if (timed) {
long now = System.nanoTime();
if ((nanos -= now - lastTime) > 0) Strand.parkNanos(this, nanos);
lastTime = now;
} else {
Strand.park(this);
}
}
}
