/**
* Tries to match node s to this node, if so, waking up thread. Fulfillers call tryMatch to
* identify their waiters. Waiters block until they have been matched.
*
* @param s the node to match
* @return true if successfully matched to s
*/
boolean tryMatch(SNode s) {
if (match == null && UNSAFE.compareAndSwapObject(this, matchOffset, null, s)) {
Thread w = waiter;
if (w != null) { // waiters need at most one unpark
waiter = null;
LockSupport.unpark(w);
}
return true;
}
return match == s;
}
/** Tries to CAS cleanMe slot. */
boolean casCleanMe(QNode cmp, QNode val) {
return cleanMe == cmp && UNSAFE.compareAndSwapObject(this, cleanMeOffset, cmp, val);
}
/** Tries to cas nt as new tail. */
void advanceTail(QNode t, QNode nt) {
if (tail == t) UNSAFE.compareAndSwapObject(this, tailOffset, t, nt);
}
/**
* Tries to cas nh as new head; if successful, unlink old head's next node to avoid garbage
* retention.
*/
void advanceHead(QNode h, QNode nh) {
if (h == head && UNSAFE.compareAndSwapObject(this, headOffset, h, nh))
h.next = h; // forget old next
}
/** Tries to cancel by CAS'ing ref to this as item. */
void tryCancel(Object cmp) {
UNSAFE.compareAndSwapObject(this, itemOffset, cmp, this);
}
boolean casItem(Object cmp, Object val) {
return item == cmp && UNSAFE.compareAndSwapObject(this, itemOffset, cmp, val);
}
boolean casNext(QNode cmp, QNode val) {
return next == cmp && UNSAFE.compareAndSwapObject(this, nextOffset, cmp, val);
}
boolean casHead(SNode h, SNode nh) {
return h == head && UNSAFE.compareAndSwapObject(this, headOffset, h, nh);
}
/** Tries to cancel a wait by matching node to itself. */
void tryCancel() {
UNSAFE.compareAndSwapObject(this, matchOffset, null, this);
}
boolean casNext(SNode cmp, SNode val) {
return cmp == next && UNSAFE.compareAndSwapObject(this, nextOffset, cmp, val);
}