private Token xfer0(SelectActionImpl<Message> e) {
final boolean haveData = e.isData();
Node s = null; // the node to append, if needed
retry:
for (; ; ) { // restart on append race
if (!e.lease()) return null;
if (isClosed() || (isSendClosed() && e.isData())) {
e.setItem(null);
e.won();
return null;
}
Object item = tryMatch(e, e.message(), haveData);
if (item == LOST) return null;
if (item != NO_MATCH) {
e.setItem(item == CHANNEL_CLOSED ? null : (Message) item);
e.won();
return null;
}
e.returnLease();
if (s == null) {
s = new Node(e);
requestUnpark(s, e.selector().getWaiter());
}
Node pred = tryAppend(s, haveData);
if (pred == null) continue retry; // lost race vs opposite mode
return new Token(s, pred);
}
}
/**
* Constructs a new node. Uses relaxed write because item can only be seen after publication via
* casNext.
*/
Node(SelectActionImpl sa) {
UNSAFE.putObject(this, itemOffset, sa.message()); // relaxed write
UNSAFE.putObject(this, saOffset, sa); // relaxed write
this.isData = sa.isData();
}
