/**
* Retrieves and removes the head of this queue, waiting if necessary until an element with an
* expired delay is available on this queue, or the specified wait time expires.
*
* @return the head of this queue, or <tt>null</tt> if the specified waiting time elapses before
* an element with an expired delay becomes available
* @throws InterruptedException {@inheritDoc}
*/
public E poll(long timeout, TimeUnit unit) throws InterruptedException {
long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
for (; ; ) {
E first = q.peek();
if (first == null) {
if (nanos <= 0) return null;
else nanos = available.awaitNanos(nanos);
} else {
long delay = first.getDelay(TimeUnit.NANOSECONDS);
if (delay > 0) {
if (nanos <= 0) return null;
if (delay > nanos) delay = nanos;
long timeLeft = available.awaitNanos(delay);
nanos -= delay - timeLeft;
} else {
E x = q.poll();
assert x != null;
if (q.size() != 0) available.signalAll();
return x;
}
}
}
} finally {
lock.unlock();
}
}
public int size() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return q.size();
} finally {
lock.unlock();
}
}
/**
* Retrieves and removes the head of this queue, or returns <tt>null</tt> if this queue has no
* elements with an expired delay.
*
* @return the head of this queue, or <tt>null</tt> if this queue has no elements with an expired
* delay
*/
public E poll() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
E first = q.peek();
if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0) return null;
else {
E x = q.poll();
assert x != null;
if (q.size() != 0) available.signalAll();
return x;
}
} finally {
lock.unlock();
}
}
/**
* Retrieves and removes the head of this queue, waiting if necessary until an element with an
* expired delay is available on this queue.
*
* @return the head of this queue
* @throws InterruptedException {@inheritDoc}
*/
public E take() throws InterruptedException {
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
for (; ; ) {
E first = q.peek();
if (first == null) {
available.await();
} else {
long delay = first.getDelay(TimeUnit.NANOSECONDS);
if (delay > 0) {
long tl = available.awaitNanos(delay);
} else {
E x = q.poll();
assert x != null;
if (q.size() != 0) available.signalAll(); // wake up other takers
return x;
}
}
}
} finally {
lock.unlock();
}
}
