/** {@inheritDoc} */
public E pollAcquire(Object owner) {
E element;
// Find an element on the requeue that is free and return it.
if (!requeue.isEmpty()) {
for (RequeueElementWrapper<E> nextRecord : requeue) {
if (AcquireState.Free.equals(nextRecord.state)) {
nextRecord.state = AcquireState.Acquired;
nextRecord.owner = owner;
return nextRecord.element;
}
}
}
// Nothing could be found on the requeue, so attempt to poll an element off the main queue and
// acquire
// it on the requeue.
element = queue.poll();
if (element != null) {
requeue(element, owner, AcquireState.Acquired);
}
return element;
}
/**
* Places an element onto the requeue buffer, in the acquired state by the specified owner.
*
* @param element The element to place onto the requeue buffer.
* @param owner The owner of the acquired element.
* @param acquired The acquired state to set on the element in the requeue.
* @return The requeue element wrapper for the requeued element.
*/
private RequeueElementWrapper<E> requeue(E element, Object owner, AcquireState acquired) {
RequeueElementWrapper<E> record = new RequeueElementWrapper<E>(element);
record.state = acquired;
record.owner = owner;
requeue.add(record);
requeuedElementMap.put(element, record);
return record;
}
/** {@inheritDoc} */
public void release(Object owner, Object o) {
// Look up the element wrapper record for the element to be released, and release it.
RequeueElementWrapper<E> record = requeuedElementMap.get(o);
if (record != null) {
record.state = AcquireState.Free;
record.owner = null;
}
}
/** {@inheritDoc} */
public boolean acquire(Object owner, Object o) {
// Look up the element wrapper record for the element to be accepted.
RequeueElementWrapper<E> record = requeuedElementMap.get(o);
// Check if the element is currently free, and acquire it if so.
if (AcquireState.Free.equals(record.state)) {
record.state = AcquireState.Acquired;
record.owner = owner;
return true;
}
return false;
}
/** {@inheritDoc} */
public E pollAccept(Object owner) {
if (transactional) {
E element = null;
RequeueElementWrapper<E> record = null;
// Find an element on the requeue that is free, or has already been acquired by the owner but
// not accepted.
// Mark the element as acquired by the owner as necessary.
if (!requeue.isEmpty()) {
for (RequeueElementWrapper<E> nextRecord : requeue) {
if (AcquireState.Free.equals(nextRecord.state)) {
record = nextRecord;
record.state = AcquireState.Acquired;
record.owner = owner;
element = record.element;
break;
} else if (AcquireState.Acquired.equals(nextRecord.state)
&& owner.equals(nextRecord.owner)) {
record = nextRecord;
element = record.element;
break;
}
}
}
// If an element cannot be found on the requeue, poll an element from the main queue, and
// place it onto the
// requeue.
if (record == null) {
element = queue.poll();
}
// If no element at all can be found return null.
if (element == null) {
return element;
}
// Check that an element was actually available on the queue before creating a new acquired
// record for it
// on the requeue.
if (record == null) {
record = requeue(element, owner, AcquireState.Acquired);
}
// Accept the element and create a transaction operation to remove it upon commit or unnaccept
// it upon
// rollback.
record.state = AcquireState.Accepted;
txMethod.requestWriteOperation(new AcceptRecord(record));
return record.element;
} else {
E element;
// Find an element on the requeue that is free. Remove it and return it.
if (!requeue.isEmpty()) {
for (RequeueElementWrapper<E> nextRecord : requeue) {
if (AcquireState.Free.equals(nextRecord.state)) {
requeue.remove(nextRecord);
requeuedElementMap.remove(nextRecord.element);
return nextRecord.element;
}
}
}
// Or poll an element from the main queue and return it.
element = queue.poll();
if (element != null) {
decrementSizeAndCount(element);
}
return element;
}
}