private synchronized void updateState() {
if (closed.get()) {
// remove all empty queues
for (Iterator<NamedQueue> iterator = openQueuesBySequenceId.iterator();
iterator.hasNext(); ) {
NamedQueue namedQueue = iterator.next();
if (namedQueue.isEmpty()) {
namedQueue.setFinished();
iterator.remove();
}
}
// discard queued pages (not officially in the buffer) and waiters
for (QueuedPage queuedPage : queuedPages) {
queuedPage.getFuture().set(null);
}
queuedPages.clear();
}
if (state == QueueState.NO_MORE_QUEUES && !openQueuesBySequenceId.isEmpty()) {
// advance master sequence id
long oldMasterSequenceId = masterSequenceId;
masterSequenceId = openQueuesBySequenceId.iterator().next().getSequenceId();
// drop consumed pages
int pagesToRemove = Ints.checkedCast(masterSequenceId - oldMasterSequenceId);
Preconditions.checkState(
pagesToRemove >= 0,
"Master sequence id moved backwards: oldMasterSequenceId=%s, newMasterSequenceId=%s",
oldMasterSequenceId,
masterSequenceId);
for (int i = 0; i < pagesToRemove; i++) {
Page page = masterQueue.removeFirst();
bufferedBytes -= page.getDataSize().toBytes();
}
// refill buffer from queued pages
while (!queuedPages.isEmpty() && bufferedBytes < maxBufferedBytes) {
QueuedPage queuedPage = queuedPages.removeFirst();
addInternal(queuedPage.getPage());
queuedPage.getFuture().set(null);
}
}
if (state == QueueState.NO_MORE_QUEUES && closed.get() && openQueuesBySequenceId.isEmpty()) {
destroy();
}
this.notifyAll();
}
public synchronized ListenableFuture<?> enqueue(Page page) {
Preconditions.checkNotNull(page, "page is null");
// is the output done
if (closed.get()) {
return Futures.immediateFuture(true);
}
// is there room in the buffer
if (bufferedBytes < maxBufferedBytes) {
addInternal(page);
return Futures.immediateFuture(true);
}
QueuedPage queuedPage = new QueuedPage(page);
queuedPages.addLast(queuedPage);
return queuedPage.getFuture();
}
/** Destroys the queue, discarding all pages. */
public synchronized void destroy() {
closed.set(true);
state = QueueState.FINISHED;
// drop all of the queues
for (NamedQueue namedQueue : openQueuesBySequenceId) {
namedQueue.setFinished();
}
openQueuesBySequenceId.clear();
// clear the buffer
masterQueue.clear();
bufferedBytes = 0;
// free queued page waiters
for (QueuedPage queuedPage : queuedPages) {
queuedPage.getFuture().set(null);
}
queuedPages.clear();
// notify readers that the buffer has been destroyed
this.notifyAll();
}