/*
* Quasar: lightweight threads and actors for the JVM.
* Copyright (C) 2013, Parallel Universe Software Co. All rights reserved.
*
* This program and the accompanying materials are dual-licensed under
* either the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation
*
* or (per the licensee's choosing)
*
* under the terms of the GNU Lesser General Public License version 3.0
* as published by the Free Software Foundation.
*/
package co.paralleluniverse.strands.channels;
import co.paralleluniverse.common.util.Objects;
import co.paralleluniverse.fibers.SuspendExecution;
import co.paralleluniverse.remote.RemoteProxyFactoryService;
import co.paralleluniverse.strands.Condition;
import co.paralleluniverse.strands.OwnedSynchronizer;
import co.paralleluniverse.strands.SimpleConditionSynchronizer;
import co.paralleluniverse.strands.Strand;
import co.paralleluniverse.strands.channels.Channels.OverflowPolicy;
import co.paralleluniverse.strands.queues.BasicQueue;
import co.paralleluniverse.strands.queues.CircularBuffer;
import co.paralleluniverse.strands.queues.QueueCapacityExceededException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
/**
*
* @author pron
*/
public abstract class QueueChannel<Message> implements Channel<Message>, Selectable<Message>, java.io.Serializable {
private static final int MAX_SEND_RETRIES = 10;
final Condition sync;
final Condition sendersSync;
final BasicQueue<Message> queue;
final OverflowPolicy overflowPolicy;
private volatile boolean sendClosed;
private boolean receiveClosed;
protected QueueChannel(BasicQueue<Message> queue, OverflowPolicy overflowPolicy, boolean singleConsumer) {
this.queue = queue;
if (!singleConsumer || queue instanceof CircularBuffer)
this.sync = new SimpleConditionSynchronizer();
else
this.sync = new OwnedSynchronizer();
this.overflowPolicy = overflowPolicy;
this.sendersSync = overflowPolicy == OverflowPolicy.BLOCK ? new SimpleConditionSynchronizer() : null;
}
public int capacity() {
return queue.capacity();
}
protected Condition sync() {
verifySync();
return sync;
}
protected void signalReceivers() {
sync.signalAll();
}
protected void signalAndTryToExecNow() {
if (sync instanceof OwnedSynchronizer)
((OwnedSynchronizer) sync).signalAndTryToExecNow();
else
sync.signalAll();
}
void signalSenders() {
if (overflowPolicy == OverflowPolicy.BLOCK)
sendersSync.signal();
}
@Override
public Object register(SelectAction<Message> action) {
if (action.isData()) {
if (sendersSync != null)
sendersSync.register();
} else
sync.register();
return action;
}
@Override
public boolean tryNow(Object token) {
SelectAction<Message> action = (SelectAction<Message>) token;
if (!action.lease())
return false;
boolean res;
if (action.isData()) {
res = trySend(action.message());
if (res)
action.setItem(null);
} else {
Message m = tryReceive();
action.setItem(m);
if (m == null)
res = isClosed();
else
res = true;
}
if (res)
action.won();
else
action.returnLease();
return res;
}
@Override
public void unregister(Object token) {
if (token == null)
return;
SelectAction<Message> action = (SelectAction<Message>) token;
if (action.isData()) {
if (sendersSync != null)
sendersSync.unregister();
} else
sync.unregister();
}
public void sendNonSuspendable(Message message) throws QueueCapacityExceededException {
if (isSendClosed())
return;
if (!queue.enq(message))
throw new QueueCapacityExceededException();
signalReceivers();
}
@Override
public void send(Message message) throws SuspendExecution, InterruptedException {
send0(message, false, false, 0);
}
@Override
public boolean send(Message message, long timeout, TimeUnit unit) throws SuspendExecution, InterruptedException {
throw new UnsupportedOperationException("Not supported yet.");
}
@Override
public boolean trySend(Message message) {
if (message == null)
throw new IllegalArgumentException("message is null");
if (isSendClosed())
return true;
if (queue.enq(message)) {
signalReceivers();
return true;
} else
return false;
}
protected void sendSync(Message message) throws SuspendExecution {
try {
send0(message, true, false, 0);
} catch (InterruptedException e) {
Strand.currentStrand().interrupt();
}
}
public boolean send0(Message message, boolean sync, boolean timed, long nanos) throws SuspendExecution, InterruptedException {
if (message == null)
throw new IllegalArgumentException("message is null");
if (isSendClosed())
return true;
if (overflowPolicy == OverflowPolicy.BLOCK)
sendersSync.register();
try {
int i = 0;
while (!queue.enq(message)) {
if (isSendClosed())
return true;
onQueueFull(i++, false, 0);
}
} catch (TimeoutException e) {
return false;
} finally {
if (overflowPolicy == OverflowPolicy.BLOCK)
sendersSync.unregister();
}
if (sync)
signalAndTryToExecNow();
else
signalReceivers();
return true;
}
void onQueueFull(int iter, boolean timed, long nanos) throws SuspendExecution, InterruptedException, TimeoutException {
switch (overflowPolicy) {
case DROP:
return;
case THROW:
throw new QueueCapacityExceededException();
case BLOCK:
if (timed) {
if (nanos > 0) {
if (sendersSync.await(iter, nanos, TimeUnit.NANOSECONDS))
return;
}
throw new TimeoutException();
} else
sendersSync.await(iter);
break;
case BACKOFF:
if (iter > MAX_SEND_RETRIES)
throw new QueueCapacityExceededException();
if (iter > 5)
Strand.sleep((iter - 5) * 5);
else if (iter > 4)
Strand.yield();
}
}
@Override
public void close() {
if (!sendClosed) {
sendClosed = true;
signalReceivers();
if (sendersSync != null)
sendersSync.signalAll();
}
}
/**
* This method must only be called by the channel's owner (the receiver)
*
* @return
*/
@Override
public boolean isClosed() {
return receiveClosed;
}
boolean isSendClosed() {
return sendClosed;
}
void setReceiveClosed() {
this.receiveClosed = true;
}
@Override
public Message tryReceive() {
if (receiveClosed)
return null;
boolean closed = isSendClosed();
final Message m = queue.poll();
if (m != null)
signalSenders();
else if (closed)
setReceiveClosed();
return m;
}
@Override
public Message receive() throws SuspendExecution, InterruptedException {
if (receiveClosed)
return null;
Message m;
boolean closed;
sync.register();
for (int i = 0;; i++) {
closed = isSendClosed(); // must be read BEFORE queue.poll()
if ((m = queue.poll()) != null)
break;
if (closed) {
setReceiveClosed();
return null;
}
sync.await(i);
}
sync.unregister();
assert m != null;
signalSenders();
return m;
}
@Override
public Message receive(long timeout, TimeUnit unit) throws SuspendExecution, InterruptedException {
if (receiveClosed)
return null;
if (unit == null)
return receive();
if (timeout <= 0)
return tryReceive();
final long start = System.nanoTime();
long left = unit.toNanos(timeout);
Message m;
boolean closed;
sync.register();
try {
for (int i = 0;; i++) {
closed = isSendClosed(); // must be read BEFORE queue.poll()
if ((m = queue.poll()) != null)
break;
if (closed) {
setReceiveClosed();
return null;
}
sync.await(i, left, TimeUnit.NANOSECONDS);
left = start + unit.toNanos(timeout) - System.nanoTime();
if (left <= 0)
return null;
}
} finally {
sync.unregister();
}
if (m != null)
signalSenders();
return m;
}
public Message receiveFromThread() throws InterruptedException {
try {
return receive();
} catch (SuspendExecution ex) {
throw new AssertionError(ex);
}
}
public Message receiveFromThread(long timeout, TimeUnit unit) throws InterruptedException {
try {
return receive(timeout, unit);
} catch (SuspendExecution ex) {
throw new AssertionError(ex);
}
}
private void verifySync() {
if (sync == null)
throw new IllegalStateException("Owning strand has not been set");
}
public int getQueueLength() {
return queue.size();
}
@Override
public String toString() {
return "Channel{" + "sync: " + sync + ", queue: " + Objects.systemToString(queue) + '}';
}
protected Object writeReplace() throws java.io.ObjectStreamException {
return RemoteProxyFactoryService.create(this, null);
}
}