package org.mortbay.cometd.ext;
import java.util.Map;
import java.util.Queue;
import org.cometd.Bayeux;
import org.cometd.Client;
import org.cometd.Extension;
import org.cometd.Message;
import org.mortbay.cometd.MessageImpl;
/**
* Acknowledged Message Client extension.
*
* Tracks the batch id of messages sent to a client.
*
*/
public class AcknowledgedMessagesClientExtension implements Extension
{
private final Client _client;
private final ArrayIdQueue<Message> _unackedQueue;
private long _lastAck;
public AcknowledgedMessagesClientExtension(Client client)
{
_client=client;
_unackedQueue=new ArrayIdQueue<Message>(8,16,client);
_unackedQueue.setCurrentId(1);
}
public Message rcv(Client from, Message message)
{
return message;
}
/**
* Handle received meta messages. Looks for meta/connect messages with
* ext/ack fields. If present, delete all messages that have been acked and
* requeue messages that have not been acked.
*/
public Message rcvMeta(Client from, Message message)
{
if (message.getChannel().equals(Bayeux.META_CONNECT))
{
synchronized(_client)
{
Map<String,Object> ext=message.getExt(false);
if (ext != null)
{
Long acked=(Long)ext.get("ack");
if (acked != null)
{
final int s=_unackedQueue.size();
if (acked<=_lastAck)
{
Queue<Message> clientQueue = from.getQueue();
clientQueue.clear();
for (int i=0; i < s; ++i)
{
Message m = _unackedQueue.getUnsafe(i);
if (m instanceof MessageImpl)
((MessageImpl)m).incRef();
clientQueue.add(m);
}
}
_lastAck=acked;
// We have received an ack ID, so delete the acked messages.
if (s > 0)
{
if (_unackedQueue.getAssociatedIdUnsafe(s - 1) <= acked)
{
// we can just clear the queue
for (int i=0; i < s; i++)
{
final Message q=_unackedQueue.getUnsafe(i);
if (q instanceof MessageImpl)
((MessageImpl)q).decRef();
}
_unackedQueue.clear();
}
else
{
// we need to remove elements until we see
// unacked
for (int i=0; i < s; i++)
{
if (_unackedQueue.getAssociatedIdUnsafe(0) <= acked)
{
final Message q=_unackedQueue.remove();
if (q instanceof MessageImpl)
((MessageImpl)q).decRef();
continue;
}
break;
}
}
}
}
}
}
}
return message;
}
public Message send(Client from, Message message)
{
synchronized(_client)
{
_unackedQueue.add(message);
// prevent the message from being erased
((MessageImpl)message).incRef();
}
return message;
}
public Message sendMeta(Client from, Message message)
{
if (message == null)
return message;
if (message.getChannel() == null)
return message;
if (message.getChannel().equals(Bayeux.META_CONNECT))
{
synchronized(_client)
{
Map<String,Object> ext=message.getExt(true);
ext.put("ack",_unackedQueue.getCurrentId());
_unackedQueue.incrementCurrentId();
}
}
return message;
}
}