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/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
package org.apache.qpid.server.queue;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
/**
* Distributes messages among a list of subsscription managers, using their
* weighting.
*
*/
class NestedSubscriptionManager implements SubscriptionManager
{
private final List<WeightedSubscriptionManager> _subscribers = new CopyOnWriteArrayList<WeightedSubscriptionManager>();
private int _iterations;
private int _index;
void addSubscription(WeightedSubscriptionManager s)
{
_subscribers.add(s);
}
void removeSubscription(WeightedSubscriptionManager s)
{
_subscribers.remove(s);
}
public boolean hasActiveSubscribers()
{
for(WeightedSubscriptionManager s : _subscribers)
{
if(s.hasActiveSubscribers())
{
return true;
}
}
return false;
}
public Subscription nextSubscriber(AMQMessage msg)
{
WeightedSubscriptionManager start = current();
for(WeightedSubscriptionManager s = start; s != null; s = next(start))
{
if(hasMore(s))
{
return nextSubscriber(s);
}
}
return null;
}
private Subscription nextSubscriber(WeightedSubscriptionManager s)
{
_iterations++;
return s.nextSubscriber(null);
}
private WeightedSubscriptionManager current()
{
return _subscribers.isEmpty() ? null : _subscribers.get(_index);
}
private boolean hasMore(WeightedSubscriptionManager s)
{
return _iterations < s.getWeight();
}
private WeightedSubscriptionManager next(WeightedSubscriptionManager start)
{
WeightedSubscriptionManager s = next();
return s == start && !hasMore(s) ? null : s;
}
private WeightedSubscriptionManager next()
{
_iterations = 0;
if(++_index >= _subscribers.size())
{
_index = 0;
}
return _subscribers.get(_index);
}
}
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