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#ifndef QPID_BROKER_OBSERVERS_H
#define QPID_BROKER_OBSERVERS_H
/*
*
* 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.
*
*/
#include "qpid/sys/Mutex.h"
#include <boost/shared_ptr.hpp>
#include <set>
#include <algorithm>
namespace qpid {
namespace broker {
/**
* Base class for collections of observers with thread-safe add/remove and traversal.
*/
template <class Observer>
class Observers
{
public:
typedef boost::shared_ptr<Observer> ObserverPtr;
void add(const ObserverPtr& observer) {
sys::Mutex::ScopedLock l(lock);
observers.insert(observer);
}
void remove(const ObserverPtr& observer) {
sys::Mutex::ScopedLock l(lock);
observers.erase(observer) ;
}
/** Iterate over the observers. */
template <class F> void each(F f) {
Set copy; // Make a copy and iterate outside the lock.
{
sys::Mutex::ScopedLock l(lock);
copy = observers;
}
std::for_each(copy.begin(), copy.end(), f);
}
template <class T> boost::shared_ptr<T> findType() const {
sys::Mutex::ScopedLock l(lock);
typename Set::const_iterator i =
std::find_if(observers.begin(), observers.end(), &isA<T>);
return i == observers.end() ?
boost::shared_ptr<T>() : boost::dynamic_pointer_cast<T>(*i);
}
protected:
typedef std::set<ObserverPtr> Set;
Observers() : lock(myLock) {}
/** Specify a lock for the Observers to use */
Observers(sys::Mutex& l) : lock(l) {}
/** Iterate over the observers without taking the lock, caller must hold the lock */
template <class F> void each(F f, const sys::Mutex::ScopedLock&) {
std::for_each(observers.begin(), observers.end(), f);
}
template <class T> static bool isA(const ObserverPtr&o) {
return !!boost::dynamic_pointer_cast<T>(o);
}
mutable sys::Mutex myLock;
sys::Mutex& lock;
Set observers;
};
}} // namespace qpid::broker
#endif /*!QPID_BROKER_OBSERVERS_H*/
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