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/* Copyright (C) 2013 BMW Group
* Author: Manfred Bathelt (manfred.bathelt@bmw.de)
* Author: Juergen Gehring (juergen.gehring@bmw.de)
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#if !defined (COMMONAPI_INTERNAL_COMPILATION)
#error "Only <CommonAPI/CommonAPI.h> can be included directly, this file may disappear or change contents."
#endif
#ifndef COMMONAPI_EVENT_H_
#define COMMONAPI_EVENT_H_
#include <functional>
#include <list>
#include <tuple>
#include <mutex>
namespace CommonAPI {
enum class SubscriptionStatus {
RETAIN,
CANCEL
};
/**
* \brief Class representing an event
*
* Class representing an event
*/
template <typename... _Arguments>
class Event {
public:
typedef std::tuple<_Arguments...> ArgumentsTuple;
typedef std::function<void(const _Arguments&...)> Listener;
typedef std::function<SubscriptionStatus(const _Arguments&...)> CancellableListener;
typedef std::list<CancellableListener> ListenersList;
typedef typename ListenersList::iterator Subscription;
class CancellableListenerWrapper;
/**
* \brief Subscribe a listener to this event
*
* Subscribe a listener to this event.
* ATTENTION: You should not build new proxies or register services in callbacks
* from events. This can cause a deadlock or assert. Instead, you should set a
* trigger for your application to do this on the next iteration of your event loop
* if needed. The preferred solution is to build all proxies you need at the
* beginning and react to events appropriatly for each.
*
* @param listener A listener to be added
* @return A token identifying this subscription
*/
inline Subscription subscribe(Listener listener);
/**
* \brief Subscribe a cancellable listener to this event
*
* Subscribe a cancellable listener to this event
* ATTENTION: You should not build new proxies or register services in callbacks
* from events. This can cause a deadlock or assert. Instead, you should set a
* trigger for your application to do this on the next iteration of your event loop
* if needed. The preferred solution is to build all proxies you need at the
* beginning and react to events appropriatly for each.
*
* @param listener A cancellable listener to be added
* @return A token identifying this subscription
*/
Subscription subscribeCancellableListener(CancellableListener listener);
/**
* \brief Remove a listener from this event
*
* Remove a listener from this event
* Note: Do not call this inside a listener notification callback it will deadlock! Use cancellable listeners instead.
*
* @param listenerSubscription A listener token to be removed
*/
void unsubscribe(Subscription listenerSubscription);
virtual ~Event() {}
protected:
// Returns false if all subscriptions were cancelled
// Does not send *Removed events!
SubscriptionStatus notifyListeners(const _Arguments&... eventArguments);
// Events sent during subscribe()
virtual void onFirstListenerAdded(const CancellableListener& listener) { }
virtual void onListenerAdded(const CancellableListener& listener) { }
// Events sent during unsubscribe()
virtual void onListenerRemoved(const CancellableListener& listener) { }
virtual void onLastListenerRemoved(const CancellableListener& listener) { }
inline bool hasListeners() const;
private:
ListenersList listenersList_;
std::mutex listenerListMutex_;
};
template <typename... _Arguments>
class Event<_Arguments...>::CancellableListenerWrapper {
public:
CancellableListenerWrapper(Listener&& listener): listener_(std::move(listener)) {
}
SubscriptionStatus operator()(const _Arguments&... eventArguments) {
listener_(eventArguments...);
return SubscriptionStatus::RETAIN;
}
private:
Listener listener_;
};
template <typename... _Arguments>
typename Event<_Arguments...>::Subscription Event<_Arguments...>::subscribe(Listener listener) {
return subscribeCancellableListener(CancellableListenerWrapper(std::move(listener)));
}
template <typename... _Arguments>
typename Event<_Arguments...>::Subscription Event<_Arguments...>::subscribeCancellableListener(CancellableListener listener) {
listenerListMutex_.lock();
const bool firstListenerAdded = listenersList_.empty();
listenersList_.emplace_front(std::move(listener));
Subscription listenerSubscription = listenersList_.begin();
listenerListMutex_.unlock();
if (firstListenerAdded) {
onFirstListenerAdded(*listenerSubscription);
}
onListenerAdded(*listenerSubscription);
return listenerSubscription;
}
template <typename... _Arguments>
void Event<_Arguments...>::unsubscribe(Subscription listenerSubscription) {
const CancellableListener cancellableListener = *listenerSubscription;
listenerListMutex_.lock();
listenersList_.erase(listenerSubscription);
const bool lastListenerRemoved = listenersList_.empty();
listenerListMutex_.unlock();
onListenerRemoved(cancellableListener);
if (lastListenerRemoved) {
onLastListenerRemoved(cancellableListener);
}
}
template <typename... _Arguments>
SubscriptionStatus Event<_Arguments...>::notifyListeners(const _Arguments&... eventArguments) {
listenerListMutex_.lock();
for (auto iterator = listenersList_.begin(); iterator != listenersList_.end(); ) {
const CancellableListener& cancellableListener = *iterator;
const SubscriptionStatus listenerSubscriptionStatus = cancellableListener(eventArguments...);
if (listenerSubscriptionStatus == SubscriptionStatus::CANCEL) {
auto listenerIterator = iterator;
iterator++;
listenersList_.erase(listenerIterator);
} else
iterator++;
}
const bool lEmpty = listenersList_.empty();
listenerListMutex_.unlock();
return lEmpty ? SubscriptionStatus::CANCEL : SubscriptionStatus::RETAIN;
}
template <typename... _Arguments>
bool Event<_Arguments...>::hasListeners() const {
return !listenersList_.empty();
}
} // namespace CommonAPI
#endif // COMMONAPI_EVENT_H_
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