ClickHouse/base/poco/Foundation/include/Poco/AbstractEvent.h

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//
// AbstractEvent.h
//
// Library: Foundation
// Package: Events
// Module: AbstractEvent
//
// Definition of the AbstractEvent class.
//
// Copyright (c) 2006-2011, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#ifndef Foundation_AbstractFoundation_INCLUDED
#define Foundation_AbstractFoundation_INCLUDED
#include "Poco/ActiveMethod.h"
#include "Poco/ActiveResult.h"
#include "Poco/Foundation.h"
#include "Poco/Mutex.h"
#include "Poco/SharedPtr.h"
#include "Poco/SingletonHolder.h"
namespace Poco
{
template <class TArgs, class TStrategy, class TDelegate, class TMutex = FastMutex>
class AbstractEvent
/// An AbstractEvent is the base class of all events.
/// It works similar to the way C# handles notifications (aka events in C#).
///
/// Events can be used to send information to a set of delegates
/// which are registered with the event. The type of the data is specified with
/// the template parameter TArgs. The TStrategy parameter must be a subclass
/// of NotificationStrategy. The parameter TDelegate can either be a subclass of AbstractDelegate
/// or of AbstractPriorityDelegate.
///
/// Note that AbstractEvent should never be used directly. One ought to use
/// one of its subclasses which set the TStrategy and TDelegate template parameters
/// to fixed values. For most use-cases the BasicEvent template will be sufficient:
///
/// #include "Poco/BasicEvent.h"
/// #include "Poco/Delegate.h"
///
/// Note that as of release 1.4.2, the behavior of BasicEvent equals that of FIFOEvent,
/// so the FIFOEvent class is no longer necessary and provided for backwards compatibility
/// only.
///
/// BasicEvent works with a standard delegate. They allow one object to register
/// one or more delegates with an event. In contrast, a PriorityDelegate comes with an attached priority value
/// and allows one object to register for one priority value one or more delegates. Note that PriorityDelegates
/// only work with PriorityEvents:
///
/// #include "Poco/PriorityEvent.h"
/// #include "Poco/PriorityDelegate.h"
///
/// Use events by adding them as public members to the object which is throwing notifications:
///
/// class MyData
/// {
/// public:
/// Poco::BasicEvent<int> dataChanged;
///
/// MyData();
/// ...
/// void setData(int i);
/// ...
/// private:
/// int _data;
/// };
///
/// Firing the event is done either by calling the event's notify() or notifyAsync() method:
///
/// void MyData::setData(int i)
/// {
/// this->_data = i;
/// dataChanged.notify(this, this->_data);
/// }
///
/// Alternatively, instead of notify(), operator () can be used.
///
/// void MyData::setData(int i)
/// {
/// this->_data = i;
/// dataChanged(this, this->_data);
/// }
///
/// Note that operator (), notify() and notifyAsync() do not catch exceptions, i.e. in case a
/// delegate throws an exception, notifying is immediately aborted and the exception is propagated
/// back to the caller.
///
/// Delegates can register methods at the event. In the case of a BasicEvent
/// the Delegate template is used, in case of an PriorityEvent a PriorityDelegate is used.
/// Mixing of delegates, e.g. using a PriorityDelegate with a BasicEvent is not allowed and
/// can lead to compile-time and/or run-time errors. The standalone delegate() functions
/// can be used to construct Delegate objects.
///
/// Events require the observers to have one of the following method signatures:
///
/// void onEvent(const void* pSender, TArgs& args);
/// void onEvent(TArgs& args);
/// static void onEvent(const void* pSender, TArgs& args);
/// static void onEvent(void* pSender, TArgs& args);
/// static void onEvent(TArgs& args);
///
/// For performance reasons arguments are always sent by reference. This also allows observers
/// to modify the event argument. To prevent that, use <[const TArg]> as template
/// parameter. A non-conformant method signature leads to compile errors.
///
/// Assuming that the observer meets the method signature requirement, it can register
/// this method with the += operator:
///
/// class MyController
/// {
/// protected:
/// MyData _data;
///
/// void onDataChanged(void* pSender, int& data);
/// ...
/// };
///
/// MyController::MyController()
/// {
/// _data.dataChanged += delegate(this, &MyController::onDataChanged);
/// }
///
/// In some cases it might be desirable to work with automatically expiring registrations. Simply add
/// to delegate as 3rd parameter a expireValue (in milliseconds):
///
/// _data.dataChanged += delegate(this, &MyController::onDataChanged, 1000);
///
/// This will add a delegate to the event which will automatically be removed in 1000 millisecs.
///
/// Unregistering happens via the -= operator. Forgetting to unregister a method will lead to
/// segmentation faults later, when one tries to send a notify to a no longer existing object.
///
/// MyController::~MyController()
/// {
/// _data.dataChanged -= delegate(this, &MyController::onDataChanged);
/// }
///
/// Working with PriorityDelegate's as similar to working with BasicEvent.
/// Instead of delegate(), the priorityDelegate() function must be used
/// to create the PriorityDelegate.
{
public:
typedef TDelegate * DelegateHandle;
typedef TArgs Args;
AbstractEvent() : _executeAsync(this, &AbstractEvent::executeAsyncImpl), _enabled(true) { }
AbstractEvent(const TStrategy & strategy) : _executeAsync(this, &AbstractEvent::executeAsyncImpl), _strategy(strategy), _enabled(true)
{
}
virtual ~AbstractEvent() { }
void operator+=(const TDelegate & aDelegate)
/// Adds a delegate to the event.
///
/// Exact behavior is determined by the TStrategy.
{
typename TMutex::ScopedLock lock(_mutex);
_strategy.add(aDelegate);
}
void operator-=(const TDelegate & aDelegate)
/// Removes a delegate from the event.
///
/// If the delegate is not found, this function does nothing.
{
typename TMutex::ScopedLock lock(_mutex);
_strategy.remove(aDelegate);
}
DelegateHandle add(const TDelegate & aDelegate)
/// Adds a delegate to the event.
///
/// Exact behavior is determined by the TStrategy.
///
/// Returns a DelegateHandle which can be used in call to
/// remove() to remove the delegate.
{
typename TMutex::ScopedLock lock(_mutex);
return _strategy.add(aDelegate);
}
void remove(DelegateHandle delegateHandle)
/// Removes a delegate from the event using a DelegateHandle
/// returned by add().
///
/// If the delegate is not found, this function does nothing.
{
typename TMutex::ScopedLock lock(_mutex);
_strategy.remove(delegateHandle);
}
void operator()(const void * pSender, TArgs & args)
/// Shortcut for notify(pSender, args);
{
notify(pSender, args);
}
void operator()(TArgs & args)
/// Shortcut for notify(args).
{
notify(0, args);
}
void notify(const void * pSender, TArgs & args)
/// Sends a notification to all registered delegates. The order is
/// determined by the TStrategy. This method is blocking. While executing,
/// the list of delegates may be modified. These changes don't
/// influence the current active notifications but are activated with
/// the next notify. If a delegate is removed during a notify(), the
/// delegate will no longer be invoked (unless it has already been
/// invoked prior to removal). If one of the delegates throws an exception,
/// the notify method is immediately aborted and the exception is propagated
/// to the caller.
{
Poco::ScopedLockWithUnlock<TMutex> lock(_mutex);
if (!_enabled)
return;
// thread-safeness:
// copy should be faster and safer than blocking until
// execution ends
TStrategy strategy(_strategy);
lock.unlock();
strategy.notify(pSender, args);
}
bool hasDelegates() const { return !empty(); }
ActiveResult<TArgs> notifyAsync(const void * pSender, const TArgs & args)
/// Sends a notification to all registered delegates. The order is
/// determined by the TStrategy. This method is not blocking and will
/// immediately return. The delegates are invoked in a separate thread.
/// Call activeResult.wait() to wait until the notification has ended.
/// While executing, other objects can change the delegate list. These changes don't
/// influence the current active notifications but are activated with
/// the next notify. If a delegate is removed during a notify(), the
/// delegate will no longer be invoked (unless it has already been
/// invoked prior to removal). If one of the delegates throws an exception,
/// the execution is aborted and the exception is propagated to the caller.
{
NotifyAsyncParams params(pSender, args);
{
typename TMutex::ScopedLock lock(_mutex);
// thread-safeness:
// copy should be faster and safer than blocking until
// execution ends
// make a copy of the strategy here to guarantee that
// between notifyAsync and the execution of the method no changes can occur
params.ptrStrat = SharedPtr<TStrategy>(new TStrategy(_strategy));
params.enabled = _enabled;
}
ActiveResult<TArgs> result = _executeAsync(params);
return result;
}
void enable()
/// Enables the event.
{
typename TMutex::ScopedLock lock(_mutex);
_enabled = true;
}
void disable()
/// Disables the event. notify and notifyAsnyc will be ignored,
/// but adding/removing delegates is still allowed.
{
typename TMutex::ScopedLock lock(_mutex);
_enabled = false;
}
bool isEnabled() const
{
typename TMutex::ScopedLock lock(_mutex);
return _enabled;
}
void clear()
/// Removes all delegates.
{
typename TMutex::ScopedLock lock(_mutex);
_strategy.clear();
}
bool empty() const
/// Checks if any delegates are registered at the delegate.
{
typename TMutex::ScopedLock lock(_mutex);
return _strategy.empty();
}
protected:
struct NotifyAsyncParams
{
SharedPtr<TStrategy> ptrStrat;
const void * pSender;
TArgs args;
bool enabled;
NotifyAsyncParams(const void * pSend, const TArgs & a) : ptrStrat(), pSender(pSend), args(a), enabled(true)
/// Default constructor reduces the need for TArgs to have an empty constructor, only copy constructor is needed.
{
}
};
ActiveMethod<TArgs, NotifyAsyncParams, AbstractEvent> _executeAsync;
TArgs executeAsyncImpl(const NotifyAsyncParams & par)
{
if (!par.enabled)
{
return par.args;
}
NotifyAsyncParams params = par;
TArgs retArgs(params.args);
params.ptrStrat->notify(params.pSender, retArgs);
return retArgs;
}
TStrategy _strategy; /// The strategy used to notify observers.
bool _enabled; /// Stores if an event is enabled. Notfies on disabled events have no effect
/// but it is possible to change the observers.
mutable TMutex _mutex;
private:
AbstractEvent(const AbstractEvent & other);
AbstractEvent & operator=(const AbstractEvent & other);
};
template <class TStrategy, class TDelegate, class TMutex>
class AbstractEvent<void, TStrategy, TDelegate, TMutex>
{
public:
typedef TDelegate * DelegateHandle;
AbstractEvent() : _executeAsync(this, &AbstractEvent::executeAsyncImpl), _enabled(true) { }
AbstractEvent(const TStrategy & strategy) : _executeAsync(this, &AbstractEvent::executeAsyncImpl), _strategy(strategy), _enabled(true)
{
}
virtual ~AbstractEvent() { }
void operator+=(const TDelegate & aDelegate)
/// Adds a delegate to the event.
///
/// Exact behavior is determined by the TStrategy.
{
typename TMutex::ScopedLock lock(_mutex);
_strategy.add(aDelegate);
}
void operator-=(const TDelegate & aDelegate)
/// Removes a delegate from the event.
///
/// If the delegate is not found, this function does nothing.
{
typename TMutex::ScopedLock lock(_mutex);
_strategy.remove(aDelegate);
}
DelegateHandle add(const TDelegate & aDelegate)
/// Adds a delegate to the event.
///
/// Exact behavior is determined by the TStrategy.
///
/// Returns a DelegateHandle which can be used in call to
/// remove() to remove the delegate.
{
typename TMutex::ScopedLock lock(_mutex);
return _strategy.add(aDelegate);
}
void remove(DelegateHandle delegateHandle)
/// Removes a delegate from the event using a DelegateHandle
/// returned by add().
///
/// If the delegate is not found, this function does nothing.
{
typename TMutex::ScopedLock lock(_mutex);
_strategy.remove(delegateHandle);
}
void operator()(const void * pSender)
/// Shortcut for notify(pSender, args);
{
notify(pSender);
}
void operator()()
/// Shortcut for notify(args).
{
notify(0);
}
void notify(const void * pSender)
/// Sends a notification to all registered delegates. The order is
/// determined by the TStrategy. This method is blocking. While executing,
/// the list of delegates may be modified. These changes don't
/// influence the current active notifications but are activated with
/// the next notify. If a delegate is removed during a notify(), the
/// delegate will no longer be invoked (unless it has already been
/// invoked prior to removal). If one of the delegates throws an exception,
/// the notify method is immediately aborted and the exception is propagated
/// to the caller.
{
Poco::ScopedLockWithUnlock<TMutex> lock(_mutex);
if (!_enabled)
return;
// thread-safeness:
// copy should be faster and safer than blocking until
// execution ends
TStrategy strategy(_strategy);
lock.unlock();
strategy.notify(pSender);
}
ActiveResult<void> notifyAsync(const void * pSender)
/// Sends a notification to all registered delegates. The order is
/// determined by the TStrategy. This method is not blocking and will
/// immediately return. The delegates are invoked in a separate thread.
/// Call activeResult.wait() to wait until the notification has ended.
/// While executing, other objects can change the delegate list. These changes don't
/// influence the current active notifications but are activated with
/// the next notify. If a delegate is removed during a notify(), the
/// delegate will no longer be invoked (unless it has already been
/// invoked prior to removal). If one of the delegates throws an exception,
/// the execution is aborted and the exception is propagated to the caller.
{
NotifyAsyncParams params(pSender);
{
typename TMutex::ScopedLock lock(_mutex);
// thread-safeness:
// copy should be faster and safer than blocking until
// execution ends
// make a copy of the strategy here to guarantee that
// between notifyAsync and the execution of the method no changes can occur
params.ptrStrat = SharedPtr<TStrategy>(new TStrategy(_strategy));
params.enabled = _enabled;
}
ActiveResult<void> result = _executeAsync(params);
return result;
}
void enable()
/// Enables the event.
{
typename TMutex::ScopedLock lock(_mutex);
_enabled = true;
}
void disable()
/// Disables the event. notify and notifyAsnyc will be ignored,
/// but adding/removing delegates is still allowed.
{
typename TMutex::ScopedLock lock(_mutex);
_enabled = false;
}
bool isEnabled() const
{
typename TMutex::ScopedLock lock(_mutex);
return _enabled;
}
void clear()
/// Removes all delegates.
{
typename TMutex::ScopedLock lock(_mutex);
_strategy.clear();
}
bool empty() const
/// Checks if any delegates are registered at the delegate.
{
typename TMutex::ScopedLock lock(_mutex);
return _strategy.empty();
}
protected:
struct NotifyAsyncParams
{
SharedPtr<TStrategy> ptrStrat;
const void * pSender;
bool enabled;
NotifyAsyncParams(const void * pSend) : ptrStrat(), pSender(pSend), enabled(true)
/// Default constructor reduces the need for TArgs to have an empty constructor, only copy constructor is needed.
{
}
};
ActiveMethod<void, NotifyAsyncParams, AbstractEvent> _executeAsync;
void executeAsyncImpl(const NotifyAsyncParams & par)
{
if (!par.enabled)
{
return;
}
NotifyAsyncParams params = par;
params.ptrStrat->notify(params.pSender);
return;
}
TStrategy _strategy; /// The strategy used to notify observers.
bool _enabled; /// Stores if an event is enabled. Notfies on disabled events have no effect
/// but it is possible to change the observers.
mutable TMutex _mutex;
private:
AbstractEvent(const AbstractEvent & other);
AbstractEvent & operator=(const AbstractEvent & other);
};
} // namespace Poco
#endif // Foundation_AbstractFoundation_INCLUDED