gecko-dev/xpcom/ds/Observer.h
Gabriele Svelto 2d99f56b0e Bug 1469914 - Prevent the HAL from registering duplicate observers; r=froydnj
This also replaces the custom logic in ObserverList with an nsTObserverArray
which has all the necessary logic for stable iteration over a potentially
changing list of items. Unused dependencies were also removed.

--HG--
extra : source : 303478f7f248470a1c747f42dad9cb85c3129f0a
2018-06-22 00:35:08 +02:00

87 lines
2.0 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */
#ifndef mozilla_Observer_h
#define mozilla_Observer_h
#include "nsTObserverArray.h"
namespace mozilla {
/**
* Observer<T> provides a way for a class to observe something.
* When an event has to be broadcasted to all Observer<T>, Notify() method
* is called.
* T represents the type of the object passed in argument to Notify().
*
* @see ObserverList.
*/
template<class T>
class Observer
{
public:
virtual ~Observer() {}
virtual void Notify(const T& aParam) = 0;
};
/**
* ObserverList<T> tracks Observer<T> and can notify them when Broadcast() is
* called.
* T represents the type of the object passed in argument to Broadcast() and
* sent to Observer<T> objects through Notify().
*
* @see Observer.
*/
template<class T>
class ObserverList
{
public:
/**
* Note: When calling AddObserver, it's up to the caller to make sure the
* object isn't going to be release as long as RemoveObserver hasn't been
* called.
*
* @see RemoveObserver()
*/
void AddObserver(Observer<T>* aObserver)
{
mObservers.AppendElementUnlessExists(aObserver);
}
/**
* Remove the observer from the observer list.
* @return Whether the observer has been found in the list.
*/
bool RemoveObserver(Observer<T>* aObserver)
{
return mObservers.RemoveElement(aObserver);
}
uint32_t Length()
{
return mObservers.Length();
}
/**
* Call Notify() on each item in the list.
*/
void Broadcast(const T& aParam)
{
typename nsTObserverArray<Observer<T>*>::ForwardIterator iter(mObservers);
while (iter.HasMore()) {
Observer<T>* obs = iter.GetNext();
obs->Notify(aParam);
}
}
protected:
nsTObserverArray<Observer<T>*> mObservers;
};
} // namespace mozilla
#endif // mozilla_Observer_h