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// Copyright 2016 PDFium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CORE_FXCRT_OBSERVABLE_H_
#define CORE_FXCRT_OBSERVABLE_H_
#include <set>
#include "core/fxcrt/fx_system.h"
#include "third_party/base/stl_util.h"
namespace fxcrt {
template <class T>
class Observable {
public:
// General-purpose interface for more complicated cleanup.
class Observer {
public:
virtual ~Observer() = default;
virtual void OnObservableDestroyed() = 0;
};
// Simple case of a self-nulling pointer.
class ObservedPtr final : public Observer {
public:
ObservedPtr() = default;
explicit ObservedPtr(T* pObservable) : m_pObservable(pObservable) {
if (m_pObservable)
m_pObservable->AddObserver(this);
}
ObservedPtr(const ObservedPtr& that) : ObservedPtr(that.Get()) {}
~ObservedPtr() override {
if (m_pObservable)
m_pObservable->RemoveObserver(this);
}
void Reset(T* pObservable = nullptr) {
if (m_pObservable)
m_pObservable->RemoveObserver(this);
m_pObservable = pObservable;
if (m_pObservable)
m_pObservable->AddObserver(this);
}
void OnObservableDestroyed() override {
ASSERT(m_pObservable);
m_pObservable = nullptr;
}
ObservedPtr& operator=(const ObservedPtr& that) {
Reset(that.Get());
return *this;
}
bool operator==(const ObservedPtr& that) const {
return m_pObservable == that.m_pObservable;
}
bool operator!=(const ObservedPtr& that) const { return !(*this == that); }
explicit operator bool() const { return !!m_pObservable; }
T* Get() const { return m_pObservable; }
T& operator*() const { return *m_pObservable; }
T* operator->() const { return m_pObservable; }
private:
T* m_pObservable = nullptr;
};
Observable() = default;
Observable(const Observable& that) = delete;
~Observable() { NotifyObservers(); }
void AddObserver(Observer* pObserver) {
ASSERT(!pdfium::ContainsKey(m_Observers, pObserver));
m_Observers.insert(pObserver);
}
void RemoveObserver(Observer* pObserver) {
ASSERT(pdfium::ContainsKey(m_Observers, pObserver));
m_Observers.erase(pObserver);
}
void NotifyObservers() {
for (auto* pObserver : m_Observers)
pObserver->OnObservableDestroyed();
m_Observers.clear();
}
Observable& operator=(const Observable& that) = delete;
protected:
size_t ActiveObserversForTesting() const { return m_Observers.size(); }
private:
std::set<Observer*> m_Observers;
};
} // namespace fxcrt
using fxcrt::Observable;
#endif // CORE_FXCRT_OBSERVABLE_H_
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