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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_OBSERVED_PTR_H_
#define CORE_FXCRT_OBSERVED_PTR_H_
#include <stddef.h>
#include <set>
#include "third_party/base/check.h"
namespace fxcrt {
class Observable {
public:
// General-purpose interface for more complicated cleanup.
class ObserverIface {
public:
virtual ~ObserverIface() = default;
virtual void OnObservableDestroyed() = 0;
};
Observable();
Observable(const Observable& that) = delete;
Observable& operator=(const Observable& that) = delete;
~Observable();
void AddObserver(ObserverIface* pObserver);
void RemoveObserver(ObserverIface* pObserver);
void NotifyObservers();
protected:
size_t ActiveObserversForTesting() const { return m_Observers.size(); }
private:
std::set<ObserverIface*> m_Observers;
};
// Simple case of a self-nulling pointer.
template <typename T>
class ObservedPtr final : public Observable::ObserverIface {
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 {
DCHECK(m_pObservable);
m_pObservable = nullptr;
}
bool HasObservable() const { return !!m_pObservable; }
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); }
template <typename U>
bool operator==(const U* that) const {
return Get() == that;
}
template <typename U>
bool operator!=(const U* that) const {
return !(*this == that);
}
explicit operator bool() const { return HasObservable(); }
T* Get() const { return m_pObservable; }
T& operator*() const { return *m_pObservable; }
T* operator->() const { return m_pObservable; }
private:
T* m_pObservable = nullptr;
};
template <typename T, typename U>
inline bool operator==(const U* lhs, const ObservedPtr<T>& rhs) {
return rhs == lhs;
}
template <typename T, typename U>
inline bool operator!=(const U* lhs, const ObservedPtr<T>& rhs) {
return rhs != lhs;
}
} // namespace fxcrt
using fxcrt::Observable;
using fxcrt::ObservedPtr;
#endif // CORE_FXCRT_OBSERVED_PTR_H_