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/* -*- 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/. */
// A wrapper that uses RAII to ensure that a class invariant is checked
// before and after any public function is called
#ifndef CHECKINVARIANTWRAPPER_H_
#define CHECKINVARIANTWRAPPER_H_
#include "mozilla/Attributes.h"
#include <utility>
namespace mozilla {
//
// Wraps an object of type T and allows access to its public API by
// deferencing it using the pointer syntax "->".
//
// Using that operator will return a temporary RAII object that
// calls a method named "CheckInvariant" in its constructor, calls the
// requested method, and then calls "CheckInvariant" again in its
// destructor.
//
// The only thing your class requires is a method with the following signature:
//
// void CheckInvariant() const;
//
template <typename T>
class CheckInvariantWrapper {
public:
class Wrapper {
public:
explicit Wrapper(T& aObject) : mObject(aObject) {
mObject.CheckInvariant();
}
~Wrapper() { mObject.CheckInvariant(); }
T* operator->() { return &mObject; }
private:
T& mObject;
};
class ConstWrapper {
public:
explicit ConstWrapper(const T& aObject) : mObject(aObject) {
mObject.CheckInvariant();
}
~ConstWrapper() { mObject.CheckInvariant(); }
const T* operator->() const { return &mObject; }
private:
const T& mObject;
};
CheckInvariantWrapper() = default;
MOZ_IMPLICIT CheckInvariantWrapper(T aObject) : mObject(std::move(aObject)) {}
template <typename... Args>
explicit CheckInvariantWrapper(std::in_place_t, Args&&... args)
: mObject(std::forward<Args>(args)...) {}
const ConstWrapper operator->() const { return ConstWrapper(mObject); }
Wrapper operator->() { return Wrapper(mObject); }
private:
T mObject;
};
} // namespace mozilla
#endif // CHECKINVARIANTWRAPPER_H_
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