gecko-dev/dom/bindings/OwningNonNull.h

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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 class for non-null strong pointers to reference-counted objects. */
#ifndef mozilla_dom_OwningNonNull_h
#define mozilla_dom_OwningNonNull_h
#include "nsAutoPtr.h"
#include "nsCycleCollectionNoteChild.h"
namespace mozilla {
namespace dom {
template<class T>
class OwningNonNull
{
public:
OwningNonNull()
#ifdef DEBUG
: mInited(false)
#endif
{}
// This is no worse than get() in terms of const handling.
operator T&() const
{
MOZ_ASSERT(mInited);
MOZ_ASSERT(mPtr, "OwningNonNull<T> was set to null");
return *mPtr;
}
operator T*() const
{
MOZ_ASSERT(mInited);
MOZ_ASSERT(mPtr, "OwningNonNull<T> was set to null");
return mPtr;
}
void operator=(T* aValue)
{
init(aValue);
}
void operator=(T& aValue)
{
init(&aValue);
}
void operator=(const already_AddRefed<T>& aValue)
{
init(aValue);
}
already_AddRefed<T> forget()
{
#ifdef DEBUG
mInited = false;
#endif
return mPtr.forget();
}
// Make us work with smart pointer helpers that expect a get().
T* get() const
{
MOZ_ASSERT(mInited);
MOZ_ASSERT(mPtr);
return mPtr;
}
protected:
template<typename U>
void init(U aValue)
{
mPtr = aValue;
MOZ_ASSERT(mPtr);
#ifdef DEBUG
mInited = true;
#endif
}
nsRefPtr<T> mPtr;
#ifdef DEBUG
bool mInited;
#endif
};
template <typename T>
inline void
ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
OwningNonNull<T>& aField,
const char* aName,
uint32_t aFlags = 0)
{
CycleCollectionNoteChild(aCallback, aField.get(), aName, aFlags);
}
} // namespace dom
} // namespace mozilla
#endif // mozilla_dom_OwningNonNull_h