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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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_dom_Nullable_h
#define mozilla_dom_Nullable_h
#include "mozilla/Assertions.h"
#include "nsTArrayForwardDeclare.h"
#include "mozilla/Move.h"
#include "mozilla/Maybe.h"
class nsCycleCollectionTraversalCallback;
namespace mozilla {
namespace dom {
// Support for nullable types
template <typename T>
struct Nullable
{
private:
Maybe<T> mValue;
public:
Nullable()
: mValue()
{}
MOZ_IMPLICIT Nullable(const decltype(nullptr)&)
: mValue()
{}
explicit Nullable(const T& aValue)
: mValue()
{
mValue.emplace(aValue);
}
MOZ_IMPLICIT Nullable(T&& aValue)
: mValue()
{
mValue.emplace(mozilla::Move(aValue));
}
Nullable(Nullable<T>&& aOther)
: mValue(mozilla::Move(aOther.mValue))
{}
Nullable(const Nullable<T>& aOther)
: mValue(aOther.mValue)
{}
void operator=(const Nullable<T>& aOther)
{
mValue = aOther.mValue;
}
void SetValue(const T& aArgs)
{
mValue.reset();
mValue.emplace(aArgs);
}
void SetValue(T&& aArgs)
{
mValue.reset();
mValue.emplace(mozilla::Move(aArgs));
}
// For cases when |T| is some type with nontrivial copy behavior, we may want
// to get a reference to our internal copy of T and work with it directly
// instead of relying on the copying version of SetValue().
T& SetValue() {
if (mValue.isNothing()) {
mValue.emplace();
}
return mValue.ref();
}
void SetNull() {
mValue.reset();
}
const T& Value() const {
return mValue.ref();
}
T& Value() {
return mValue.ref();
}
bool IsNull() const {
return mValue.isNothing();
}
bool Equals(const Nullable<T>& aOtherNullable) const
{
return mValue == aOtherNullable.mValue;
}
bool operator==(const Nullable<T>& aOtherNullable) const
{
return Equals(aOtherNullable);
}
bool operator!=(const Nullable<T>& aOtherNullable) const
{
return !Equals(aOtherNullable);
}
};
template<typename T>
void
ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
Nullable<T>& aNullable,
const char* aName,
uint32_t aFlags = 0)
{
if (!aNullable.IsNull()) {
ImplCycleCollectionTraverse(aCallback, aNullable.Value(), aName, aFlags);
}
}
template<typename T>
void
ImplCycleCollectionUnlink(Nullable<T>& aNullable)
{
if (!aNullable.IsNull()) {
ImplCycleCollectionUnlink(aNullable.Value());
}
}
} // namespace dom
} // namespace mozilla
#endif /* mozilla_dom_Nullable_h */
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