/* -*- 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/. */ #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 */