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-rw-r--r--dom/bindings/Nullable.h140
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diff --git a/dom/bindings/Nullable.h b/dom/bindings/Nullable.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/. */
+
+#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 */