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124 lines
2.5 KiB
C++
124 lines
2.5 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_dom_Nullable_h
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#define mozilla_dom_Nullable_h
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#include "mozilla/Assertions.h"
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#include "nsTArrayForwardDeclare.h"
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#include "mozilla/Move.h"
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#include "mozilla/Maybe.h"
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class nsCycleCollectionTraversalCallback;
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namespace mozilla {
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namespace dom {
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// Support for nullable types
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template <typename T>
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struct Nullable
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{
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private:
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Maybe<T> mValue;
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public:
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Nullable()
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: mValue()
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{}
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explicit Nullable(T aValue)
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: mValue()
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{
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mValue.emplace(aValue);
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}
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explicit Nullable(Nullable<T>&& aOther)
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: mValue(mozilla::Move(aOther.mValue))
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{}
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Nullable(const Nullable<T>& aOther)
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: mValue(aOther.mValue)
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{}
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void operator=(const Nullable<T>& aOther)
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{
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mValue = aOther.mValue;
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}
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void SetValue(T aValue) {
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mValue.reset();
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mValue.emplace(aValue);
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}
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// For cases when |T| is some type with nontrivial copy behavior, we may want
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// to get a reference to our internal copy of T and work with it directly
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// instead of relying on the copying version of SetValue().
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T& SetValue() {
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if (mValue.isNothing()) {
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mValue.emplace();
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}
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return mValue.ref();
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}
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void SetNull() {
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mValue.reset();
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}
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const T& Value() const {
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return mValue.ref();
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}
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T& Value() {
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return mValue.ref();
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}
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bool IsNull() const {
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return mValue.isNothing();
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}
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bool Equals(const Nullable<T>& aOtherNullable) const
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{
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return mValue == aOtherNullable.mValue;
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}
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bool operator==(const Nullable<T>& aOtherNullable) const
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{
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return Equals(aOtherNullable);
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}
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bool operator!=(const Nullable<T>& aOtherNullable) const
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{
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return !Equals(aOtherNullable);
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}
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};
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template<typename T>
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void
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ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
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Nullable<T>& aNullable,
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const char* aName,
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uint32_t aFlags = 0)
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{
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if (!aNullable.IsNull()) {
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ImplCycleCollectionTraverse(aCallback, aNullable.Value(), aName, aFlags);
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}
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}
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template<typename T>
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void
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ImplCycleCollectionUnlink(Nullable<T>& aNullable)
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{
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if (!aNullable.IsNull()) {
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ImplCycleCollectionUnlink(aNullable.Value());
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}
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}
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} // namespace dom
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} // namespace mozilla
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#endif /* mozilla_dom_Nullable_h */
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