b66e7f947b
Also useful for bug 1775062. Differential Revision: https://phabricator.services.mozilla.com/D152740
46 lines
1.4 KiB
C++
46 lines
1.4 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
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* A class for holding the members of a union. */
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#ifndef mozilla_dom_UnionMember_h
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#define mozilla_dom_UnionMember_h
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#include "mozilla/Alignment.h"
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#include "mozilla/Attributes.h"
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#include <utility>
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namespace mozilla::dom {
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// The union type has an enum to keep track of which of its UnionMembers has
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// been constructed.
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template <class T>
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class UnionMember {
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AlignedStorage2<T> mStorage;
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// Copy construction can't be supported because C++ requires that any enclosed
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// T be initialized in a way C++ knows about -- that is, by |new| or similar.
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UnionMember(const UnionMember&) = delete;
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public:
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UnionMember() = default;
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~UnionMember() = default;
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template <typename... Args>
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T& SetValue(Args&&... args) {
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new (mStorage.addr()) T(std::forward<Args>(args)...);
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return *mStorage.addr();
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}
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T& Value() { return *mStorage.addr(); }
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const T& Value() const { return *mStorage.addr(); }
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void Destroy() { mStorage.addr()->~T(); }
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} MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS;
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} // namespace mozilla::dom
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#endif // mozilla_dom_UnionMember_h
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