mirror of
https://github.com/mozilla/gecko-dev.git
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93 lines
2.8 KiB
C++
93 lines
2.8 KiB
C++
/* -*- Mode: C++; tab-width: 2; 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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/* Internal storage class used e.g. by Maybe and Result. This file doesn't
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* contain any public declarations. */
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#ifndef mfbt_MaybeStorageBase_h
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#define mfbt_MaybeStorageBase_h
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#include <type_traits>
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#include <utility>
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namespace mozilla::detail {
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template <typename T>
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constexpr bool IsTriviallyDestructibleAndCopyable =
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std::is_trivially_destructible_v<T> &&
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(std::is_trivially_copy_constructible_v<T> ||
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!std::is_copy_constructible_v<T>);
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template <typename T, bool TriviallyDestructibleAndCopyable =
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IsTriviallyDestructibleAndCopyable<T>>
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struct MaybeStorageBase;
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template <typename T>
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struct MaybeStorageBase<T, false> {
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protected:
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using NonConstT = std::remove_const_t<T>;
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union Union {
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Union() {}
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explicit Union(const T& aVal) : val{aVal} {}
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template <typename U,
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typename = std::enable_if_t<std::is_move_constructible_v<U>>>
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explicit Union(U&& aVal) : val{std::forward<U>(aVal)} {}
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template <typename... Args>
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explicit Union(std::in_place_t, Args&&... aArgs)
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: val{std::forward<Args>(aArgs)...} {}
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~Union() {}
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NonConstT val;
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} mStorage;
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public:
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MaybeStorageBase() = default;
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explicit MaybeStorageBase(const T& aVal) : mStorage{aVal} {}
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explicit MaybeStorageBase(T&& aVal) : mStorage{std::move(aVal)} {}
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template <typename... Args>
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explicit MaybeStorageBase(std::in_place_t, Args&&... aArgs)
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: mStorage{std::in_place, std::forward<Args>(aArgs)...} {}
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const T* addr() const { return &mStorage.val; }
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T* addr() { return &mStorage.val; }
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};
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template <typename T>
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struct MaybeStorageBase<T, true> {
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protected:
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using NonConstT = std::remove_const_t<T>;
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union Union {
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constexpr Union() : dummy() {}
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constexpr explicit Union(const T& aVal) : val{aVal} {}
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constexpr explicit Union(T&& aVal) : val{std::move(aVal)} {}
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template <typename... Args>
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constexpr explicit Union(std::in_place_t, Args&&... aArgs)
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: val{std::forward<Args>(aArgs)...} {}
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NonConstT val;
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char dummy;
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} mStorage;
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public:
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constexpr MaybeStorageBase() = default;
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constexpr explicit MaybeStorageBase(const T& aVal) : mStorage{aVal} {}
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constexpr explicit MaybeStorageBase(T&& aVal) : mStorage{std::move(aVal)} {}
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template <typename... Args>
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constexpr explicit MaybeStorageBase(std::in_place_t, Args&&... aArgs)
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: mStorage{std::in_place, std::forward<Args>(aArgs)...} {}
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constexpr const T* addr() const { return &mStorage.val; }
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constexpr T* addr() { return &mStorage.val; }
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};
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} // namespace mozilla::detail
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#endif
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