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