зеркало из https://github.com/mozilla/gecko-dev.git
93 строки
2.8 KiB
C++
93 строки
2.8 KiB
C++
/* -*- 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
|