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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
commit | 6bf0a5cb5034a7e684dcc3500e841785237ce2dd (patch) | |
tree | a68f146d7fa01f0134297619fbe7e33db084e0aa /mfbt/TypedEnumBits.h | |
parent | Initial commit. (diff) | |
download | thunderbird-6bf0a5cb5034a7e684dcc3500e841785237ce2dd.tar.xz thunderbird-6bf0a5cb5034a7e684dcc3500e841785237ce2dd.zip |
Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | mfbt/TypedEnumBits.h | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/mfbt/TypedEnumBits.h b/mfbt/TypedEnumBits.h new file mode 100644 index 0000000000..b431d90e02 --- /dev/null +++ b/mfbt/TypedEnumBits.h @@ -0,0 +1,135 @@ +/* -*- Mode: C++; tab-width: 8; 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/. */ + +/* + * MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS allows using a typed enum as bit flags. + */ + +#ifndef mozilla_TypedEnumBits_h +#define mozilla_TypedEnumBits_h + +#include "mozilla/Attributes.h" +#include "mozilla/IntegerTypeTraits.h" + +namespace mozilla { + +/* + * The problem that CastableTypedEnumResult aims to solve is that + * typed enums are not convertible to bool, and there is no way to make them + * be, yet user code wants to be able to write + * + * if (myFlags & Flags::SOME_PARTICULAR_FLAG) (1) + * + * There are different approaches to solving this. Most of them require + * adapting user code. For example, we could implement operator! and have + * the user write + * + * if (!!(myFlags & Flags::SOME_PARTICULAR_FLAG)) (2) + * + * Or we could supply a IsNonZero() or Any() function returning whether + * an enum value is nonzero, and have the user write + * + * if (Any(Flags & Flags::SOME_PARTICULAR_FLAG)) (3) + * + * But instead, we choose to preserve the original user syntax (1) as it + * is inherently more readable, and to ease porting existing code to typed + * enums. We achieve this by having operator& and other binary bitwise + * operators have as return type a class, CastableTypedEnumResult, + * that wraps a typed enum but adds bool convertibility. + */ +template <typename E> +class CastableTypedEnumResult { + private: + const E mValue; + + public: + explicit constexpr CastableTypedEnumResult(E aValue) : mValue(aValue) {} + + constexpr operator E() const { return mValue; } + + template <typename DestinationType> + explicit constexpr operator DestinationType() const { + return DestinationType(mValue); + } + + constexpr bool operator!() const { return !bool(mValue); } +}; + +#define MOZ_CASTABLETYPEDENUMRESULT_BINOP(Op, OtherType, ReturnType) \ + template <typename E> \ + constexpr ReturnType operator Op(const OtherType& aE, \ + const CastableTypedEnumResult<E>& aR) { \ + return ReturnType(aE Op OtherType(aR)); \ + } \ + template <typename E> \ + constexpr ReturnType operator Op(const CastableTypedEnumResult<E>& aR, \ + const OtherType& aE) { \ + return ReturnType(OtherType(aR) Op aE); \ + } \ + template <typename E> \ + constexpr ReturnType operator Op(const CastableTypedEnumResult<E>& aR1, \ + const CastableTypedEnumResult<E>& aR2) { \ + return ReturnType(OtherType(aR1) Op OtherType(aR2)); \ + } + +MOZ_CASTABLETYPEDENUMRESULT_BINOP(|, E, CastableTypedEnumResult<E>) +MOZ_CASTABLETYPEDENUMRESULT_BINOP(&, E, CastableTypedEnumResult<E>) +MOZ_CASTABLETYPEDENUMRESULT_BINOP(^, E, CastableTypedEnumResult<E>) +MOZ_CASTABLETYPEDENUMRESULT_BINOP(==, E, bool) +MOZ_CASTABLETYPEDENUMRESULT_BINOP(!=, E, bool) + +template <typename E> +constexpr CastableTypedEnumResult<E> operator~( + const CastableTypedEnumResult<E>& aR) { + return CastableTypedEnumResult<E>(~(E(aR))); +} + +#define MOZ_CASTABLETYPEDENUMRESULT_COMPOUND_ASSIGN_OP(Op) \ + template <typename E> \ + E& operator Op(E& aR1, const CastableTypedEnumResult<E>& aR2) { \ + return aR1 Op E(aR2); \ + } + +MOZ_CASTABLETYPEDENUMRESULT_COMPOUND_ASSIGN_OP(&=) +MOZ_CASTABLETYPEDENUMRESULT_COMPOUND_ASSIGN_OP(|=) +MOZ_CASTABLETYPEDENUMRESULT_COMPOUND_ASSIGN_OP(^=) + +#undef MOZ_CASTABLETYPEDENUMRESULT_COMPOUND_ASSIGN_OP + +#undef MOZ_CASTABLETYPEDENUMRESULT_BINOP + +namespace detail { +template <typename E> +struct UnsignedIntegerTypeForEnum : UnsignedStdintTypeForSize<sizeof(E)> {}; +} // namespace detail + +} // namespace mozilla + +#define MOZ_MAKE_ENUM_CLASS_BINOP_IMPL(Name, Op) \ + inline constexpr mozilla::CastableTypedEnumResult<Name> operator Op( \ + Name a, Name b) { \ + typedef mozilla::CastableTypedEnumResult<Name> Result; \ + typedef mozilla::detail::UnsignedIntegerTypeForEnum<Name>::Type U; \ + return Result(Name(U(a) Op U(b))); \ + } \ + \ + inline Name& operator Op##=(Name& a, Name b) { return a = a Op b; } + +/** + * MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS generates standard bitwise operators + * for the given enum type. Use this to enable using an enum type as bit-field. + */ +#define MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(Name) \ + MOZ_MAKE_ENUM_CLASS_BINOP_IMPL(Name, |) \ + MOZ_MAKE_ENUM_CLASS_BINOP_IMPL(Name, &) \ + MOZ_MAKE_ENUM_CLASS_BINOP_IMPL(Name, ^) \ + inline constexpr mozilla::CastableTypedEnumResult<Name> operator~(Name a) { \ + typedef mozilla::CastableTypedEnumResult<Name> Result; \ + typedef mozilla::detail::UnsignedIntegerTypeForEnum<Name>::Type U; \ + return Result(Name(~(U(a)))); \ + } + +#endif // mozilla_TypedEnumBits_h |