/* -*- 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/. */ /* Macros to emulate C++11 typed enums and enum classes. */ #ifndef mozilla_TypedEnum_h #define mozilla_TypedEnum_h #include "mozilla/TypedEnumInternal.h" #include "mozilla/MacroArgs.h" #if defined(__cplusplus) /** * MOZ_ENUM_TYPE specifies the underlying numeric type for an enum. It's * specified by placing MOZ_ENUM_TYPE(type) immediately after the enum name in * its declaration, and before the opening curly brace, like * * enum MyEnum MOZ_ENUM_TYPE(uint16_t) * { * A, * B = 7, * C * }; * * In supporting compilers, the macro will expand to ": uint16_t". The * compiler will allocate exactly two bytes for MyEnum and will require all * enumerators to have values between 0 and 65535. (Thus specifying "B = * 100000" instead of "B = 7" would fail to compile.) In old compilers the * macro expands to the empty string, and the underlying type is generally * undefined. */ #ifdef MOZ_HAVE_CXX11_ENUM_TYPE # define MOZ_ENUM_TYPE(type) : type #else # define MOZ_ENUM_TYPE(type) /* no support */ #endif /** * MOZ_BEGIN_ENUM_CLASS and MOZ_END_ENUM_CLASS provide access to the * strongly-typed enumeration feature of C++11 ("enum class"). If supported * by the compiler, an enum defined using these macros will not be implicitly * converted to any other type, and its enumerators will be scoped using the * enumeration name. Place MOZ_BEGIN_ENUM_CLASS(EnumName [, type]) in place of * "enum EnumName {", and MOZ_END_ENUM_CLASS(EnumName) in place of the closing * "};". For example, * * MOZ_BEGIN_ENUM_CLASS(Enum, int32_t) * A, * B = 6 * MOZ_END_ENUM_CLASS(Enum) * * This will make "Enum::A" and "Enum::B" appear in the global scope, but "A" * and "B" will not. In compilers that support C++11 strongly-typed * enumerations, implicit conversions of Enum values to numeric types will * fail. In other compilers, Enum itself will actually be defined as a class, * and some implicit conversions will fail while others will succeed. * * The optional type argument specifies the underlying type for the enum where * supported, as with MOZ_ENUM_TYPE(). As with MOZ_ENUM_TYPE(), it will do * nothing on compilers that do not support it. * * MOZ_{BEGIN,END}_ENUM_CLASS doesn't work for defining enum classes nested * inside classes. To define an enum class nested inside another class, use * MOZ_{BEGIN,END}_NESTED_ENUM_CLASS, and place a MOZ_FINISH_NESTED_ENUM_CLASS * in namespace scope to handle bits that can only be implemented with * namespace-scoped code. For example: * * class FooBar * { * MOZ_BEGIN_NESTED_ENUM_CLASS(Enum, int32_t) * A, * B = 6 * MOZ_END_NESTED_ENUM_CLASS(Enum) * }; * * MOZ_FINISH_NESTED_ENUM_CLASS(FooBar::Enum) */ #if defined(MOZ_HAVE_CXX11_STRONG_ENUMS) /* * All compilers that support strong enums also support an explicit * underlying type, so no extra check is needed. */ /* Single-argument form. */ # define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER1(Name) \ enum class Name { /* Two-argument form. */ # define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER2(Name, type) \ enum class Name : type { # define MOZ_END_NESTED_ENUM_CLASS(Name) \ }; # define MOZ_FINISH_NESTED_ENUM_CLASS(Name) /* nothing */ /* * MOZ_ENUM_CLASS_ENUM_TYPE allows using enum classes * as template parameter types. For that, we need integer types. * In the present case where the compiler supports strong enums, * these are already integer types so there is nothing more to do. */ # define MOZ_ENUM_CLASS_ENUM_TYPE(Name) Name /* * See the comment below about MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE. */ # define MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE(Name) Name #else /** * We need Name to both name a type, and scope the provided enumerator * names. Namespaces and classes both provide scoping, but namespaces * aren't types, so we need to use a class that wraps the enum values. We * have an implicit conversion from the inner enum type to the class, so * statements like * * Enum x = Enum::A; * * will still work. We need to define an implicit conversion from the class * to the inner enum as well, so that (for instance) switch statements will * work. This means that the class can be implicitly converted to a numeric * value as well via the enum type, since C++ allows an implicit * user-defined conversion followed by a standard conversion to still be * implicit. * * We have an explicit constructor from int defined, so that casts like * (Enum)7 will still work. We also have a zero-argument constructor with * no arguments, so declaration without initialization (like "Enum foo;") * will work. * * Additionally, we'll delete as many operators as possible for the inner * enum type, so statements like this will still fail: * * f(5 + Enum::B); // deleted operator+ * * But we can't prevent things like this, because C++ doesn't allow * overriding conversions or assignment operators for enums: * * int x = Enum::A; * int f() * { * return Enum::A; * } */ /* Single-argument form. */ # define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER1(Name) \ class Name \ { \ public: \ enum Enum \ { /* Two-argument form. */ # define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER2(Name, type) \ class Name \ { \ public: \ enum Enum MOZ_ENUM_TYPE(type) \ { # define MOZ_END_NESTED_ENUM_CLASS(Name) \ }; \ Name() {} \ MOZ_CONSTEXPR Name(Enum aEnum) : mEnum(aEnum) {} \ template \ explicit MOZ_CONSTEXPR Name(Other num) : mEnum((Enum)num) {} \ MOZ_CONSTEXPR operator Enum() const { return mEnum; } \ explicit MOZ_CONSTEXPR Name(const mozilla::CastableTypedEnumResult& aOther) \ : mEnum(aOther.get()) \ {} \ private: \ Enum mEnum; \ }; # define MOZ_FINISH_NESTED_ENUM_CLASS(Name) \ inline int operator+(const int&, const Name::Enum&) = delete; \ inline int operator+(const Name::Enum&, const int&) = delete; \ inline int operator-(const int&, const Name::Enum&) = delete; \ inline int operator-(const Name::Enum&, const int&) = delete; \ inline int operator*(const int&, const Name::Enum&) = delete; \ inline int operator*(const Name::Enum&, const int&) = delete; \ inline int operator/(const int&, const Name::Enum&) = delete; \ inline int operator/(const Name::Enum&, const int&) = delete; \ inline int operator%(const int&, const Name::Enum&) = delete; \ inline int operator%(const Name::Enum&, const int&) = delete; \ inline int operator+(const Name::Enum&) = delete; \ inline int operator-(const Name::Enum&) = delete; \ inline int& operator++(Name::Enum&) = delete; \ inline int operator++(Name::Enum&, int) = delete; \ inline int& operator--(Name::Enum&) = delete; \ inline int operator--(Name::Enum&, int) = delete; \ inline bool operator==(const int&, const Name::Enum&) = delete; \ inline bool operator==(const Name::Enum&, const int&) = delete; \ inline bool operator!=(const int&, const Name::Enum&) = delete; \ inline bool operator!=(const Name::Enum&, const int&) = delete; \ inline bool operator>(const int&, const Name::Enum&) = delete; \ inline bool operator>(const Name::Enum&, const int&) = delete; \ inline bool operator<(const int&, const Name::Enum&) = delete; \ inline bool operator<(const Name::Enum&, const int&) = delete; \ inline bool operator>=(const int&, const Name::Enum&) = delete; \ inline bool operator>=(const Name::Enum&, const int&) = delete; \ inline bool operator<=(const int&, const Name::Enum&) = delete; \ inline bool operator<=(const Name::Enum&, const int&) = delete; \ inline bool operator!(const Name::Enum&) = delete; \ inline bool operator&&(const bool&, const Name::Enum&) = delete; \ inline bool operator&&(const Name::Enum&, const bool&) = delete; \ inline bool operator||(const bool&, const Name::Enum&) = delete; \ inline bool operator||(const Name::Enum&, const bool&) = delete; \ inline int operator&(const int&, const Name::Enum&) = delete; \ inline int operator&(const Name::Enum&, const int&) = delete; \ inline int operator|(const int&, const Name::Enum&) = delete; \ inline int operator|(const Name::Enum&, const int&) = delete; \ inline int operator^(const int&, const Name::Enum&) = delete; \ inline int operator^(const Name::Enum&, const int&) = delete; \ inline int operator<<(const int&, const Name::Enum&) = delete; \ inline int operator<<(const Name::Enum&, const int&) = delete; \ inline int operator>>(const int&, const Name::Enum&) = delete; \ inline int operator>>(const Name::Enum&, const int&) = delete; \ inline int& operator+=(int&, const Name::Enum&) = delete; \ inline int& operator-=(int&, const Name::Enum&) = delete; \ inline int& operator*=(int&, const Name::Enum&) = delete; \ inline int& operator/=(int&, const Name::Enum&) = delete; \ inline int& operator%=(int&, const Name::Enum&) = delete; \ inline int& operator&=(int&, const Name::Enum&) = delete; \ inline int& operator|=(int&, const Name::Enum&) = delete; \ inline int& operator^=(int&, const Name::Enum&) = delete; \ inline int& operator<<=(int&, const Name::Enum&) = delete; \ inline int& operator>>=(int&, const Name::Enum&) = delete; /* * MOZ_ENUM_CLASS_ENUM_TYPE allows using enum classes * as template parameter types. For that, we need integer types. * In the present case, the integer type is the Enum nested type. */ # define MOZ_ENUM_CLASS_ENUM_TYPE(Name) Name::Enum /* * MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE is a variant of MOZ_ENUM_CLASS_ENUM_TYPE * to be used when the enum class at hand depends on template parameters. * * Indeed, if T depends on template parameters, in order to name a nested type * in T, C++ does not allow to just write "T::NestedType". Instead, we have * to write "typename T::NestedType". The role of this macro is to add * this "typename" keywords where needed. * * Example: * * template * struct S {}; * * MOZ_BEGIN_ENUM_CLASS(E) * Foo, * Bar * MOZ_END_ENUM_CLASS(E) * * S s; * * In this example, the second template parameter to S is meant to be of type * T, but on non-C++11 compilers, type T is a class type, not an integer * type, so it is not accepted as the type of a constant template parameter. * One would then want to use MOZ_ENUM_CLASS_ENUM_TYPE(T), but that doesn't * work either as T depends on template parameters (more specifically here, T * _is_ a template parameter) so as MOZ_ENUM_CLASS_ENUM_TYPE(T) expands to * T::Enum, we are missing the required "typename" keyword. So here, * MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE is needed. */ # define MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE(Name) typename Name::Enum #endif # define MOZ_BEGIN_NESTED_ENUM_CLASS_GLUE(a, b) a b # define MOZ_BEGIN_NESTED_ENUM_CLASS(...) \ MOZ_BEGIN_NESTED_ENUM_CLASS_GLUE( \ MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER, \ __VA_ARGS__), \ (__VA_ARGS__)) # define MOZ_BEGIN_ENUM_CLASS(...) MOZ_BEGIN_NESTED_ENUM_CLASS(__VA_ARGS__) # define MOZ_END_ENUM_CLASS(Name) \ MOZ_END_NESTED_ENUM_CLASS(Name) \ MOZ_FINISH_NESTED_ENUM_CLASS(Name) #endif /* __cplusplus */ #endif /* mozilla_TypedEnum_h */