1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/mfbt/TypedEnum.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,282 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim: set ts=8 sts=2 et sw=2 tw=80: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +/* Macros to emulate C++11 typed enums and enum classes. */
1.11 +
1.12 +#ifndef mozilla_TypedEnum_h
1.13 +#define mozilla_TypedEnum_h
1.14 +
1.15 +#include "mozilla/TypedEnumInternal.h"
1.16 +#include "mozilla/MacroArgs.h"
1.17 +
1.18 +#if defined(__cplusplus)
1.19 +
1.20 +/**
1.21 + * MOZ_ENUM_TYPE specifies the underlying numeric type for an enum. It's
1.22 + * specified by placing MOZ_ENUM_TYPE(type) immediately after the enum name in
1.23 + * its declaration, and before the opening curly brace, like
1.24 + *
1.25 + * enum MyEnum MOZ_ENUM_TYPE(uint16_t)
1.26 + * {
1.27 + * A,
1.28 + * B = 7,
1.29 + * C
1.30 + * };
1.31 + *
1.32 + * In supporting compilers, the macro will expand to ": uint16_t". The
1.33 + * compiler will allocate exactly two bytes for MyEnum and will require all
1.34 + * enumerators to have values between 0 and 65535. (Thus specifying "B =
1.35 + * 100000" instead of "B = 7" would fail to compile.) In old compilers the
1.36 + * macro expands to the empty string, and the underlying type is generally
1.37 + * undefined.
1.38 + */
1.39 +#ifdef MOZ_HAVE_CXX11_ENUM_TYPE
1.40 +# define MOZ_ENUM_TYPE(type) : type
1.41 +#else
1.42 +# define MOZ_ENUM_TYPE(type) /* no support */
1.43 +#endif
1.44 +
1.45 +/**
1.46 + * MOZ_BEGIN_ENUM_CLASS and MOZ_END_ENUM_CLASS provide access to the
1.47 + * strongly-typed enumeration feature of C++11 ("enum class"). If supported
1.48 + * by the compiler, an enum defined using these macros will not be implicitly
1.49 + * converted to any other type, and its enumerators will be scoped using the
1.50 + * enumeration name. Place MOZ_BEGIN_ENUM_CLASS(EnumName [, type]) in place of
1.51 + * "enum EnumName {", and MOZ_END_ENUM_CLASS(EnumName) in place of the closing
1.52 + * "};". For example,
1.53 + *
1.54 + * MOZ_BEGIN_ENUM_CLASS(Enum, int32_t)
1.55 + * A,
1.56 + * B = 6
1.57 + * MOZ_END_ENUM_CLASS(Enum)
1.58 + *
1.59 + * This will make "Enum::A" and "Enum::B" appear in the global scope, but "A"
1.60 + * and "B" will not. In compilers that support C++11 strongly-typed
1.61 + * enumerations, implicit conversions of Enum values to numeric types will
1.62 + * fail. In other compilers, Enum itself will actually be defined as a class,
1.63 + * and some implicit conversions will fail while others will succeed.
1.64 + *
1.65 + * The optional type argument specifies the underlying type for the enum where
1.66 + * supported, as with MOZ_ENUM_TYPE(). As with MOZ_ENUM_TYPE(), it will do
1.67 + * nothing on compilers that do not support it.
1.68 + *
1.69 + * MOZ_{BEGIN,END}_ENUM_CLASS doesn't work for defining enum classes nested
1.70 + * inside classes. To define an enum class nested inside another class, use
1.71 + * MOZ_{BEGIN,END}_NESTED_ENUM_CLASS, and place a MOZ_FINISH_NESTED_ENUM_CLASS
1.72 + * in namespace scope to handle bits that can only be implemented with
1.73 + * namespace-scoped code. For example:
1.74 + *
1.75 + * class FooBar {
1.76 + *
1.77 + * MOZ_BEGIN_NESTED_ENUM_CLASS(Enum, int32_t)
1.78 + * A,
1.79 + * B = 6
1.80 + * MOZ_END_NESTED_ENUM_CLASS(Enum)
1.81 + *
1.82 + * };
1.83 + *
1.84 + * MOZ_FINISH_NESTED_ENUM_CLASS(FooBar::Enum)
1.85 + */
1.86 +#if defined(MOZ_HAVE_CXX11_STRONG_ENUMS)
1.87 + /*
1.88 + * All compilers that support strong enums also support an explicit
1.89 + * underlying type, so no extra check is needed.
1.90 + */
1.91 +
1.92 + /* Single-argument form. */
1.93 +# define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER1(Name) \
1.94 + enum class Name {
1.95 + /* Two-argument form. */
1.96 +# define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER2(Name, type) \
1.97 + enum class Name : type {
1.98 +# define MOZ_END_NESTED_ENUM_CLASS(Name) \
1.99 + };
1.100 +# define MOZ_FINISH_NESTED_ENUM_CLASS(Name) /* nothing */
1.101 +
1.102 + /*
1.103 + * MOZ_ENUM_CLASS_ENUM_TYPE allows using enum classes
1.104 + * as template parameter types. For that, we need integer types.
1.105 + * In the present case where the compiler supports strong enums,
1.106 + * these are already integer types so there is nothing more to do.
1.107 + */
1.108 +# define MOZ_ENUM_CLASS_ENUM_TYPE(Name) Name
1.109 + /*
1.110 + * See the comment below about MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE.
1.111 + */
1.112 +# define MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE(Name) Name
1.113 +#else
1.114 + /**
1.115 + * We need Name to both name a type, and scope the provided enumerator
1.116 + * names. Namespaces and classes both provide scoping, but namespaces
1.117 + * aren't types, so we need to use a class that wraps the enum values. We
1.118 + * have an implicit conversion from the inner enum type to the class, so
1.119 + * statements like
1.120 + *
1.121 + * Enum x = Enum::A;
1.122 + *
1.123 + * will still work. We need to define an implicit conversion from the class
1.124 + * to the inner enum as well, so that (for instance) switch statements will
1.125 + * work. This means that the class can be implicitly converted to a numeric
1.126 + * value as well via the enum type, since C++ allows an implicit
1.127 + * user-defined conversion followed by a standard conversion to still be
1.128 + * implicit.
1.129 + *
1.130 + * We have an explicit constructor from int defined, so that casts like
1.131 + * (Enum)7 will still work. We also have a zero-argument constructor with
1.132 + * no arguments, so declaration without initialization (like "Enum foo;")
1.133 + * will work.
1.134 + *
1.135 + * Additionally, we'll delete as many operators as possible for the inner
1.136 + * enum type, so statements like this will still fail:
1.137 + *
1.138 + * f(5 + Enum::B); // deleted operator+
1.139 + *
1.140 + * But we can't prevent things like this, because C++ doesn't allow
1.141 + * overriding conversions or assignment operators for enums:
1.142 + *
1.143 + * int x = Enum::A;
1.144 + * int f()
1.145 + * {
1.146 + * return Enum::A;
1.147 + * }
1.148 + */
1.149 +
1.150 + /* Single-argument form. */
1.151 +# define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER1(Name) \
1.152 + class Name \
1.153 + { \
1.154 + public: \
1.155 + enum Enum \
1.156 + {
1.157 + /* Two-argument form. */
1.158 +# define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER2(Name, type) \
1.159 + class Name \
1.160 + { \
1.161 + public: \
1.162 + enum Enum MOZ_ENUM_TYPE(type) \
1.163 + {
1.164 +# define MOZ_END_NESTED_ENUM_CLASS(Name) \
1.165 + }; \
1.166 + Name() {} \
1.167 + MOZ_CONSTEXPR Name(Enum aEnum) : mEnum(aEnum) {} \
1.168 + template<typename Other> \
1.169 + explicit MOZ_CONSTEXPR Name(Other num) : mEnum((Enum)num) {} \
1.170 + MOZ_CONSTEXPR operator Enum() const { return mEnum; } \
1.171 + explicit MOZ_CONSTEXPR Name(const mozilla::CastableTypedEnumResult<Name>& aOther) \
1.172 + : mEnum(aOther.get()) \
1.173 + {} \
1.174 + private: \
1.175 + Enum mEnum; \
1.176 + };
1.177 +# define MOZ_FINISH_NESTED_ENUM_CLASS(Name) \
1.178 + inline int operator+(const int&, const Name::Enum&) MOZ_DELETE; \
1.179 + inline int operator+(const Name::Enum&, const int&) MOZ_DELETE; \
1.180 + inline int operator-(const int&, const Name::Enum&) MOZ_DELETE; \
1.181 + inline int operator-(const Name::Enum&, const int&) MOZ_DELETE; \
1.182 + inline int operator*(const int&, const Name::Enum&) MOZ_DELETE; \
1.183 + inline int operator*(const Name::Enum&, const int&) MOZ_DELETE; \
1.184 + inline int operator/(const int&, const Name::Enum&) MOZ_DELETE; \
1.185 + inline int operator/(const Name::Enum&, const int&) MOZ_DELETE; \
1.186 + inline int operator%(const int&, const Name::Enum&) MOZ_DELETE; \
1.187 + inline int operator%(const Name::Enum&, const int&) MOZ_DELETE; \
1.188 + inline int operator+(const Name::Enum&) MOZ_DELETE; \
1.189 + inline int operator-(const Name::Enum&) MOZ_DELETE; \
1.190 + inline int& operator++(Name::Enum&) MOZ_DELETE; \
1.191 + inline int operator++(Name::Enum&, int) MOZ_DELETE; \
1.192 + inline int& operator--(Name::Enum&) MOZ_DELETE; \
1.193 + inline int operator--(Name::Enum&, int) MOZ_DELETE; \
1.194 + inline bool operator==(const int&, const Name::Enum&) MOZ_DELETE; \
1.195 + inline bool operator==(const Name::Enum&, const int&) MOZ_DELETE; \
1.196 + inline bool operator!=(const int&, const Name::Enum&) MOZ_DELETE; \
1.197 + inline bool operator!=(const Name::Enum&, const int&) MOZ_DELETE; \
1.198 + inline bool operator>(const int&, const Name::Enum&) MOZ_DELETE; \
1.199 + inline bool operator>(const Name::Enum&, const int&) MOZ_DELETE; \
1.200 + inline bool operator<(const int&, const Name::Enum&) MOZ_DELETE; \
1.201 + inline bool operator<(const Name::Enum&, const int&) MOZ_DELETE; \
1.202 + inline bool operator>=(const int&, const Name::Enum&) MOZ_DELETE; \
1.203 + inline bool operator>=(const Name::Enum&, const int&) MOZ_DELETE; \
1.204 + inline bool operator<=(const int&, const Name::Enum&) MOZ_DELETE; \
1.205 + inline bool operator<=(const Name::Enum&, const int&) MOZ_DELETE; \
1.206 + inline bool operator!(const Name::Enum&) MOZ_DELETE; \
1.207 + inline bool operator&&(const bool&, const Name::Enum&) MOZ_DELETE; \
1.208 + inline bool operator&&(const Name::Enum&, const bool&) MOZ_DELETE; \
1.209 + inline bool operator||(const bool&, const Name::Enum&) MOZ_DELETE; \
1.210 + inline bool operator||(const Name::Enum&, const bool&) MOZ_DELETE; \
1.211 + inline int operator&(const int&, const Name::Enum&) MOZ_DELETE; \
1.212 + inline int operator&(const Name::Enum&, const int&) MOZ_DELETE; \
1.213 + inline int operator|(const int&, const Name::Enum&) MOZ_DELETE; \
1.214 + inline int operator|(const Name::Enum&, const int&) MOZ_DELETE; \
1.215 + inline int operator^(const int&, const Name::Enum&) MOZ_DELETE; \
1.216 + inline int operator^(const Name::Enum&, const int&) MOZ_DELETE; \
1.217 + inline int operator<<(const int&, const Name::Enum&) MOZ_DELETE; \
1.218 + inline int operator<<(const Name::Enum&, const int&) MOZ_DELETE; \
1.219 + inline int operator>>(const int&, const Name::Enum&) MOZ_DELETE; \
1.220 + inline int operator>>(const Name::Enum&, const int&) MOZ_DELETE; \
1.221 + inline int& operator+=(int&, const Name::Enum&) MOZ_DELETE; \
1.222 + inline int& operator-=(int&, const Name::Enum&) MOZ_DELETE; \
1.223 + inline int& operator*=(int&, const Name::Enum&) MOZ_DELETE; \
1.224 + inline int& operator/=(int&, const Name::Enum&) MOZ_DELETE; \
1.225 + inline int& operator%=(int&, const Name::Enum&) MOZ_DELETE; \
1.226 + inline int& operator&=(int&, const Name::Enum&) MOZ_DELETE; \
1.227 + inline int& operator|=(int&, const Name::Enum&) MOZ_DELETE; \
1.228 + inline int& operator^=(int&, const Name::Enum&) MOZ_DELETE; \
1.229 + inline int& operator<<=(int&, const Name::Enum&) MOZ_DELETE; \
1.230 + inline int& operator>>=(int&, const Name::Enum&) MOZ_DELETE;
1.231 +
1.232 + /*
1.233 + * MOZ_ENUM_CLASS_ENUM_TYPE allows using enum classes
1.234 + * as template parameter types. For that, we need integer types.
1.235 + * In the present case, the integer type is the Enum nested type.
1.236 + */
1.237 +# define MOZ_ENUM_CLASS_ENUM_TYPE(Name) Name::Enum
1.238 + /*
1.239 + * MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE is a variant of MOZ_ENUM_CLASS_ENUM_TYPE
1.240 + * to be used when the enum class at hand depends on template parameters.
1.241 + *
1.242 + * Indeed, if T depends on template parameters, in order to name a nested type
1.243 + * in T, C++ does not allow to just write "T::NestedType". Instead, we have
1.244 + * to write "typename T::NestedType". The role of this macro is to add
1.245 + * this "typename" keywords where needed.
1.246 + *
1.247 + * Example:
1.248 + *
1.249 + * template<typename T, MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE(T) Value>
1.250 + * struct S {};
1.251 + *
1.252 + * MOZ_BEGIN_ENUM_CLASS(E)
1.253 + * Foo,
1.254 + * Bar
1.255 + * MOZ_END_ENUM_CLASS(E)
1.256 + *
1.257 + * S<E, E::Bar> s;
1.258 + *
1.259 + * In this example, the second template parameter to S is meant to be of type T,
1.260 + * but on non-C++11 compilers, type T is a class type, not an integer type, so
1.261 + * it is not accepted as the type of a constant template parameter. One would
1.262 + * then want to use MOZ_ENUM_CLASS_ENUM_TYPE(T), but that doesn't work either
1.263 + * as T depends on template parameters (more specifically here, T _is_ a template
1.264 + * parameter) so as MOZ_ENUM_CLASS_ENUM_TYPE(T) expands to T::Enum, we are missing
1.265 + * the required "typename" keyword. So here, MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE
1.266 + * is needed.
1.267 + */
1.268 +# define MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE(Name) typename Name::Enum
1.269 +#endif
1.270 +
1.271 +# define MOZ_BEGIN_NESTED_ENUM_CLASS_GLUE(a, b) a b
1.272 +# define MOZ_BEGIN_NESTED_ENUM_CLASS(...) \
1.273 + MOZ_BEGIN_NESTED_ENUM_CLASS_GLUE( \
1.274 + MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER, \
1.275 + __VA_ARGS__), \
1.276 + (__VA_ARGS__))
1.277 +
1.278 +# define MOZ_BEGIN_ENUM_CLASS(...) MOZ_BEGIN_NESTED_ENUM_CLASS(__VA_ARGS__)
1.279 +# define MOZ_END_ENUM_CLASS(Name) \
1.280 + MOZ_END_NESTED_ENUM_CLASS(Name) \
1.281 + MOZ_FINISH_NESTED_ENUM_CLASS(Name)
1.282 +
1.283 +#endif /* __cplusplus */
1.284 +
1.285 +#endif /* mozilla_TypedEnum_h */
