mirror of
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214 lines
9.3 KiB
C++
214 lines
9.3 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* Macros to emulate C++11 typed enums and enum classes. */
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#ifndef mozilla_TypedEnum_h_
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#define mozilla_TypedEnum_h_
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#include "mozilla/Attributes.h"
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#if defined(__cplusplus)
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#if defined(__clang__)
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/*
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* Per Clang documentation, "Note that marketing version numbers should not
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* be used to check for language features, as different vendors use different
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* numbering schemes. Instead, use the feature checking macros."
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*/
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# ifndef __has_extension
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# define __has_extension __has_feature /* compatibility, for older versions of clang */
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# endif
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# if __has_extension(cxx_strong_enums)
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# define MOZ_HAVE_CXX11_ENUM_TYPE
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# define MOZ_HAVE_CXX11_STRONG_ENUMS
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# endif
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#elif defined(__GNUC__)
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# if defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L
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# if MOZ_GCC_VERSION_AT_LEAST(4, 5, 1)
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# define MOZ_HAVE_CXX11_ENUM_TYPE
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# define MOZ_HAVE_CXX11_STRONG_ENUMS
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# endif
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# endif
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#elif defined(_MSC_VER)
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# if _MSC_VER >= 1400
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# define MOZ_HAVE_CXX11_ENUM_TYPE
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# endif
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# if _MSC_VER >= 1700
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# define MOZ_HAVE_CXX11_STRONG_ENUMS
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# endif
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#endif
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/**
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* MOZ_ENUM_TYPE specifies the underlying numeric type for an enum. It's
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* specified by placing MOZ_ENUM_TYPE(type) immediately after the enum name in
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* its declaration, and before the opening curly brace, like
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*
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* enum MyEnum MOZ_ENUM_TYPE(uint16_t)
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* {
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* A,
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* B = 7,
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* C
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* };
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*
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* In supporting compilers, the macro will expand to ": uint16_t". The
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* compiler will allocate exactly two bytes for MyEnum and will require all
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* enumerators to have values between 0 and 65535. (Thus specifying "B =
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* 100000" instead of "B = 7" would fail to compile.) In old compilers the
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* macro expands to the empty string, and the underlying type is generally
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* undefined.
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*/
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#ifdef MOZ_HAVE_CXX11_ENUM_TYPE
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# define MOZ_ENUM_TYPE(type) : type
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#else
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# define MOZ_ENUM_TYPE(type) /* no support */
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#endif
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/**
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* MOZ_BEGIN_ENUM_CLASS and MOZ_END_ENUM_CLASS provide access to the
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* strongly-typed enumeration feature of C++11 ("enum class"). If supported
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* by the compiler, an enum defined using these macros will not be implicitly
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* converted to any other type, and its enumerators will be scoped using the
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* enumeration name. Place MOZ_BEGIN_ENUM_CLASS(EnumName, type) in place of
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* "enum EnumName {", and MOZ_END_ENUM_CLASS(EnumName) in place of the closing
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* "};". For example,
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*
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* MOZ_BEGIN_ENUM_CLASS(Enum, int32_t)
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* A,
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* B = 6
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* MOZ_END_ENUM_CLASS(Enum)
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*
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* This will make "Enum::A" and "Enum::B" appear in the global scope, but "A"
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* and "B" will not. In compilers that support C++11 strongly-typed
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* enumerations, implicit conversions of Enum values to numeric types will
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* fail. In other compilers, Enum itself will actually be defined as a class,
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* and some implicit conversions will fail while others will succeed.
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*
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* The type argument specifies the underlying type for the enum where
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* supported, as with MOZ_ENUM_TYPE(). For simplicity, it is currently
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* mandatory. As with MOZ_ENUM_TYPE(), it will do nothing on compilers that do
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* not support it.
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*
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* Note that the workaround implemented here is not compatible with enums
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* nested inside a class.
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*/
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#if defined(MOZ_HAVE_CXX11_STRONG_ENUMS)
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/*
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* All compilers that support strong enums also support an explicit
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* underlying type, so no extra check is needed.
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*/
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# define MOZ_BEGIN_ENUM_CLASS(Name, type) enum class Name : type {
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# define MOZ_END_ENUM_CLASS(Name) };
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#else
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/**
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* We need Name to both name a type, and scope the provided enumerator
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* names. Namespaces and classes both provide scoping, but namespaces
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* aren't types, so we need to use a class that wraps the enum values. We
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* have an implicit conversion from the inner enum type to the class, so
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* statements like
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*
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* Enum x = Enum::A;
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*
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* will still work. We need to define an implicit conversion from the class
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* to the inner enum as well, so that (for instance) switch statements will
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* work. This means that the class can be implicitly converted to a numeric
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* value as well via the enum type, since C++ allows an implicit
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* user-defined conversion followed by a standard conversion to still be
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* implicit.
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*
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* We have an explicit constructor from int defined, so that casts like
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* (Enum)7 will still work. We also have a zero-argument constructor with
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* no arguments, so declaration without initialization (like "Enum foo;")
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* will work.
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*
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* Additionally, we'll delete as many operators as possible for the inner
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* enum type, so statements like this will still fail:
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*
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* f(5 + Enum::B); // deleted operator+
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*
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* But we can't prevent things like this, because C++ doesn't allow
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* overriding conversions or assignment operators for enums:
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*
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* int x = Enum::A;
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* int f()
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* {
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* return Enum::A;
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* }
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*/
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# define MOZ_BEGIN_ENUM_CLASS(Name, type) \
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class Name \
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{ \
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public: \
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enum Enum MOZ_ENUM_TYPE(type) \
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{
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# define MOZ_END_ENUM_CLASS(Name) \
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}; \
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Name() {} \
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Name(Enum aEnum) : mEnum(aEnum) {} \
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explicit Name(int num) : mEnum((Enum)num) {} \
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operator Enum() const { return mEnum; } \
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private: \
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Enum mEnum; \
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}; \
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inline int operator+(const int&, const Name::Enum&) MOZ_DELETE; \
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inline int operator+(const Name::Enum&, const int&) MOZ_DELETE; \
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inline int operator-(const int&, const Name::Enum&) MOZ_DELETE; \
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inline int operator-(const Name::Enum&, const int&) MOZ_DELETE; \
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inline int operator*(const int&, const Name::Enum&) MOZ_DELETE; \
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inline int operator*(const Name::Enum&, const int&) MOZ_DELETE; \
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inline int operator/(const int&, const Name::Enum&) MOZ_DELETE; \
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inline int operator/(const Name::Enum&, const int&) MOZ_DELETE; \
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inline int operator%(const int&, const Name::Enum&) MOZ_DELETE; \
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inline int operator%(const Name::Enum&, const int&) MOZ_DELETE; \
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inline int operator+(const Name::Enum&) MOZ_DELETE; \
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inline int operator-(const Name::Enum&) MOZ_DELETE; \
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inline int& operator++(Name::Enum&) MOZ_DELETE; \
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inline int operator++(Name::Enum&, int) MOZ_DELETE; \
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inline int& operator--(Name::Enum&) MOZ_DELETE; \
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inline int operator--(Name::Enum&, int) MOZ_DELETE; \
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inline bool operator==(const int&, const Name::Enum&) MOZ_DELETE; \
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inline bool operator==(const Name::Enum&, const int&) MOZ_DELETE; \
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inline bool operator!=(const int&, const Name::Enum&) MOZ_DELETE; \
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inline bool operator!=(const Name::Enum&, const int&) MOZ_DELETE; \
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inline bool operator>(const int&, const Name::Enum&) MOZ_DELETE; \
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inline bool operator>(const Name::Enum&, const int&) MOZ_DELETE; \
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inline bool operator<(const int&, const Name::Enum&) MOZ_DELETE; \
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inline bool operator<(const Name::Enum&, const int&) MOZ_DELETE; \
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inline bool operator>=(const int&, const Name::Enum&) MOZ_DELETE; \
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inline bool operator>=(const Name::Enum&, const int&) MOZ_DELETE; \
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inline bool operator<=(const int&, const Name::Enum&) MOZ_DELETE; \
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inline bool operator<=(const Name::Enum&, const int&) MOZ_DELETE; \
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inline bool operator!(const Name::Enum&) MOZ_DELETE; \
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inline bool operator&&(const bool&, const Name::Enum&) MOZ_DELETE; \
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inline bool operator&&(const Name::Enum&, const bool&) MOZ_DELETE; \
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inline bool operator||(const bool&, const Name::Enum&) MOZ_DELETE; \
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inline bool operator||(const Name::Enum&, const bool&) MOZ_DELETE; \
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inline int operator~(const Name::Enum&) MOZ_DELETE; \
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inline int operator&(const int&, const Name::Enum&) MOZ_DELETE; \
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inline int operator&(const Name::Enum&, const int&) MOZ_DELETE; \
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inline int operator|(const int&, const Name::Enum&) MOZ_DELETE; \
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inline int operator|(const Name::Enum&, const int&) MOZ_DELETE; \
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inline int operator^(const int&, const Name::Enum&) MOZ_DELETE; \
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inline int operator^(const Name::Enum&, const int&) MOZ_DELETE; \
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inline int operator<<(const int&, const Name::Enum&) MOZ_DELETE; \
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inline int operator<<(const Name::Enum&, const int&) MOZ_DELETE; \
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inline int operator>>(const int&, const Name::Enum&) MOZ_DELETE; \
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inline int operator>>(const Name::Enum&, const int&) MOZ_DELETE; \
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inline int& operator+=(int&, const Name::Enum&) MOZ_DELETE; \
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inline int& operator-=(int&, const Name::Enum&) MOZ_DELETE; \
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inline int& operator*=(int&, const Name::Enum&) MOZ_DELETE; \
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inline int& operator/=(int&, const Name::Enum&) MOZ_DELETE; \
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inline int& operator%=(int&, const Name::Enum&) MOZ_DELETE; \
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inline int& operator&=(int&, const Name::Enum&) MOZ_DELETE; \
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inline int& operator|=(int&, const Name::Enum&) MOZ_DELETE; \
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inline int& operator^=(int&, const Name::Enum&) MOZ_DELETE; \
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inline int& operator<<=(int&, const Name::Enum&) MOZ_DELETE; \
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inline int& operator>>=(int&, const Name::Enum&) MOZ_DELETE;
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#endif
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#endif /* __cplusplus */
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#endif /* mozilla_TypedEnum_h_ */
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