mirror of
https://github.com/mozilla/gecko-dev.git
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282 lines
12 KiB
C++
282 lines
12 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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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/TypedEnumInternal.h"
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#include "mozilla/MacroArgs.h"
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#if defined(__cplusplus)
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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 optional type argument specifies the underlying type for the enum where
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* supported, as with MOZ_ENUM_TYPE(). As with MOZ_ENUM_TYPE(), it will do
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* nothing on compilers that do not support it.
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*
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* MOZ_{BEGIN,END}_ENUM_CLASS doesn't work for defining enum classes nested
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* inside classes. To define an enum class nested inside another class, use
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* MOZ_{BEGIN,END}_NESTED_ENUM_CLASS, and place a MOZ_FINISH_NESTED_ENUM_CLASS
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* in namespace scope to handle bits that can only be implemented with
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* namespace-scoped code. For example:
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*
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* class FooBar
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* {
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* MOZ_BEGIN_NESTED_ENUM_CLASS(Enum, int32_t)
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* A,
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* B = 6
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* MOZ_END_NESTED_ENUM_CLASS(Enum)
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* };
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*
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* MOZ_FINISH_NESTED_ENUM_CLASS(FooBar::Enum)
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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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/* Single-argument form. */
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# define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER1(Name) \
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enum class Name {
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/* Two-argument form. */
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# define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER2(Name, type) \
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enum class Name : type {
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# define MOZ_END_NESTED_ENUM_CLASS(Name) \
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};
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# define MOZ_FINISH_NESTED_ENUM_CLASS(Name) /* nothing */
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/*
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* MOZ_ENUM_CLASS_ENUM_TYPE allows using enum classes
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* as template parameter types. For that, we need integer types.
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* In the present case where the compiler supports strong enums,
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* these are already integer types so there is nothing more to do.
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*/
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# define MOZ_ENUM_CLASS_ENUM_TYPE(Name) Name
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/*
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* See the comment below about MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE.
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*/
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# define MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE(Name) 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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/* Single-argument form. */
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# define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER1(Name) \
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class Name \
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{ \
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public: \
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enum Enum \
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{
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/* Two-argument form. */
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# define MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER2(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_NESTED_ENUM_CLASS(Name) \
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}; \
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Name() {} \
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MOZ_CONSTEXPR Name(Enum aEnum) : mEnum(aEnum) {} \
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template<typename Other> \
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explicit MOZ_CONSTEXPR Name(Other num) : mEnum((Enum)num) {} \
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MOZ_CONSTEXPR operator Enum() const { return mEnum; } \
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explicit MOZ_CONSTEXPR Name(const mozilla::CastableTypedEnumResult<Name>& aOther) \
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: mEnum(aOther.get()) \
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{} \
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private: \
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Enum mEnum; \
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};
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# define MOZ_FINISH_NESTED_ENUM_CLASS(Name) \
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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 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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/*
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* MOZ_ENUM_CLASS_ENUM_TYPE allows using enum classes
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* as template parameter types. For that, we need integer types.
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* In the present case, the integer type is the Enum nested type.
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*/
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# define MOZ_ENUM_CLASS_ENUM_TYPE(Name) Name::Enum
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/*
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* MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE is a variant of MOZ_ENUM_CLASS_ENUM_TYPE
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* to be used when the enum class at hand depends on template parameters.
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*
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* Indeed, if T depends on template parameters, in order to name a nested type
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* in T, C++ does not allow to just write "T::NestedType". Instead, we have
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* to write "typename T::NestedType". The role of this macro is to add
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* this "typename" keywords where needed.
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*
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* Example:
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*
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* template<typename T, MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE(T) Value>
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* struct S {};
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*
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* MOZ_BEGIN_ENUM_CLASS(E)
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* Foo,
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* Bar
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* MOZ_END_ENUM_CLASS(E)
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*
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* S<E, E::Bar> s;
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*
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* In this example, the second template parameter to S is meant to be of type
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* T, but on non-C++11 compilers, type T is a class type, not an integer
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* type, so it is not accepted as the type of a constant template parameter.
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* One would then want to use MOZ_ENUM_CLASS_ENUM_TYPE(T), but that doesn't
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* work either as T depends on template parameters (more specifically here, T
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* _is_ a template parameter) so as MOZ_ENUM_CLASS_ENUM_TYPE(T) expands to
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* T::Enum, we are missing the required "typename" keyword. So here,
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* MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE is needed.
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*/
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# define MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE(Name) typename Name::Enum
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#endif
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# define MOZ_BEGIN_NESTED_ENUM_CLASS_GLUE(a, b) a b
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# define MOZ_BEGIN_NESTED_ENUM_CLASS(...) \
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MOZ_BEGIN_NESTED_ENUM_CLASS_GLUE( \
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MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_BEGIN_NESTED_ENUM_CLASS_HELPER, \
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__VA_ARGS__), \
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(__VA_ARGS__))
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# define MOZ_BEGIN_ENUM_CLASS(...) MOZ_BEGIN_NESTED_ENUM_CLASS(__VA_ARGS__)
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# define MOZ_END_ENUM_CLASS(Name) \
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MOZ_END_NESTED_ENUM_CLASS(Name) \
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MOZ_FINISH_NESTED_ENUM_CLASS(Name)
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#endif /* __cplusplus */
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#endif /* mozilla_TypedEnum_h */
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