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 /* -*- 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<typename Other> \

          explicit MOZ_CONSTEXPR Name(Other num) : mEnum((Enum)num) {} \

          MOZ_CONSTEXPR operator Enum() const { return mEnum; } \

          explicit MOZ_CONSTEXPR Name(const mozilla::CastableTypedEnumResult<Name>& aOther) \

            : mEnum(aOther.get()) \

          {} \

        private: \

          Enum mEnum; \

      };

 #  define MOZ_FINISH_NESTED_ENUM_CLASS(Name) \

      inline int operator+(const int&, const Name::Enum&) MOZ_DELETE; \

      inline int operator+(const Name::Enum&, const int&) MOZ_DELETE; \

      inline int operator-(const int&, const Name::Enum&) MOZ_DELETE; \

      inline int operator-(const Name::Enum&, const int&) MOZ_DELETE; \

      inline int operator*(const int&, const Name::Enum&) MOZ_DELETE; \

      inline int operator*(const Name::Enum&, const int&) MOZ_DELETE; \

      inline int operator/(const int&, const Name::Enum&) MOZ_DELETE; \

      inline int operator/(const Name::Enum&, const int&) MOZ_DELETE; \

      inline int operator%(const int&, const Name::Enum&) MOZ_DELETE; \

      inline int operator%(const Name::Enum&, const int&) MOZ_DELETE; \

      inline int operator+(const Name::Enum&) MOZ_DELETE; \

      inline int operator-(const Name::Enum&) MOZ_DELETE; \

      inline int& operator++(Name::Enum&) MOZ_DELETE; \

      inline int operator++(Name::Enum&, int) MOZ_DELETE; \

      inline int& operator--(Name::Enum&) MOZ_DELETE; \

      inline int operator--(Name::Enum&, int) MOZ_DELETE; \

      inline bool operator==(const int&, const Name::Enum&) MOZ_DELETE; \

      inline bool operator==(const Name::Enum&, const int&) MOZ_DELETE; \

      inline bool operator!=(const int&, const Name::Enum&) MOZ_DELETE; \

      inline bool operator!=(const Name::Enum&, const int&) MOZ_DELETE; \

      inline bool operator>(const int&, const Name::Enum&) MOZ_DELETE; \

      inline bool operator>(const Name::Enum&, const int&) MOZ_DELETE; \

      inline bool operator<(const int&, const Name::Enum&) MOZ_DELETE; \

      inline bool operator<(const Name::Enum&, const int&) MOZ_DELETE; \

      inline bool operator>=(const int&, const Name::Enum&) MOZ_DELETE; \

      inline bool operator>=(const Name::Enum&, const int&) MOZ_DELETE; \

      inline bool operator<=(const int&, const Name::Enum&) MOZ_DELETE; \

      inline bool operator<=(const Name::Enum&, const int&) MOZ_DELETE; \

      inline bool operator!(const Name::Enum&) MOZ_DELETE; \

      inline bool operator&&(const bool&, const Name::Enum&) MOZ_DELETE; \

      inline bool operator&&(const Name::Enum&, const bool&) MOZ_DELETE; \

      inline bool operator||(const bool&, const Name::Enum&) MOZ_DELETE; \

      inline bool operator||(const Name::Enum&, const bool&) MOZ_DELETE; \

      inline int operator&(const int&, const Name::Enum&) MOZ_DELETE; \

      inline int operator&(const Name::Enum&, const int&) MOZ_DELETE; \

      inline int operator|(const int&, const Name::Enum&) MOZ_DELETE; \

      inline int operator|(const Name::Enum&, const int&) MOZ_DELETE; \

      inline int operator^(const int&, const Name::Enum&) MOZ_DELETE; \

      inline int operator^(const Name::Enum&, const int&) MOZ_DELETE; \

      inline int operator<<(const int&, const Name::Enum&) MOZ_DELETE; \

      inline int operator<<(const Name::Enum&, const int&) MOZ_DELETE; \

      inline int operator>>(const int&, const Name::Enum&) MOZ_DELETE; \

      inline int operator>>(const Name::Enum&, const int&) MOZ_DELETE; \

      inline int& operator+=(int&, const Name::Enum&) MOZ_DELETE; \

      inline int& operator-=(int&, const Name::Enum&) MOZ_DELETE; \

      inline int& operator*=(int&, const Name::Enum&) MOZ_DELETE; \

      inline int& operator/=(int&, const Name::Enum&) MOZ_DELETE; \

      inline int& operator%=(int&, const Name::Enum&) MOZ_DELETE; \

      inline int& operator&=(int&, const Name::Enum&) MOZ_DELETE; \

      inline int& operator|=(int&, const Name::Enum&) MOZ_DELETE; \

      inline int& operator^=(int&, const Name::Enum&) MOZ_DELETE; \

      inline int& operator<<=(int&, const Name::Enum&) MOZ_DELETE; \

      inline int& operator>>=(int&, const Name::Enum&) MOZ_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<typename T, MOZ_TEMPLATE_ENUM_CLASS_ENUM_TYPE(T) Value>

    *    struct S {};

    *

    *    MOZ_BEGIN_ENUM_CLASS(E)

    *      Foo,

    *      Bar

    *    MOZ_END_ENUM_CLASS(E)

    *

    *    S<E, E::Bar> 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 */