| /* |
| * Copyright (C) 2016 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef STAGEFRIGHT_FOUNDATION_TYPE_TRAITS_H_ |
| #define STAGEFRIGHT_FOUNDATION_TYPE_TRAITS_H_ |
| |
| #include <type_traits> |
| |
| namespace android { |
| |
| /** |
| * std::is_signed, is_unsigned and is_integral does not consider enums even though the standard |
| * considers them integral. Create modified versions of these here. Also create a wrapper around |
| * std::underlying_type that does not require checking if the type is an enum. |
| */ |
| |
| /** |
| * Type support utility class to check if a type is an integral type or an enum. |
| */ |
| template<typename T> |
| struct is_integral_or_enum |
| : std::integral_constant<bool, std::is_integral<T>::value || std::is_enum<T>::value> { }; |
| |
| /** |
| * Type support utility class to get the underlying std::is_integral supported type for a type. |
| * This returns the underlying type for enums, and the same type for types covered by |
| * std::is_integral. |
| * |
| * This is also used as a conditional to return an alternate type if the template param is not |
| * an integral or enum type (as in underlying_integral_type<T, TypeIfNotEnumOrIntegral>::type). |
| */ |
| template<typename T, |
| typename U=typename std::enable_if<is_integral_or_enum<T>::value>::type, |
| bool=std::is_enum<T>::value, |
| bool=std::is_integral<T>::value> |
| struct underlying_integral_type { |
| static_assert(!std::is_enum<T>::value, "T should not be enum here"); |
| static_assert(!std::is_integral<T>::value, "T should not be integral here"); |
| typedef U type; |
| }; |
| |
| /** Specialization for enums. */ |
| template<typename T, typename U> |
| struct underlying_integral_type<T, U, true, false> { |
| static_assert(std::is_enum<T>::value, "T should be enum here"); |
| static_assert(!std::is_integral<T>::value, "T should not be integral here"); |
| typedef typename std::underlying_type<T>::type type; |
| }; |
| |
| /** Specialization for non-enum std-integral types. */ |
| template<typename T, typename U> |
| struct underlying_integral_type<T, U, false, true> { |
| static_assert(!std::is_enum<T>::value, "T should not be enum here"); |
| static_assert(std::is_integral<T>::value, "T should be integral here"); |
| typedef T type; |
| }; |
| |
| /** |
| * Type support utility class to check if the underlying integral type is signed. |
| */ |
| template<typename T> |
| struct is_signed_integral |
| : std::integral_constant<bool, std::is_signed< |
| typename underlying_integral_type<T, unsigned>::type>::value> { }; |
| |
| /** |
| * Type support utility class to check if the underlying integral type is unsigned. |
| */ |
| template<typename T> |
| struct is_unsigned_integral |
| : std::integral_constant<bool, std::is_unsigned< |
| typename underlying_integral_type<T, signed>::type>::value> { |
| }; |
| |
| /** |
| * Type support relationship query template. |
| * |
| * If T occurs as one of the types in Us with the same const-volatile qualifications, provides the |
| * member constant |value| equal to true. Otherwise value is false. |
| */ |
| template<typename T, typename ...Us> |
| struct is_one_of; |
| |
| /// \if 0 |
| /** |
| * Template specialization when first type matches the searched type. |
| */ |
| template<typename T, typename ...Us> |
| struct is_one_of<T, T, Us...> : std::true_type {}; |
| |
| /** |
| * Template specialization when first type does not match the searched type. |
| */ |
| template<typename T, typename U, typename ...Us> |
| struct is_one_of<T, U, Us...> : is_one_of<T, Us...> {}; |
| |
| /** |
| * Template specialization when there are no types to search. |
| */ |
| template<typename T> |
| struct is_one_of<T> : std::false_type {}; |
| /// \endif |
| |
| /** |
| * Type support relationship query template. |
| * |
| * If all types in Us are unique, provides the member constant |value| equal to true. |
| * Otherwise value is false. |
| */ |
| template<typename ...Us> |
| struct are_unique; |
| |
| /// \if 0 |
| /** |
| * Template specialization when there are no types. |
| */ |
| template<> |
| struct are_unique<> : std::true_type {}; |
| |
| /** |
| * Template specialization when there is at least one type to check. |
| */ |
| template<typename T, typename ...Us> |
| struct are_unique<T, Us...> |
| : std::integral_constant<bool, are_unique<Us...>::value && !is_one_of<T, Us...>::value> {}; |
| /// \endif |
| |
| /// \if 0 |
| template<size_t Base, typename T, typename ...Us> |
| struct _find_first_impl; |
| |
| /** |
| * Template specialization when there are no types to search. |
| */ |
| template<size_t Base, typename T> |
| struct _find_first_impl<Base, T> : std::integral_constant<size_t, 0> {}; |
| |
| /** |
| * Template specialization when T is the first type in Us. |
| */ |
| template<size_t Base, typename T, typename ...Us> |
| struct _find_first_impl<Base, T, T, Us...> : std::integral_constant<size_t, Base> {}; |
| |
| /** |
| * Template specialization when T is not the first type in Us. |
| */ |
| template<size_t Base, typename T, typename U, typename ...Us> |
| struct _find_first_impl<Base, T, U, Us...> |
| : std::integral_constant<size_t, _find_first_impl<Base + 1, T, Us...>::value> {}; |
| |
| /// \endif |
| |
| /** |
| * Type support relationship query template. |
| * |
| * If T occurs in Us, index is the 1-based left-most index of T in Us. Otherwise, index is 0. |
| */ |
| template<typename T, typename ...Us> |
| struct find_first { |
| static constexpr size_t index = _find_first_impl<1, T, Us...>::value; |
| }; |
| |
| /// \if 0 |
| /** |
| * Helper class for find_first_convertible_to template. |
| * |
| * Adds a base index. |
| */ |
| template<size_t Base, typename T, typename ...Us> |
| struct _find_first_convertible_to_helper; |
| |
| /** |
| * Template specialization for when there are more types to consider |
| */ |
| template<size_t Base, typename T, typename U, typename ...Us> |
| struct _find_first_convertible_to_helper<Base, T, U, Us...> { |
| static constexpr size_t index = |
| std::is_convertible<T, U>::value ? Base : |
| _find_first_convertible_to_helper<Base + 1, T, Us...>::index; |
| typedef typename std::conditional< |
| std::is_convertible<T, U>::value, U, |
| typename _find_first_convertible_to_helper<Base + 1, T, Us...>::type>::type type; |
| }; |
| |
| /** |
| * Template specialization for when there are no more types to consider |
| */ |
| template<size_t Base, typename T> |
| struct _find_first_convertible_to_helper<Base, T> { |
| static constexpr size_t index = 0; |
| typedef void type; |
| }; |
| |
| /// \endif |
| |
| /** |
| * Type support template that returns the type that T can be implicitly converted into, and its |
| * index, from a list of other types (Us). |
| * |
| * Returns index of 0 and type of void if there are no convertible types. |
| * |
| * \param T type that is converted |
| * \param Us types into which the conversion is considered |
| */ |
| template<typename T, typename ...Us> |
| struct find_first_convertible_to : public _find_first_convertible_to_helper<1, T, Us...> { }; |
| |
| } // namespace android |
| |
| #endif // STAGEFRIGHT_FOUNDATION_TYPE_TRAITS_H_ |
| |