1 /* 2 * Copyright (C) 2016 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef STAGEFRIGHT_FOUNDATION_TYPE_TRAITS_H_ 18 #define STAGEFRIGHT_FOUNDATION_TYPE_TRAITS_H_ 19 20 #include <type_traits> 21 22 #undef HIDE 23 #define HIDE __attribute__((visibility("hidden"))) 24 25 namespace android { 26 27 /** 28 * std::is_signed, is_unsigned and is_integral does not consider enums even though the standard 29 * considers them integral. Create modified versions of these here. Also create a wrapper around 30 * std::underlying_type that does not require checking if the type is an enum. 31 */ 32 33 /** 34 * Type support utility class to check if a type is an integral type or an enum. 35 */ 36 template<typename T> 37 struct HIDE is_integral_or_enum 38 : std::integral_constant<bool, std::is_integral<T>::value || std::is_enum<T>::value> { }; 39 40 /** 41 * Type support utility class to get the underlying std::is_integral supported type for a type. 42 * This returns the underlying type for enums, and the same type for types covered by 43 * std::is_integral. 44 * 45 * This is also used as a conditional to return an alternate type if the template param is not 46 * an integral or enum type (as in underlying_integral_type<T, TypeIfNotEnumOrIntegral>::type). 47 */ 48 template<typename T, 49 typename U=typename std::enable_if<is_integral_or_enum<T>::value>::type, 50 bool=std::is_enum<T>::value, 51 bool=std::is_integral<T>::value> 52 struct HIDE underlying_integral_type { 53 static_assert(!std::is_enum<T>::value, "T should not be enum here"); 54 static_assert(!std::is_integral<T>::value, "T should not be integral here"); 55 typedef U type; 56 }; 57 58 /** Specialization for enums. */ 59 template<typename T, typename U> 60 struct HIDE underlying_integral_type<T, U, true, false> { 61 static_assert(std::is_enum<T>::value, "T should be enum here"); 62 static_assert(!std::is_integral<T>::value, "T should not be integral here"); 63 typedef typename std::underlying_type<T>::type type; 64 }; 65 66 /** Specialization for non-enum std-integral types. */ 67 template<typename T, typename U> 68 struct HIDE underlying_integral_type<T, U, false, true> { 69 static_assert(!std::is_enum<T>::value, "T should not be enum here"); 70 static_assert(std::is_integral<T>::value, "T should be integral here"); 71 typedef T type; 72 }; 73 74 /** 75 * Type support utility class to check if the underlying integral type is signed. 76 */ 77 template<typename T> 78 struct HIDE is_signed_integral 79 : std::integral_constant<bool, std::is_signed< 80 typename underlying_integral_type<T, unsigned>::type>::value> { }; 81 82 /** 83 * Type support utility class to check if the underlying integral type is unsigned. 84 */ 85 template<typename T> 86 struct HIDE is_unsigned_integral 87 : std::integral_constant<bool, std::is_unsigned< 88 typename underlying_integral_type<T, signed>::type>::value> { 89 }; 90 91 /** 92 * Type support relationship query template. 93 * 94 * If T occurs as one of the types in Us with the same const-volatile qualifications, provides the 95 * member constant |value| equal to true. Otherwise value is false. 96 */ 97 template<typename T, typename ...Us> 98 struct HIDE is_one_of; 99 100 /// \if 0 101 /** 102 * Template specialization when first type matches the searched type. 103 */ 104 template<typename T, typename ...Us> 105 struct HIDE is_one_of<T, T, Us...> : std::true_type {}; 106 107 /** 108 * Template specialization when first type does not match the searched type. 109 */ 110 template<typename T, typename U, typename ...Us> 111 struct HIDE is_one_of<T, U, Us...> : is_one_of<T, Us...> {}; 112 113 /** 114 * Template specialization when there are no types to search. 115 */ 116 template<typename T> 117 struct HIDE is_one_of<T> : std::false_type {}; 118 /// \endif 119 120 /** 121 * Type support relationship query template. 122 * 123 * If all types in Us are unique, provides the member constant |value| equal to true. 124 * Otherwise value is false. 125 */ 126 template<typename ...Us> 127 struct HIDE are_unique; 128 129 /// \if 0 130 /** 131 * Template specialization when there are no types. 132 */ 133 template<> 134 struct HIDE are_unique<> : std::true_type {}; 135 136 /** 137 * Template specialization when there is at least one type to check. 138 */ 139 template<typename T, typename ...Us> 140 struct HIDE are_unique<T, Us...> 141 : std::integral_constant<bool, are_unique<Us...>::value && !is_one_of<T, Us...>::value> {}; 142 /// \endif 143 144 /// \if 0 145 template<size_t Base, typename T, typename ...Us> 146 struct HIDE _find_first_impl; 147 148 /** 149 * Template specialization when there are no types to search. 150 */ 151 template<size_t Base, typename T> 152 struct HIDE _find_first_impl<Base, T> : std::integral_constant<size_t, 0> {}; 153 154 /** 155 * Template specialization when T is the first type in Us. 156 */ 157 template<size_t Base, typename T, typename ...Us> 158 struct HIDE _find_first_impl<Base, T, T, Us...> : std::integral_constant<size_t, Base> {}; 159 160 /** 161 * Template specialization when T is not the first type in Us. 162 */ 163 template<size_t Base, typename T, typename U, typename ...Us> 164 struct HIDE _find_first_impl<Base, T, U, Us...> 165 : std::integral_constant<size_t, _find_first_impl<Base + 1, T, Us...>::value> {}; 166 167 /// \endif 168 169 /** 170 * Type support relationship query template. 171 * 172 * If T occurs in Us, index is the 1-based left-most index of T in Us. Otherwise, index is 0. 173 */ 174 template<typename T, typename ...Us> 175 struct HIDE find_first { 176 static constexpr size_t index = _find_first_impl<1, T, Us...>::value; 177 }; 178 179 /// \if 0 180 /** 181 * Helper class for find_first_convertible_to template. 182 * 183 * Adds a base index. 184 */ 185 template<size_t Base, typename T, typename ...Us> 186 struct HIDE _find_first_convertible_to_helper; 187 188 /** 189 * Template specialization for when there are more types to consider 190 */ 191 template<size_t Base, typename T, typename U, typename ...Us> 192 struct HIDE _find_first_convertible_to_helper<Base, T, U, Us...> { 193 static constexpr size_t index = 194 std::is_convertible<T, U>::value ? Base : 195 _find_first_convertible_to_helper<Base + 1, T, Us...>::index; 196 typedef typename std::conditional< 197 std::is_convertible<T, U>::value, U, 198 typename _find_first_convertible_to_helper<Base + 1, T, Us...>::type>::type type; 199 }; 200 201 /** 202 * Template specialization for when there are no more types to consider 203 */ 204 template<size_t Base, typename T> 205 struct HIDE _find_first_convertible_to_helper<Base, T> { 206 static constexpr size_t index = 0; 207 typedef void type; 208 }; 209 210 /// \endif 211 212 /** 213 * Type support template that returns the type that T can be implicitly converted into, and its 214 * index, from a list of other types (Us). 215 * 216 * Returns index of 0 and type of void if there are no convertible types. 217 * 218 * \param T type that is converted 219 * \param Us types into which the conversion is considered 220 */ 221 template<typename T, typename ...Us> 222 struct HIDE find_first_convertible_to : public _find_first_convertible_to_helper<1, T, Us...> { }; 223 224 } // namespace android 225 226 #endif // STAGEFRIGHT_FOUNDATION_TYPE_TRAITS_H_ 227 228
