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
25namespace 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 */
36template<typename T>
37struct 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 */
48template<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>
52struct 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. */
59template<typename T, typename U>
60struct 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. */
67template<typename T, typename U>
68struct 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 */
77template<typename T>
78struct 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 */
85template<typename T>
86struct 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 */
97template<typename T, typename ...Us>
98struct HIDE is_one_of;
99
100/// \if 0
101/**
102 * Template specialization when first type matches the searched type.
103 */
104template<typename T, typename ...Us>
105struct 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 */
110template<typename T, typename U, typename ...Us>
111struct 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 */
116template<typename T>
117struct 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 */
126template<typename ...Us>
127struct HIDE are_unique;
128
129/// \if 0
130/**
131 * Template specialization when there are no types.
132 */
133template<>
134struct HIDE are_unique<> : std::true_type {};
135
136/**
137 * Template specialization when there is at least one type to check.
138 */
139template<typename T, typename ...Us>
140struct 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
145template<size_t Base, typename T, typename ...Us>
146struct HIDE _find_first_impl;
147
148/**
149 * Template specialization when there are no types to search.
150 */
151template<size_t Base, typename T>
152struct 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 */
157template<size_t Base, typename T, typename ...Us>
158struct 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 */
163template<size_t Base, typename T, typename U, typename ...Us>
164struct 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 */
174template<typename T, typename ...Us>
175struct 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 */
185template<size_t Base, typename T, typename ...Us>
186struct HIDE _find_first_convertible_to_helper;
187
188/**
189 * Template specialization for when there are more types to consider
190 */
191template<size_t Base, typename T, typename U, typename ...Us>
192struct 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 */
204template<size_t Base, typename T>
205struct 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 */
221template<typename T, typename ...Us>
222struct 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