/src/LPM/external.protobuf/include/absl/utility/utility.h
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1 | | // Copyright 2017 The Abseil Authors. |
2 | | // |
3 | | // Licensed under the Apache License, Version 2.0 (the "License"); |
4 | | // you may not use this file except in compliance with the License. |
5 | | // You may obtain a copy of the License at |
6 | | // |
7 | | // https://www.apache.org/licenses/LICENSE-2.0 |
8 | | // |
9 | | // Unless required by applicable law or agreed to in writing, software |
10 | | // distributed under the License is distributed on an "AS IS" BASIS, |
11 | | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
12 | | // See the License for the specific language governing permissions and |
13 | | // limitations under the License. |
14 | | // |
15 | | // This header file contains C++11 versions of standard <utility> header |
16 | | // abstractions available within C++14 and C++17, and are designed to be drop-in |
17 | | // replacement for code compliant with C++14 and C++17. |
18 | | // |
19 | | // The following abstractions are defined: |
20 | | // |
21 | | // * integer_sequence<T, Ints...> == std::integer_sequence<T, Ints...> |
22 | | // * index_sequence<Ints...> == std::index_sequence<Ints...> |
23 | | // * make_integer_sequence<T, N> == std::make_integer_sequence<T, N> |
24 | | // * make_index_sequence<N> == std::make_index_sequence<N> |
25 | | // * index_sequence_for<Ts...> == std::index_sequence_for<Ts...> |
26 | | // * apply<Functor, Tuple> == std::apply<Functor, Tuple> |
27 | | // * exchange<T> == std::exchange<T> |
28 | | // * make_from_tuple<T> == std::make_from_tuple<T> |
29 | | // |
30 | | // This header file also provides the tag types `in_place_t`, `in_place_type_t`, |
31 | | // and `in_place_index_t`, as well as the constant `in_place`, and |
32 | | // `constexpr` `std::move()` and `std::forward()` implementations in C++11. |
33 | | // |
34 | | // References: |
35 | | // |
36 | | // https://en.cppreference.com/w/cpp/utility/integer_sequence |
37 | | // https://en.cppreference.com/w/cpp/utility/apply |
38 | | // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3658.html |
39 | | |
40 | | #ifndef ABSL_UTILITY_UTILITY_H_ |
41 | | #define ABSL_UTILITY_UTILITY_H_ |
42 | | |
43 | | #include <cstddef> |
44 | | #include <cstdlib> |
45 | | #include <tuple> |
46 | | #include <utility> |
47 | | |
48 | | #include "absl/base/config.h" |
49 | | #include "absl/base/internal/inline_variable.h" |
50 | | #include "absl/base/internal/invoke.h" |
51 | | #include "absl/meta/type_traits.h" |
52 | | |
53 | | namespace absl { |
54 | | ABSL_NAMESPACE_BEGIN |
55 | | |
56 | | // integer_sequence |
57 | | // |
58 | | // Class template representing a compile-time integer sequence. An instantiation |
59 | | // of `integer_sequence<T, Ints...>` has a sequence of integers encoded in its |
60 | | // type through its template arguments (which is a common need when |
61 | | // working with C++11 variadic templates). `absl::integer_sequence` is designed |
62 | | // to be a drop-in replacement for C++14's `std::integer_sequence`. |
63 | | // |
64 | | // Example: |
65 | | // |
66 | | // template< class T, T... Ints > |
67 | | // void user_function(integer_sequence<T, Ints...>); |
68 | | // |
69 | | // int main() |
70 | | // { |
71 | | // // user_function's `T` will be deduced to `int` and `Ints...` |
72 | | // // will be deduced to `0, 1, 2, 3, 4`. |
73 | | // user_function(make_integer_sequence<int, 5>()); |
74 | | // } |
75 | | template <typename T, T... Ints> |
76 | | struct integer_sequence { |
77 | | using value_type = T; |
78 | | static constexpr size_t size() noexcept { return sizeof...(Ints); } |
79 | | }; |
80 | | |
81 | | // index_sequence |
82 | | // |
83 | | // A helper template for an `integer_sequence` of `size_t`, |
84 | | // `absl::index_sequence` is designed to be a drop-in replacement for C++14's |
85 | | // `std::index_sequence`. |
86 | | template <size_t... Ints> |
87 | | using index_sequence = integer_sequence<size_t, Ints...>; |
88 | | |
89 | | namespace utility_internal { |
90 | | |
91 | | template <typename Seq, size_t SeqSize, size_t Rem> |
92 | | struct Extend; |
93 | | |
94 | | // Note that SeqSize == sizeof...(Ints). It's passed explicitly for efficiency. |
95 | | template <typename T, T... Ints, size_t SeqSize> |
96 | | struct Extend<integer_sequence<T, Ints...>, SeqSize, 0> { |
97 | | using type = integer_sequence<T, Ints..., (Ints + SeqSize)...>; |
98 | | }; |
99 | | |
100 | | template <typename T, T... Ints, size_t SeqSize> |
101 | | struct Extend<integer_sequence<T, Ints...>, SeqSize, 1> { |
102 | | using type = integer_sequence<T, Ints..., (Ints + SeqSize)..., 2 * SeqSize>; |
103 | | }; |
104 | | |
105 | | // Recursion helper for 'make_integer_sequence<T, N>'. |
106 | | // 'Gen<T, N>::type' is an alias for 'integer_sequence<T, 0, 1, ... N-1>'. |
107 | | template <typename T, size_t N> |
108 | | struct Gen { |
109 | | using type = |
110 | | typename Extend<typename Gen<T, N / 2>::type, N / 2, N % 2>::type; |
111 | | }; |
112 | | |
113 | | template <typename T> |
114 | | struct Gen<T, 0> { |
115 | | using type = integer_sequence<T>; |
116 | | }; |
117 | | |
118 | | template <typename T> |
119 | | struct InPlaceTypeTag { |
120 | | explicit InPlaceTypeTag() = delete; |
121 | | InPlaceTypeTag(const InPlaceTypeTag&) = delete; |
122 | | InPlaceTypeTag& operator=(const InPlaceTypeTag&) = delete; |
123 | | }; |
124 | | |
125 | | template <size_t I> |
126 | | struct InPlaceIndexTag { |
127 | | explicit InPlaceIndexTag() = delete; |
128 | | InPlaceIndexTag(const InPlaceIndexTag&) = delete; |
129 | | InPlaceIndexTag& operator=(const InPlaceIndexTag&) = delete; |
130 | | }; |
131 | | |
132 | | } // namespace utility_internal |
133 | | |
134 | | // Compile-time sequences of integers |
135 | | |
136 | | // make_integer_sequence |
137 | | // |
138 | | // This template alias is equivalent to |
139 | | // `integer_sequence<int, 0, 1, ..., N-1>`, and is designed to be a drop-in |
140 | | // replacement for C++14's `std::make_integer_sequence`. |
141 | | template <typename T, T N> |
142 | | using make_integer_sequence = typename utility_internal::Gen<T, N>::type; |
143 | | |
144 | | // make_index_sequence |
145 | | // |
146 | | // This template alias is equivalent to `index_sequence<0, 1, ..., N-1>`, |
147 | | // and is designed to be a drop-in replacement for C++14's |
148 | | // `std::make_index_sequence`. |
149 | | template <size_t N> |
150 | | using make_index_sequence = make_integer_sequence<size_t, N>; |
151 | | |
152 | | // index_sequence_for |
153 | | // |
154 | | // Converts a typename pack into an index sequence of the same length, and |
155 | | // is designed to be a drop-in replacement for C++14's |
156 | | // `std::index_sequence_for()` |
157 | | template <typename... Ts> |
158 | | using index_sequence_for = make_index_sequence<sizeof...(Ts)>; |
159 | | |
160 | | // Tag types |
161 | | |
162 | | #ifdef ABSL_USES_STD_OPTIONAL |
163 | | |
164 | | using std::in_place_t; |
165 | | using std::in_place; |
166 | | |
167 | | #else // ABSL_USES_STD_OPTIONAL |
168 | | |
169 | | // in_place_t |
170 | | // |
171 | | // Tag type used to specify in-place construction, such as with |
172 | | // `absl::optional`, designed to be a drop-in replacement for C++17's |
173 | | // `std::in_place_t`. |
174 | | struct in_place_t {}; |
175 | | |
176 | | ABSL_INTERNAL_INLINE_CONSTEXPR(in_place_t, in_place, {}); |
177 | | |
178 | | #endif // ABSL_USES_STD_OPTIONAL |
179 | | |
180 | | #if defined(ABSL_USES_STD_ANY) || defined(ABSL_USES_STD_VARIANT) |
181 | | using std::in_place_type; |
182 | | using std::in_place_type_t; |
183 | | #else |
184 | | |
185 | | // in_place_type_t |
186 | | // |
187 | | // Tag type used for in-place construction when the type to construct needs to |
188 | | // be specified, such as with `absl::any`, designed to be a drop-in replacement |
189 | | // for C++17's `std::in_place_type_t`. |
190 | | template <typename T> |
191 | | using in_place_type_t = void (*)(utility_internal::InPlaceTypeTag<T>); |
192 | | |
193 | | template <typename T> |
194 | | void in_place_type(utility_internal::InPlaceTypeTag<T>) {} |
195 | | #endif // ABSL_USES_STD_ANY || ABSL_USES_STD_VARIANT |
196 | | |
197 | | #ifdef ABSL_USES_STD_VARIANT |
198 | | using std::in_place_index; |
199 | | using std::in_place_index_t; |
200 | | #else |
201 | | |
202 | | // in_place_index_t |
203 | | // |
204 | | // Tag type used for in-place construction when the type to construct needs to |
205 | | // be specified, such as with `absl::any`, designed to be a drop-in replacement |
206 | | // for C++17's `std::in_place_index_t`. |
207 | | template <size_t I> |
208 | | using in_place_index_t = void (*)(utility_internal::InPlaceIndexTag<I>); |
209 | | |
210 | | template <size_t I> |
211 | | void in_place_index(utility_internal::InPlaceIndexTag<I>) {} |
212 | | #endif // ABSL_USES_STD_VARIANT |
213 | | |
214 | | // Constexpr move and forward |
215 | | |
216 | | // move() |
217 | | // |
218 | | // A constexpr version of `std::move()`, designed to be a drop-in replacement |
219 | | // for C++14's `std::move()`. |
220 | | template <typename T> |
221 | | constexpr absl::remove_reference_t<T>&& move(T&& t) noexcept { |
222 | | return static_cast<absl::remove_reference_t<T>&&>(t); |
223 | | } |
224 | | |
225 | | // forward() |
226 | | // |
227 | | // A constexpr version of `std::forward()`, designed to be a drop-in replacement |
228 | | // for C++14's `std::forward()`. |
229 | | template <typename T> |
230 | | constexpr T&& forward( |
231 | 0 | absl::remove_reference_t<T>& t) noexcept { // NOLINT(runtime/references) |
232 | 0 | return static_cast<T&&>(t); |
233 | 0 | } Unexecuted instantiation: unsigned int&& absl::lts_20230125::forward<unsigned int>(std::__1::remove_reference<unsigned int>::type&) Unexecuted instantiation: absl::lts_20230125::string_view&& absl::lts_20230125::forward<absl::lts_20230125::string_view>(std::__1::remove_reference<absl::lts_20230125::string_view>::type&) Unexecuted instantiation: char const*&& absl::lts_20230125::forward<char const*>(std::__1::remove_reference<char const*>::type&) Unexecuted instantiation: absl::lts_20230125::container_internal::HashtablezInfoHandle&& absl::lts_20230125::forward<absl::lts_20230125::container_internal::HashtablezInfoHandle>(std::__1::remove_reference<absl::lts_20230125::container_internal::HashtablezInfoHandle>::type&) Unexecuted instantiation: unsigned long& absl::lts_20230125::forward<unsigned long&>(std::__1::remove_reference<unsigned long&>::type&) Unexecuted instantiation: void (*&&absl::lts_20230125::forward<void (*)(absl::lts_20230125::string_view)>(std::__1::remove_reference<void (*)(absl::lts_20230125::string_view)>::type&))(absl::lts_20230125::string_view) |
234 | | |
235 | | namespace utility_internal { |
236 | | // Helper method for expanding tuple into a called method. |
237 | | template <typename Functor, typename Tuple, std::size_t... Indexes> |
238 | | auto apply_helper(Functor&& functor, Tuple&& t, index_sequence<Indexes...>) |
239 | | -> decltype(absl::base_internal::invoke( |
240 | | absl::forward<Functor>(functor), |
241 | | std::get<Indexes>(absl::forward<Tuple>(t))...)) { |
242 | | return absl::base_internal::invoke( |
243 | | absl::forward<Functor>(functor), |
244 | | std::get<Indexes>(absl::forward<Tuple>(t))...); |
245 | | } |
246 | | |
247 | | } // namespace utility_internal |
248 | | |
249 | | // apply |
250 | | // |
251 | | // Invokes a Callable using elements of a tuple as its arguments. |
252 | | // Each element of the tuple corresponds to an argument of the call (in order). |
253 | | // Both the Callable argument and the tuple argument are perfect-forwarded. |
254 | | // For member-function Callables, the first tuple element acts as the `this` |
255 | | // pointer. `absl::apply` is designed to be a drop-in replacement for C++17's |
256 | | // `std::apply`. Unlike C++17's `std::apply`, this is not currently `constexpr`. |
257 | | // |
258 | | // Example: |
259 | | // |
260 | | // class Foo { |
261 | | // public: |
262 | | // void Bar(int); |
263 | | // }; |
264 | | // void user_function1(int, std::string); |
265 | | // void user_function2(std::unique_ptr<Foo>); |
266 | | // auto user_lambda = [](int, int) {}; |
267 | | // |
268 | | // int main() |
269 | | // { |
270 | | // std::tuple<int, std::string> tuple1(42, "bar"); |
271 | | // // Invokes the first user function on int, std::string. |
272 | | // absl::apply(&user_function1, tuple1); |
273 | | // |
274 | | // std::tuple<std::unique_ptr<Foo>> tuple2(absl::make_unique<Foo>()); |
275 | | // // Invokes the user function that takes ownership of the unique |
276 | | // // pointer. |
277 | | // absl::apply(&user_function2, std::move(tuple2)); |
278 | | // |
279 | | // auto foo = absl::make_unique<Foo>(); |
280 | | // std::tuple<Foo*, int> tuple3(foo.get(), 42); |
281 | | // // Invokes the method Bar on foo with one argument, 42. |
282 | | // absl::apply(&Foo::Bar, tuple3); |
283 | | // |
284 | | // std::tuple<int, int> tuple4(8, 9); |
285 | | // // Invokes a lambda. |
286 | | // absl::apply(user_lambda, tuple4); |
287 | | // } |
288 | | template <typename Functor, typename Tuple> |
289 | | auto apply(Functor&& functor, Tuple&& t) |
290 | | -> decltype(utility_internal::apply_helper( |
291 | | absl::forward<Functor>(functor), absl::forward<Tuple>(t), |
292 | | absl::make_index_sequence<std::tuple_size< |
293 | | typename std::remove_reference<Tuple>::type>::value>{})) { |
294 | | return utility_internal::apply_helper( |
295 | | absl::forward<Functor>(functor), absl::forward<Tuple>(t), |
296 | | absl::make_index_sequence<std::tuple_size< |
297 | | typename std::remove_reference<Tuple>::type>::value>{}); |
298 | | } |
299 | | |
300 | | // exchange |
301 | | // |
302 | | // Replaces the value of `obj` with `new_value` and returns the old value of |
303 | | // `obj`. `absl::exchange` is designed to be a drop-in replacement for C++14's |
304 | | // `std::exchange`. |
305 | | // |
306 | | // Example: |
307 | | // |
308 | | // Foo& operator=(Foo&& other) { |
309 | | // ptr1_ = absl::exchange(other.ptr1_, nullptr); |
310 | | // int1_ = absl::exchange(other.int1_, -1); |
311 | | // return *this; |
312 | | // } |
313 | | template <typename T, typename U = T> |
314 | | T exchange(T& obj, U&& new_value) { |
315 | | T old_value = absl::move(obj); |
316 | | obj = absl::forward<U>(new_value); |
317 | | return old_value; |
318 | | } |
319 | | |
320 | | namespace utility_internal { |
321 | | template <typename T, typename Tuple, size_t... I> |
322 | | T make_from_tuple_impl(Tuple&& tup, absl::index_sequence<I...>) { |
323 | | return T(std::get<I>(std::forward<Tuple>(tup))...); |
324 | | } |
325 | | } // namespace utility_internal |
326 | | |
327 | | // make_from_tuple |
328 | | // |
329 | | // Given the template parameter type `T` and a tuple of arguments |
330 | | // `std::tuple(arg0, arg1, ..., argN)` constructs an object of type `T` as if by |
331 | | // calling `T(arg0, arg1, ..., argN)`. |
332 | | // |
333 | | // Example: |
334 | | // |
335 | | // std::tuple<const char*, size_t> args("hello world", 5); |
336 | | // auto s = absl::make_from_tuple<std::string>(args); |
337 | | // assert(s == "hello"); |
338 | | // |
339 | | template <typename T, typename Tuple> |
340 | | constexpr T make_from_tuple(Tuple&& tup) { |
341 | | return utility_internal::make_from_tuple_impl<T>( |
342 | | std::forward<Tuple>(tup), |
343 | | absl::make_index_sequence< |
344 | | std::tuple_size<absl::decay_t<Tuple>>::value>{}); |
345 | | } |
346 | | |
347 | | ABSL_NAMESPACE_END |
348 | | } // namespace absl |
349 | | |
350 | | #endif // ABSL_UTILITY_UTILITY_H_ |