| // Copyright 2022 The ChromiumOS Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef FACED_UTIL_TEMPLATE_H_ |
| #define FACED_UTIL_TEMPLATE_H_ |
| |
| #include <tuple> |
| #include <utility> |
| |
| namespace faced { |
| |
| // Given a parameter pack, return: |
| // |
| // * An error if the pack is empty; |
| // * Type T if the pack is a single type T |
| // * Type std::tuple<T...> if the pack is two or more types. |
| // |
| // For example: |
| // |
| // TupleOrSingleton<int>::type == int |
| // TupleOrSingleton<int, float>::type == std::tuple<int, float> |
| // TupleOrSingleton<>::type == <compile-time error> |
| // |
| template <typename... Args> |
| using TupleOrSingleton = typename std::conditional< |
| (sizeof...(Args) == 1), |
| typename std::tuple_element<0, std::tuple<Args...>>::type, |
| typename std::tuple<Args...>>; |
| |
| } // namespace faced |
| |
| #endif // FACED_UTIL_TEMPLATE_H_ |
