Line data    Source code

       1             : /*
       2             :  *
       3             :  *    Copyright (c) 2021 Project CHIP Authors
       4             :  *
       5             :  *    Licensed under the Apache License, Version 2.0 (the "License");
       6             :  *    you may not use this file except in compliance with the License.
       7             :  *    You may obtain a copy of the License at
       8             :  *
       9             :  *        http://www.apache.org/licenses/LICENSE-2.0
      10             :  *
      11             :  *    Unless required by applicable law or agreed to in writing, software
      12             :  *    distributed under the License is distributed on an "AS IS" BASIS,
      13             :  *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      14             :  *    See the License for the specific language governing permissions and
      15             :  *    limitations under the License.
      16             :  */
      17             : 
      18             : /**
      19             :  *    @file
      20             :  *      This file defines and implements a number of miscellaneous
      21             :  *      templates for simplify code with handling types.
      22             :  *
      23             :  */
      24             : 
      25             : #pragma once
      26             : 
      27             : #include <type_traits>
      28             : 
      29             : namespace chip {
      30             : 
      31             : /**
      32             :  * @brief Implemented std::to_underlying introduced in C++23.
      33             :  */
      34             : template <class T>
      35      844368 : constexpr std::underlying_type_t<T> to_underlying(T e)
      36             : {
      37             :     static_assert(std::is_enum<T>::value, "to_underlying called to non-enum values.");
      38      844368 :     return static_cast<std::underlying_type_t<T>>(e);
      39             : }
      40             : 
      41             : /**
      42             :  * @brief This template is not designed to be used directly. A common pattern to check the presence of a member of a class is:
      43             :  *
      44             :  * \cond
      45             :  * template <typename T>
      46             :  * class IsMagic
      47             :  * {
      48             :  * private:
      49             :  *     template <typename Tp>
      50             :  *     static auto TestHasMagic(int) -> TemplatedTrueType<decltype(&Tp::Magic)>;
      51             :  *
      52             :  *     template <typename Tp>
      53             :  *     static auto TestHasMagic(long) -> std::false_type;
      54             :  *
      55             :  * public:
      56             :  *     static constexpr bool value = decltype(TestHasMagic<std::decay_t<T>>(0))::value;
      57             :  * };
      58             :  * \endcond
      59             :  *
      60             :  *   The compiler will try to match TestHasMagicFunction(int) first, if MagicFunction is a member function of T, the match succeed
      61             :  * and HasMagicFunction is an alias of std::true_type. If MagicFunction is not a member function of T, the match of
      62             :  * TestHasMagicFunction(int) will result in compile error, due to SFINAE, compiler will try the next candicate, which is
      63             :  * TestHasMagicFunction(long), it will always success for all types, and HasMagicFunction becomes an alias of std::false_type.
      64             :  */
      65             : template <typename T>
      66             : using TemplatedTrueType = std::true_type;
      67             : 
      68             : } // namespace chip