Line data    Source code

       1              : /*
       2              :  *
       3              :  *    Copyright (c) 2020 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              : #pragma once
      19              : 
      20              : #include <type_traits>
      21              : 
      22              : namespace chip {
      23              : 
      24              : /**
      25              :  * A template function that casts a pointer of type From* to a pointer of type To*
      26              :  * and verifies that both From and To are trivially copyable structures, size of
      27              :  * To is not greater than size of From, and To doesn't have more strict alignment
      28              :  * requirements than From. That is to make sure that access to fields of To is safe.
      29              :  */
      30              : template <class ToPtr, class From>
      31        57304 : std::enable_if_t<std::is_pointer<ToPtr>::value, ToPtr> SafePointerCast(From * from)
      32              : {
      33              :     using To = std::remove_pointer_t<ToPtr>;
      34              :     static_assert(std::is_trivially_copyable<From>(), "Casting from a non-trivially copyable type");
      35              :     static_assert(std::is_trivially_copyable<To>(), "Casting to a non-trivially copyable type");
      36              :     static_assert(sizeof(From) >= sizeof(To), "Casting to a bigger type");
      37              :     static_assert(alignof(From) >= alignof(To), "Casting to a type with more strict alignment requirements");
      38        57304 :     return reinterpret_cast<ToPtr>(from);
      39              : }
      40              : 
      41              : } // namespace chip