Line data    Source code

       1             : /*
       2             :  *
       3             :  *    Copyright (c) 2024 Project CHIP Authors
       4             :  *    All rights reserved.
       5             :  *
       6             :  *    Licensed under the Apache License, Version 2.0 (the "License");
       7             :  *    you may not use this file except in compliance with the License.
       8             :  *    You may obtain a copy of the License at
       9             :  *
      10             :  *        http://www.apache.org/licenses/LICENSE-2.0
      11             :  *
      12             :  *    Unless required by applicable law or agreed to in writing, software
      13             :  *    distributed under the License is distributed on an "AS IS" BASIS,
      14             :  *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      15             :  *    See the License for the specific language governing permissions and
      16             :  *    limitations under the License.
      17             :  */
      18             : #pragma once
      19             : 
      20             : namespace chip {
      21             : 
      22             : template <typename T>
      23             : class ScopedChange;
      24             : 
      25             : /// Allows a value to only be changed within a scope.
      26             : ///
      27             : /// Generally used to force determinism for unit test execution.
      28             : ///
      29             : /// When a variable of this type is used, it should
      30             : /// only be changed via `ScopedChange`.
      31             : template <typename T>
      32             : class ScopedChangeOnly
      33             : {
      34             : public:
      35          49 :     explicit ScopedChangeOnly(T initial) : mValue(initial) {}
      36           0 :     operator T() const { return mValue; }
      37             : 
      38             : private:
      39             :     T mValue;
      40             : 
      41             :     // Expected to be used only by ScopedChange<T> only
      42             :     T & InternalMutableValue() { return mValue; }
      43             :     friend class ScopedChange<T>;
      44             : };
      45             : 
      46             : /// Allows a scoped mutation to occur on a variable.
      47             : ///
      48             : /// When an instance of this class goes out of scope, the variable
      49             : /// will be reset to the default.
      50             : ///
      51             : /// Example usage
      52             : ///
      53             : /// int              a = 123;
      54             : /// ScopedChangeOnly b(234);
      55             : ///
      56             : /// /* a == 123, b == 234 */
      57             : /// {
      58             : ///    ScopedChange changeA(a, 321);
      59             : ///    /* a == 321, b == 234 */
      60             : ///    {
      61             : ///       ScopedChange changeB(b, 10);
      62             : ///       /* a == 321, b == 10 */
      63             : ///    }
      64             : ///    /* a == 321, b == 234 */
      65             : /// }
      66             : /// /* a == 123, b == 234 */
      67             : ///
      68             : template <typename T>
      69             : class ScopedChange
      70             : {
      71             : public:
      72             :     ScopedChange(ScopedChangeOnly<T> & what, T value) : mValue(what.InternalMutableValue()), mOriginal(what) { mValue = value; }
      73             :     ScopedChange(T & what, T value) : mValue(what), mOriginal(what) { mValue = value; }
      74             :     ~ScopedChange() { mValue = mOriginal; }
      75             : 
      76             : private:
      77             :     T & mValue;
      78             :     T mOriginal;
      79             : };
      80             : 
      81             : } // namespace chip