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       1             : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2             : /* vim: set ts=8 sts=2 et sw=2 tw=80: */
       3             : /* This Source Code Form is subject to the terms of the Mozilla Public
       4             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       5             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       6             : 
       7             : /* functions for restoring saved values at the end of a C++ scope */
       8             : 
       9             : #ifndef mozilla_AutoRestore_h_
      10             : #define mozilla_AutoRestore_h_
      11             : 
      12             : #include "mozilla/Attributes.h" // MOZ_STACK_CLASS
      13             : #include "mozilla/GuardObjects.h"
      14             : 
      15             : namespace mozilla {
      16             : 
      17             : /**
      18             :  * Save the current value of a variable and restore it when the object
      19             :  * goes out of scope.  For example:
      20             :  *   {
      21             :  *     AutoRestore<bool> savePainting(mIsPainting);
      22             :  *     mIsPainting = true;
      23             :  *
      24             :  *     // ... your code here ...
      25             :  *
      26             :  *     // mIsPainting is reset to its old value at the end of this block
      27             :  *   }
      28             :  */
      29             : template<class T>
      30             : class MOZ_RAII AutoRestore
      31             : {
      32             : private:
      33             :   T& mLocation;
      34             :   T mValue;
      35             :   MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
      36             : public:
      37       13631 :   explicit AutoRestore(T& aValue MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
      38             :     : mLocation(aValue)
      39       13631 :     , mValue(aValue)
      40             :   {
      41       13631 :     MOZ_GUARD_OBJECT_NOTIFIER_INIT;
      42       13631 :   }
      43       13631 :   ~AutoRestore()
      44             :   {
      45       13631 :     mLocation = mValue;
      46       13631 :   }
      47          27 :   T SavedValue() const
      48             :   {
      49          27 :     return mValue;
      50             :   }
      51             : };
      52             : 
      53             : } // namespace mozilla
      54             : 
      55             : #endif /* !defined(mozilla_AutoRestore_h_) */