xpcom/base/AutoRestore.h

   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
  14 namespace mozilla {
  15
  16 /**
  17  * Save the current value of a variable and restore it when the object
  18  * goes out of scope.  For example:
  19  *   {
  20  *     AutoRestore<bool> savePainting(mIsPainting);
  21  *     mIsPainting = true;
  22  *
  23  *     // ... your code here ...
  24  *
  25  *     // mIsPainting is reset to its old value at the end of this block
  26  *   }
  27  */
  28 template <class T>
  29 class MOZ_RAII AutoRestore {
  30  private:
  31   T& mLocation;
  32   T mValue;
  33
  34  public:
  35   explicit AutoRestore(T& aValue) : mLocation(aValue), mValue(aValue) {}
  36   ~AutoRestore() { mLocation = mValue; }
  37   T SavedValue() const { return mValue; }
  38 };
  39
  40 }  // namespace mozilla
  41
  42 #endif /* !defined(mozilla_AutoRestore_h_) */