gecko-dev/xpcom/glue/AutoRestore.h

/* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* functions for restoring saved values at the end of a C++ scope */

#ifndef mozilla_AutoRestore_h_
#define mozilla_AutoRestore_h_

#include "mozilla/Attributes.h" // MOZ_STACK_CLASS
#include "mozilla/GuardObjects.h"

namespace mozilla {

  /**
   * Save the current value of a variable and restore it when the object
   * goes out of scope.  For example:
   *   {
   *     AutoRestore<bool> savePainting(mIsPainting);
   *     mIsPainting = true;
   *     
   *     // ... your code here ...
   *
   *     // mIsPainting is reset to its old value at the end of this block
   *   }
   */
  template <class T>
  class MOZ_STACK_CLASS AutoRestore
  {
  private:
    T& mLocation;
    T mValue;
    MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
  public:
    AutoRestore(T& aValue MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
      : mLocation(aValue), mValue(aValue)
    {
      MOZ_GUARD_OBJECT_NOTIFIER_INIT;
    }
    ~AutoRestore() { mLocation = mValue; }
  };

} // namespace mozilla

#endif /* !defined(mozilla_AutoRestore_h_) */