base/auto_reset.h

   1 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_AUTO_RESET_H_
   6 #define BASE_AUTO_RESET_H_
   7 #pragma once
   8
   9 #include "base/basictypes.h"
  10
  11 // AutoResetValue is useful for setting a variable to some value only
  12 // during a particular scope.  If you have code that has to add "var =
  13 // false;" or "var = old_var;" at all the exit points of a block, for
  14 // example, you would benefit from using this instead.
  15 //
  16 // This should be obvious, but note that the AutoResetValue instance
  17 // should have a shorter lifetime than the scoped_variable, to prevent
  18 // writing to invalid memory when the AutoResetValue goes out of
  19 // scope.
  20
  21 template<typename T>
  22 class AutoReset {
  23  public:
  24   AutoReset(T* scoped_variable, T new_value)
  25       : scoped_variable_(scoped_variable),
  26         original_value_(*scoped_variable) {
  27     *scoped_variable_ = new_value;
  28   }
  29
  30   ~AutoReset() { *scoped_variable_ = original_value_; }
  31
  32  private:
  33   T* scoped_variable_;
  34   T original_value_;
  35
  36   DISALLOW_COPY_AND_ASSIGN(AutoReset);
  37 };
  38
  39 #endif  // BASE_AUTO_RESET_H_