auto_reset.h revision 3345a6884c488ff3a535c2c9acdd33d74b37e311 
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
21template<typename T>
22class 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_
40