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mark@chromium.org4688c262011-06-28 11:20:02 +09001// Copyright (c) 2011 The Chromium Authors. All rights reserved.
pkasting@chromium.orgaea81622009-11-21 08:16:26 +09002// 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
8#include "base/basictypes.h"
9
dbeam@chromium.org95d8c7d2012-11-21 13:44:14 +090010// base::AutoReset<> is useful for setting a variable to a new value only within
11// a particular scope. An base::AutoReset<> object resets a variable to its
12// original value upon destruction, making it an alternative to writing
13// "var = false;" or "var = old_val;" at all of a block's exit points.
pkasting@chromium.orgaea81622009-11-21 08:16:26 +090014//
dbeam@chromium.org95d8c7d2012-11-21 13:44:14 +090015// This should be obvious, but note that an base::AutoReset<> instance should
16// have a shorter lifetime than its scoped_variable, to prevent invalid memory
17// writes when the base::AutoReset<> object is destroyed.
18
19namespace base {
pkasting@chromium.orgaea81622009-11-21 08:16:26 +090020
gspencer@chromium.orgeb492ac2010-06-02 04:28:34 +090021template<typename T>
pkasting@chromium.orgaea81622009-11-21 08:16:26 +090022class AutoReset {
23 public:
gspencer@chromium.orgeb492ac2010-06-02 04:28:34 +090024 AutoReset(T* scoped_variable, T new_value)
pkasting@chromium.orgaea81622009-11-21 08:16:26 +090025 : scoped_variable_(scoped_variable),
26 original_value_(*scoped_variable) {
27 *scoped_variable_ = new_value;
28 }
gspencer@chromium.orgeb492ac2010-06-02 04:28:34 +090029
pkasting@chromium.orgaea81622009-11-21 08:16:26 +090030 ~AutoReset() { *scoped_variable_ = original_value_; }
31
32 private:
gspencer@chromium.orgeb492ac2010-06-02 04:28:34 +090033 T* scoped_variable_;
34 T original_value_;
pkasting@chromium.orgaea81622009-11-21 08:16:26 +090035
36 DISALLOW_COPY_AND_ASSIGN(AutoReset);
37};
38
dbeam@chromium.org95d8c7d2012-11-21 13:44:14 +090039}
40
pkasting@chromium.orgaea81622009-11-21 08:16:26 +090041#endif // BASE_AUTO_RESET_H_