mark@chromium.org | 4688c26 | 2011-06-28 11:20:02 +0900 | [diff] [blame] | 1 | // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
pkasting@chromium.org | aea8162 | 2009-11-21 08:16:26 +0900 | [diff] [blame] | 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 | |
avi | a6a6a68 | 2015-12-27 07:15:14 +0900 | [diff] [blame] | 8 | #include "base/macros.h" |
pkasting@chromium.org | aea8162 | 2009-11-21 08:16:26 +0900 | [diff] [blame] | 9 | |
dbeam@chromium.org | 95d8c7d | 2012-11-21 13:44:14 +0900 | [diff] [blame] | 10 | // 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.org | aea8162 | 2009-11-21 08:16:26 +0900 | [diff] [blame] | 14 | // |
dbeam@chromium.org | 95d8c7d | 2012-11-21 13:44:14 +0900 | [diff] [blame] | 15 | // 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 | |
| 19 | namespace base { |
pkasting@chromium.org | aea8162 | 2009-11-21 08:16:26 +0900 | [diff] [blame] | 20 | |
gspencer@chromium.org | eb492ac | 2010-06-02 04:28:34 +0900 | [diff] [blame] | 21 | template<typename T> |
pkasting@chromium.org | aea8162 | 2009-11-21 08:16:26 +0900 | [diff] [blame] | 22 | class AutoReset { |
| 23 | public: |
gspencer@chromium.org | eb492ac | 2010-06-02 04:28:34 +0900 | [diff] [blame] | 24 | AutoReset(T* scoped_variable, T new_value) |
pkasting@chromium.org | aea8162 | 2009-11-21 08:16:26 +0900 | [diff] [blame] | 25 | : scoped_variable_(scoped_variable), |
| 26 | original_value_(*scoped_variable) { |
| 27 | *scoped_variable_ = new_value; |
| 28 | } |
gspencer@chromium.org | eb492ac | 2010-06-02 04:28:34 +0900 | [diff] [blame] | 29 | |
pkasting@chromium.org | aea8162 | 2009-11-21 08:16:26 +0900 | [diff] [blame] | 30 | ~AutoReset() { *scoped_variable_ = original_value_; } |
| 31 | |
| 32 | private: |
gspencer@chromium.org | eb492ac | 2010-06-02 04:28:34 +0900 | [diff] [blame] | 33 | T* scoped_variable_; |
| 34 | T original_value_; |
pkasting@chromium.org | aea8162 | 2009-11-21 08:16:26 +0900 | [diff] [blame] | 35 | |
| 36 | DISALLOW_COPY_AND_ASSIGN(AutoReset); |
| 37 | }; |
| 38 | |
danakj | 651c3e2 | 2015-03-07 10:51:42 +0900 | [diff] [blame] | 39 | } // namespace base |
dbeam@chromium.org | 95d8c7d | 2012-11-21 13:44:14 +0900 | [diff] [blame] | 40 | |
pkasting@chromium.org | aea8162 | 2009-11-21 08:16:26 +0900 | [diff] [blame] | 41 | #endif // BASE_AUTO_RESET_H_ |