1 // Copyright (c) 2011 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 8 #include <utility> 9 10 #include "base/macros.h" 11 12 // base::AutoReset<> is useful for setting a variable to a new value only within 13 // a particular scope. An base::AutoReset<> object resets a variable to its 14 // original value upon destruction, making it an alternative to writing 15 // "var = false;" or "var = old_val;" at all of a block's exit points. 16 // 17 // This should be obvious, but note that an base::AutoReset<> instance should 18 // have a shorter lifetime than its scoped_variable, to prevent invalid memory 19 // writes when the base::AutoReset<> object is destroyed. 20 21 namespace base { 22 23 template<typename T> 24 class AutoReset { 25 public: 26 AutoReset(T* scoped_variable, T new_value) 27 : scoped_variable_(scoped_variable), 28 original_value_(std::move(*scoped_variable)) { 29 *scoped_variable_ = std::move(new_value); 30 } 31 32 ~AutoReset() { *scoped_variable_ = std::move(original_value_); } 33 34 private: 35 T* scoped_variable_; 36 T original_value_; 37 38 DISALLOW_COPY_AND_ASSIGN(AutoReset); 39 }; 40 41 } // namespace base 42 43 #endif // BASE_AUTO_RESET_H_ 44
