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 "base/macros.h" 9 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. 14 // 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 { 20 21 template<typename T> 22 class AutoReset { 23 public: AutoReset(T * scoped_variable,T new_value)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 ~AutoReset()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 } // namespace base 40 41 #endif // BASE_AUTO_RESET_H_ 42