base/auto_reset.h

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