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