53 lines
1.6 KiB
C
53 lines
1.6 KiB
C
|
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
|
||
|
|
// Use of this source code is governed by a BSD-style license that can be
|
||
|
|
// found in the LICENSE file.
|
||
|
|
|
||
|
|
#ifndef BASE_AUTO_RESET_H_
|
||
|
|
#define BASE_AUTO_RESET_H_
|
||
|
|
|
||
|
|
#include <utility>
|
||
|
|
|
||
|
|
// base::AutoReset<> is useful for setting a variable to a new value only within
|
||
|
|
// a particular scope. An base::AutoReset<> object resets a variable to its
|
||
|
|
// original value upon destruction, making it an alternative to writing
|
||
|
|
// "var = false;" or "var = old_val;" at all of a block's exit points.
|
||
|
|
//
|
||
|
|
// This should be obvious, but note that an base::AutoReset<> instance should
|
||
|
|
// have a shorter lifetime than its scoped_variable, to prevent invalid memory
|
||
|
|
// writes when the base::AutoReset<> object is destroyed.
|
||
|
|
|
||
|
|
namespace base {
|
||
|
|
|
||
|
|
template <typename T>
|
||
|
|
class AutoReset {
|
||
|
|
public:
|
||
|
|
template <typename U>
|
||
|
|
AutoReset(T* scoped_variable, U&& new_value)
|
||
|
|
: scoped_variable_(scoped_variable),
|
||
|
|
original_value_(
|
||
|
|
std::exchange(*scoped_variable_, std::forward<U>(new_value))) {}
|
||
|
|
|
||
|
|
AutoReset(AutoReset&& other)
|
||
|
|
: scoped_variable_(std::exchange(other.scoped_variable_, nullptr)),
|
||
|
|
original_value_(std::move(other.original_value_)) {}
|
||
|
|
|
||
|
|
AutoReset& operator=(AutoReset&& rhs) {
|
||
|
|
scoped_variable_ = std::exchange(rhs.scoped_variable_, nullptr);
|
||
|
|
original_value_ = std::move(rhs.original_value_);
|
||
|
|
return *this;
|
||
|
|
}
|
||
|
|
|
||
|
|
~AutoReset() {
|
||
|
|
if (scoped_variable_)
|
||
|
|
*scoped_variable_ = std::move(original_value_);
|
||
|
|
}
|
||
|
|
|
||
|
|
private:
|
||
|
|
T* scoped_variable_;
|
||
|
|
T original_value_;
|
||
|
|
};
|
||
|
|
|
||
|
|
} // namespace base
|
||
|
|
|
||
|
|
#endif // BASE_AUTO_RESET_H_
|