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