cef/include/base/cef_auto_reset.h

91 lines
3.5 KiB
C++

// Copyright (c) 2014 Marshall A. Greenblatt. Portions copyright (c) 2011
// Google Inc. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the name Chromium Embedded
// Framework nor the names of its contributors may be used to endorse
// or promote products derived from this software without specific prior
// written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// 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.
#ifndef CEF_INCLUDE_BASE_CEF_AUTO_RESET_H_
#define CEF_INCLUDE_BASE_CEF_AUTO_RESET_H_
#pragma once
#if defined(USING_CHROMIUM_INCLUDES)
// When building CEF include the Chromium header directly.
#include "base/auto_reset.h"
#else // !USING_CHROMIUM_INCLUDES
// The following is substantially similar to the Chromium implementation.
// If the Chromium implementation diverges the below implementation should be
// updated to match.
#include <utility>
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 // !USING_CHROMIUM_INCLUDES
#endif // CEF_INCLUDE_BASE_CEF_AUTO_RESET_H_