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/*
* Copyright (C) 2011 Google Inc. All rights reserved.
* Copyright (C) 2016 Apple 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:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS 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 APPLE OR ITS 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.
*/
#pragma once
#include <wtf/Noncopyable.h>
#include <wtf/StdLibExtras.h>
namespace WTF {
// SetForScope<> is useful for setting a variable to a new value only within a
// particular scope. An SetForScope<> object changes a variable to its original
// value upon destruction, making it an alternative to writing "var = false;"
// or "var = oldVal;" at all of a block's exit points.
//
// This should be obvious, but note that an SetForScope<> instance should have a
// shorter lifetime than its scopedVariable, to prevent invalid memory writes
// when the SetForScope<> object is destroyed.
template<typename T>
class SetForScope {
WTF_MAKE_FAST_ALLOCATED;
WTF_MAKE_NONCOPYABLE(SetForScope);
public:
SetForScope(T& scopedVariable)
: m_scopedVariable(scopedVariable)
, m_valueToRestore(scopedVariable)
{
}
template<typename U>
SetForScope(T& scopedVariable, U&& newValue)
: SetForScope(scopedVariable)
{
m_scopedVariable = std::forward<U>(newValue);
}
template<typename U, typename V>
SetForScope(T& scopedVariable, U&& newValue, V&& restoreValue)
: m_scopedVariable(scopedVariable)
, m_valueToRestore(std::forward<V>(restoreValue))
{
m_scopedVariable = std::forward<U>(newValue);
}
~SetForScope()
{
m_scopedVariable = WTFMove(m_valueToRestore);
}
private:
T& m_scopedVariable;
T m_valueToRestore;
};
}
using WTF::SetForScope;
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