/*
* 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:
*
* 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.
*/
#ifndef TemporaryChange_h
#define TemporaryChange_h
#include "wtf/Noncopyable.h"
namespace WTF {
// TemporaryChange<> is useful for setting a variable to a new value only within a
// particular scope. An TemporaryChange<> 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 TemporaryChange<> instance should have a
// shorter lifetime than its scopedVariable, to prevent invalid memory writes
// when the TemporaryChange<> object is destroyed.
template<typename T>
class TemporaryChange {
WTF_MAKE_NONCOPYABLE(TemporaryChange);
public:
TemporaryChange(T& scopedVariable, T newValue)
: m_scopedVariable(scopedVariable)
, m_originalValue(scopedVariable)
{
m_scopedVariable = newValue;
}
~TemporaryChange()
{
m_scopedVariable = m_originalValue;
}
private:
T& m_scopedVariable;
T m_originalValue;
};
}
using WTF::TemporaryChange;
#endif