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