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https://github.com/darlinghq/darling-WTF.git
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72 lines
2.5 KiB
C++
72 lines
2.5 KiB
C++
/*
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* Copyright (C) 2011 Google Inc. All rights reserved.
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* Copyright (C) 2016 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <wtf/Noncopyable.h>
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#include <wtf/StdLibExtras.h>
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namespace WTF {
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// SetForScope<> is useful for setting a variable to a new value only within a
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// particular scope. An SetForScope<> object changes a variable to its original
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// value upon destruction, making it an alternative to writing "var = false;"
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// or "var = oldVal;" at all of a block's exit points.
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//
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// This should be obvious, but note that an SetForScope<> instance should have a
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// shorter lifetime than its scopedVariable, to prevent invalid memory writes
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// when the SetForScope<> object is destroyed.
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template<typename T>
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class SetForScope {
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WTF_MAKE_NONCOPYABLE(SetForScope);
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public:
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SetForScope(T& scopedVariable)
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: m_scopedVariable(scopedVariable)
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, m_originalValue(scopedVariable)
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{
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}
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template<typename U>
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SetForScope(T& scopedVariable, U&& newValue)
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: SetForScope(scopedVariable)
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{
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m_scopedVariable = std::forward<U>(newValue);
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}
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~SetForScope()
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{
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m_scopedVariable = WTFMove(m_originalValue);
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}
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private:
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T& m_scopedVariable;
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T m_originalValue;
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};
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}
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using WTF::SetForScope;
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