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a/Source/WTF/wtf/NeverDestroyed.h_sec1
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/* |
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* Copyright (C) 2013 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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* 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 INC. AND ITS CONTRIBUTORS ``AS IS'' |
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, |
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS |
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF |
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* THE POSSIBILITY OF SUCH DAMAGE. |
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*/ |
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#ifndef NeverDestroyed_h |
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#define NeverDestroyed_h |
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#include <wtf/Alignment.h> |
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#include <wtf/Noncopyable.h> |
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#include <wtf/StdLibExtras.h> |
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#include <wtf/TypeTraits.h> |
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// NeverDestroyed is a smart pointer like class who ensures that the destructor |
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// for the given object is never called, but doesn't use the heap to allocate it. |
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// It's useful for static local variables, and can be used like so: |
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// |
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// MySharedGlobal& mySharedGlobal() |
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// { |
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// static NeverDestroyed<MySharedGlobal> myGlobal("Hello", 42); |
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// return myGlobal; |
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// } |
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// |
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namespace WTF { |
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template<typename T> class NeverDestroyed { |
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WTF_MAKE_NONCOPYABLE(NeverDestroyed); |
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public: |
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#if COMPILER_SUPPORTS(CXX_VARIADIC_TEMPLATES) |
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template<typename... Args> |
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NeverDestroyed(Args&&... args) |
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{ |
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new (asPtr()) T(std::forward<Args>(args)...); |
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} |
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#else |
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NeverDestroyed() |
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{ |
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new (NotNull, asPtr()) T; |
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} |
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template<typename P1> |
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NeverDestroyed(const P1& p1) |
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{ |
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new (NotNull, asPtr()) T(p1); |
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} |
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#endif |
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operator T&() { return *asPtr(); } |
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private: |
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#if COMPILER_SUPPORTS(CXX_RVALUE_REFERENCES) |
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NeverDestroyed(NeverDestroyed&&) WTF_DELETED_FUNCTION; |
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#endif |
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typedef typename WTF::RemoveConst<T>::Type *PointerType; |
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PointerType asPtr() { return reinterpret_cast<PointerType>(&m_storage); } |
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// FIXME: Investigate whether we should allocate a hunk of virtual memory |
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// and hand out chunks of it to NeverDestroyed instead, to reduce fragmentation. |
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AlignedBuffer<sizeof(T), WTF_ALIGN_OF(T)> m_storage; |
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}; |
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} // namespace WTF; |
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using WTF::NeverDestroyed; |
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#endif // NeverDestroyed_h |