121 lines
3.3 KiB
C++
121 lines
3.3 KiB
C++
/*
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* Copyright (C) 2013-2019 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. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* 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
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* OF 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/Assertions.h>
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#include <wtf/FastMalloc.h>
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#include <wtf/Noncopyable.h>
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namespace WTF {
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// A variant of RefCounted that allows reference counting to be deferred,
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// and can tell you if that has happened. You can think of a deferral as
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// just being an additional "ref", except that you can detect if it has
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// specifically happened - this can be useful either for debugging, or
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// sometimes even for some additional functionality.
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class DeferrableRefCountedBase {
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static constexpr unsigned deferredFlag = 1;
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static constexpr unsigned normalIncrement = 2;
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public:
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void ref() const
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{
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m_refCount += normalIncrement;
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}
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bool hasOneRef() const
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{
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return refCount() == 1;
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}
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unsigned refCount() const
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{
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return m_refCount / normalIncrement;
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}
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bool isDeferred() const
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{
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return !!(m_refCount & deferredFlag);
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}
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protected:
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DeferrableRefCountedBase()
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: m_refCount(normalIncrement)
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{
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}
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~DeferrableRefCountedBase()
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{
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}
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bool derefBase() const
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{
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m_refCount -= normalIncrement;
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return !m_refCount;
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}
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bool setIsDeferredBase(bool value)
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{
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if (value) {
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m_refCount |= deferredFlag;
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return false;
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}
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m_refCount &= ~deferredFlag;
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return !m_refCount;
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}
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private:
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mutable unsigned m_refCount;
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};
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template<typename T>
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class DeferrableRefCounted : public DeferrableRefCountedBase {
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WTF_MAKE_NONCOPYABLE(DeferrableRefCounted); WTF_MAKE_FAST_ALLOCATED;
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public:
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void deref() const
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{
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if (derefBase())
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delete static_cast<const T*>(this);
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}
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bool setIsDeferred(bool value)
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{
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if (!setIsDeferredBase(value))
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return false;
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delete static_cast<T*>(this);
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return true;
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}
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protected:
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DeferrableRefCounted() { }
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~DeferrableRefCounted() { }
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};
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} // namespace WTF
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using WTF::DeferrableRefCounted;
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