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/*
* Copyright (C) 2019-2022 Apple, 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 INC. ``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 INC. OR
* 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.
*/
#pragma once
#include "JSObject.h"
namespace JSC {
class JSWeakObjectRef final : public JSNonFinalObject {
public:
using Base = JSNonFinalObject;
DECLARE_EXPORT_INFO;
inline static Structure* createStructure(VM&, JSGlobalObject*, JSValue);
static JSWeakObjectRef* create(VM& vm, Structure* structure, JSCell* target)
{
JSWeakObjectRef* instance = new (NotNull, allocateCell<JSWeakObjectRef>(vm)) JSWeakObjectRef(vm, structure);
instance->finishCreation(vm, target);
return instance;
}
JSCell* deref(VM& vm)
{
if (m_value && vm.currentWeakRefVersion() != m_lastAccessVersion) {
m_lastAccessVersion = vm.currentWeakRefVersion();
// Perform a GC barrier here so we rescan this object and keep the object alive if we wouldn't otherwise.
vm.writeBarrier(this);
}
return m_value.get();
}
template<typename CellType, SubspaceAccess mode>
static GCClient::IsoSubspace* subspaceFor(VM& vm)
{
return vm.weakObjectRefSpace<mode>();
}
void finalizeUnconditionally(VM&, CollectionScope);
DECLARE_VISIT_CHILDREN;
private:
JSWeakObjectRef(VM& vm, Structure* structure)
: Base(vm, structure)
{
}
JS_EXPORT_PRIVATE void finishCreation(VM&, JSCell* value);
uintptr_t m_lastAccessVersion;
WriteBarrier<JSCell> m_value;
};
} // namespace JSC
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