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/*
* Copyright (C) 2019 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 "JSProxy.h"
namespace JSC {
class JSNonDestructibleProxy : public JSProxy {
public:
using Base = JSProxy;
static const unsigned StructureFlags = Base::StructureFlags;
static const bool needsDestruction = false;
template<typename CellType, SubspaceAccess mode>
static CompleteSubspace* subspaceFor(VM& vm)
{
// JSProxy is JSDestrucitbleObject, but we make this JSNonDestructibleProxy non-destructible by using non-destructible subspace.
// The motivation behind this is (1) except for JSWindowProxy JSProxy does not need to be destructible, and (2) subspace of destructible
// and non-destructible objects are separated and JSProxy is using one MarkedBlock only for JSProxy class in the JSC framework and wasting memory.
// Basically, to make objects destructible, objects need to inherit JSDestructibleObject. It holds a classInfo at a specific offset
// so that Heap can get methodTable::destroy even if structures held by objects are destroyed before objects' destructions. But this
// requirement forces JSProxy to inherit JSDestructibleObject for JSWindowProxy even while the other JSProxy does not need to be
// destructible. We create JSNonDestructibleProxy, which is a subclass of JSProxy, and make it non-destructible so that we still keep
// JSWindowProxy destructible while making JSNonDestructibleProxy non-destructible.
return JSNonFinalObject::subspaceFor<CellType, mode>(vm);
}
static JSNonDestructibleProxy* create(VM& vm, Structure* structure, JSObject* target)
{
JSNonDestructibleProxy* proxy = new (NotNull, allocateCell<JSNonDestructibleProxy>(vm.heap)) JSNonDestructibleProxy(vm, structure);
proxy->finishCreation(vm, target);
return proxy;
}
static JSNonDestructibleProxy* create(VM& vm, Structure* structure)
{
JSNonDestructibleProxy* proxy = new (NotNull, allocateCell<JSNonDestructibleProxy>(vm.heap)) JSNonDestructibleProxy(vm, structure);
proxy->finishCreation(vm);
return proxy;
}
static Structure* createStructure(VM& vm, JSGlobalObject* globalObject, JSValue prototype, JSType proxyType)
{
ASSERT(proxyType == ImpureProxyType || proxyType == PureForwardingProxyType);
return Structure::create(vm, globalObject, prototype, TypeInfo(proxyType, StructureFlags), info());
}
DECLARE_EXPORT_INFO;
protected:
JSNonDestructibleProxy(VM& vm, Structure* structure)
: Base(vm, structure)
{
}
};
} // namespace JSC