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/*
* Copyright (C) 2018-2024 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. AND ITS CONTRIBUTORS ``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 ITS 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 "DOMWrapperWorld.h"
#include "JSDOMWrapper.h"
#include <JavaScriptCore/JSCJSValueInlines.h>
#include <JavaScriptCore/SlotVisitor.h>
#include <JavaScriptCore/WeakInlines.h>
#include <variant>
namespace WebCore {
// This class includes a lot of subtle GC related things, and changing this class can easily cause GC crashes.
// Any changes to this class must be reviewed by JavaScriptCore reviewers too.
class JSValueInWrappedObject {
// This must be neither copyable nor movable. Changing this will break concurrent GC.
WTF_MAKE_NONCOPYABLE(JSValueInWrappedObject);
WTF_MAKE_NONMOVABLE(JSValueInWrappedObject);
public:
JSValueInWrappedObject(JSC::JSValue = { });
explicit operator bool() const;
template<typename Visitor> void visit(Visitor&) const;
void clear();
// If you expect the value you store to be returned by getValue and not cleared under you, you *MUST* use set not setWeakly.
// The owner parameter is typically the wrapper of the DOM node this class is embedded into but can be any GCed object that
// will visit this JSValueInWrappedObject via visitAdditionalChildren/isReachableFromOpaqueRoots.
void set(JSC::VM&, const JSC::JSCell* owner, JSC::JSValue);
// Only use this if you actually expect this value to be weakly held. If you call visit on this value *DONT* set using setWeakly
// use set instead. The GC might or might not keep your value around in that case.
void setWeakly(JSC::JSValue);
JSC::JSValue getValue(JSC::JSValue nullValue = JSC::jsUndefined()) const;
private:
// Keep in mind that all of these fields are accessed concurrently without lock from concurrent GC thread.
JSC::JSValue m_nonCell { };
JSC::Weak<JSC::JSCell> m_cell { };
};
JSC::JSValue cachedPropertyValue(JSC::ThrowScope&, JSC::JSGlobalObject&, const JSDOMObject& owner, JSValueInWrappedObject& cacheSlot, const auto&);
inline JSValueInWrappedObject::JSValueInWrappedObject(JSC::JSValue value)
{
setWeakly(value);
}
inline JSC::JSValue JSValueInWrappedObject::getValue(JSC::JSValue nullValue) const
{
if (m_nonCell)
return m_nonCell;
return m_cell ? m_cell.get() : nullValue;
}
inline JSValueInWrappedObject::operator bool() const
{
return m_nonCell || m_cell;
}
template<typename Visitor>
inline void JSValueInWrappedObject::visit(Visitor& visitor) const
{
visitor.append(m_cell);
}
template void JSValueInWrappedObject::visit(JSC::AbstractSlotVisitor&) const;
template void JSValueInWrappedObject::visit(JSC::SlotVisitor&) const;
inline void JSValueInWrappedObject::setWeakly(JSC::JSValue value)
{
if (!value.isCell()) {
m_nonCell = value;
m_cell.clear();
return;
}
m_nonCell = { };
JSC::Weak weak { value.asCell() };
WTF::storeStoreFence();
m_cell = WTFMove(weak);
}
inline void JSValueInWrappedObject::set(JSC::VM& vm, const JSC::JSCell* owner, JSC::JSValue value)
{
setWeakly(value);
vm.writeBarrier(owner, value);
}
inline void JSValueInWrappedObject::clear()
{
m_nonCell = { };
m_cell.clear();
}
inline JSC::JSValue cachedPropertyValue(JSC::ThrowScope& throwScope, JSC::JSGlobalObject& lexicalGlobalObject, const JSDOMObject& owner, JSValueInWrappedObject& cachedValue, const auto& function)
{
if (cachedValue && isWorldCompatible(lexicalGlobalObject, cachedValue.getValue()))
return cachedValue.getValue();
auto value = function(throwScope);
RETURN_IF_EXCEPTION(throwScope, { });
cachedValue.set(lexicalGlobalObject.vm(), &owner, cloneAcrossWorlds(lexicalGlobalObject, owner, value));
ASSERT(isWorldCompatible(lexicalGlobalObject, cachedValue.getValue()));
return cachedValue.getValue();
}
} // namespace WebCore
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