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/*
* Copyright (C) 2018 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/JSCJSValue.h>
#include <JavaScriptCore/SlotVisitor.h>
#include <JavaScriptCore/Weak.h>
namespace WebCore {
class JSValueInWrappedObject {
public:
JSValueInWrappedObject(JSC::JSValue = { });
JSValueInWrappedObject(const JSValueInWrappedObject&);
operator JSC::JSValue() const;
explicit operator bool() const;
JSValueInWrappedObject& operator=(const JSValueInWrappedObject& other);
void visit(JSC::SlotVisitor&);
void clear();
private:
// Use a weak pointer here so that if this code or client code has a visiting mistake,
// we get null rather than a dangling pointer to a deleted object.
using Weak = JSC::Weak<JSC::JSCell>;
JSC::JSValue m_jsValue;
Weak m_weakValue;
bool m_isWeak;
};
inline JSValueInWrappedObject::JSValueInWrappedObject(JSC::JSValue value)
{
if (!value.isCell()) {
m_jsValue = value;
m_isWeak = false;
} else {
// FIXME: This is not quite right. It is possible that this value is being
// stored in a wrapped object that does not yet have a wrapper. If garbage
// collection occurs before the wrapped object gets a wrapper, it's possible
// the value object could be collected, and this will become null. A future
// version of this class should prevent the value from being collected in
// that case. Unclear if this can actually happen in practice.
m_weakValue = Weak { value.asCell() };
m_isWeak = true;
}
}
inline JSValueInWrappedObject::JSValueInWrappedObject(const JSValueInWrappedObject& other)
{
JSC::JSValue value = other;
if (!value.isCell()) {
m_jsValue = value;
m_isWeak = false;
} else {
// FIXME: This is not quite right. It is possible that this value is being
// stored in a wrapped object that does not yet have a wrapper. If garbage
// collection occurs before the wrapped object gets a wrapper, it's possible
// the value object could be collected, and this will become null. A future
// version of this class should prevent the value from being collected in
// that case. Unclear if this can actually happen in practice.
m_weakValue = Weak { value.asCell() };
m_isWeak = true;
}
}
inline JSValueInWrappedObject::operator JSC::JSValue() const
{
if (!m_isWeak)
return m_jsValue;
return m_weakValue.get();
}
inline JSValueInWrappedObject::operator bool() const
{
return JSC::JSValue { *this }.operator bool();
}
inline JSValueInWrappedObject& JSValueInWrappedObject::operator=(const JSValueInWrappedObject& other)
{
JSC::JSValue value = other;
if (!value.isCell()) {
m_jsValue = value;
m_isWeak = false;
} else {
// FIXME: This is not quite right. It is possible that this value is being
// stored in a wrapped object that does not yet have a wrapper. If garbage
// collection occurs before the wrapped object gets a wrapper, it's possible
// the value object could be collected, and this will become null. A future
// version of this class should prevent the value from being collected in
// that case. Unclear if this can actually happen in practice.
m_weakValue = Weak { value.asCell() };
m_isWeak = true;
}
return *this;
}
inline void JSValueInWrappedObject::visit(JSC::SlotVisitor& visitor)
{
if (!m_isWeak) {
// Nothing to visit.
} else {
visitor.appendUnbarrieredWeak(&m_weakValue);
};
}
inline void JSValueInWrappedObject::clear()
{
if (m_isWeak)
m_weakValue.clear();
}
} // namespace WebCore
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