/*
* Copyright (C) 2013 Google Inc. All rights reserved.
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* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
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* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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*/
#ifndef UnsafePersistent_h
#define UnsafePersistent_h
#include "bindings/v8/WrapperTypeInfo.h"
#include <v8.h>
namespace WebCore {
template<class KeyType> class DOMWrapperMap;
// An unsafe way to pass Persistent handles around. Do not use unless you know
// what you're doing. UnsafePersistent is only safe to use when we know that the
// memory pointed by the it is not going away: 1) When GC cannot happen while
// the UnsafePersistent is alive or 2) when there is a strong Persistent keeping
// the memory alive while the UnsafePersistent is alive.
template<typename T> class UnsafePersistent {
public:
UnsafePersistent() : m_value(0) { }
explicit UnsafePersistent(T* value) : m_value(value) { }
explicit UnsafePersistent(v8::Persistent<T>& handle)
{
m_value = handle.ClearAndLeak();
}
UnsafePersistent(v8::Isolate* isolate, v8::Handle<T>& handle)
{
v8::Persistent<T> persistent(isolate, handle);
m_value = persistent.ClearAndLeak();
}
T* value() const
{
return m_value;
}
template<typename V8T, typename U>
inline bool setReturnValueWithSecurityCheck(v8::ReturnValue<v8::Value> returnValue, U* object)
{
// Security: always guard against malicious tampering.
RELEASE_ASSERT_WITH_SECURITY_IMPLICATION(isEmpty() || value()->GetAlignedPointerFromInternalField(v8DOMWrapperObjectIndex) == V8T::toInternalPointer(object));
returnValue.Set(*persistent());
return !isEmpty();
}
inline bool setReturnValue(v8::ReturnValue<v8::Value> returnValue)
{
returnValue.Set(*persistent());
return !isEmpty();
}
// This is incredibly unsafe: the handle is valid only when this
// UnsafePersistent is alive and valid (see class level comment).
v8::Persistent<T>* persistent()
{
v8::Persistent<T>* handle = reinterpret_cast<v8::Persistent<T>*>(&m_value);
return handle;
}
void setReferenceFrom(const v8::Persistent<v8::Object>& parent, v8::Isolate* isolate)
{
isolate->SetReference(parent, *persistent());
}
void dispose()
{
persistent()->Reset();
m_value = 0;
}
void clear()
{
m_value = 0;
}
v8::Local<T> newLocal(v8::Isolate* isolate)
{
return v8::Local<T>::New(isolate, *persistent());
}
bool isEmpty() const
{
return !m_value;
}
private:
T* m_value;
};
} // namespace WebCore
#endif // UnsafePersistent_h