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/*
* Copyright (C) 2011 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.
*/
#ifndef Strong_h
#define Strong_h
#include <wtf/Assertions.h>
#include "Handle.h"
#include "HandleSet.h"
namespace JSC {
class VM;
// A strongly referenced handle that prevents the object it points to from being garbage collected.
template <typename T> class Strong : public Handle<T> {
using Handle<T>::slot;
using Handle<T>::setSlot;
template <typename U> friend class Strong;
public:
typedef typename Handle<T>::ExternalType ExternalType;
Strong()
: Handle<T>()
{
}
Strong(VM&, ExternalType = ExternalType());
Strong(VM&, Handle<T>);
Strong(const Strong& other)
: Handle<T>()
{
if (!other.slot())
return;
setSlot(HandleSet::heapFor(other.slot())->allocate());
set(other.get());
}
template <typename U> Strong(const Strong<U>& other)
: Handle<T>()
{
if (!other.slot())
return;
setSlot(HandleSet::heapFor(other.slot())->allocate());
set(other.get());
}
enum HashTableDeletedValueTag { HashTableDeletedValue };
bool isHashTableDeletedValue() const { return slot() == hashTableDeletedValue(); }
Strong(HashTableDeletedValueTag)
: Handle<T>(hashTableDeletedValue())
{
}
~Strong()
{
clear();
}
bool operator!() const { return !slot() || !*slot(); }
// This conversion operator allows implicit conversion to bool but not to other integer types.
typedef JSValue (HandleBase::*UnspecifiedBoolType);
operator UnspecifiedBoolType*() const { return !!*this ? reinterpret_cast<UnspecifiedBoolType*>(1) : 0; }
void swap(Strong& other)
{
Handle<T>::swap(other);
}
ExternalType get() const { return HandleTypes<T>::getFromSlot(this->slot()); }
void set(VM&, ExternalType);
template <typename U> Strong& operator=(const Strong<U>& other)
{
if (!other.slot()) {
clear();
return *this;
}
set(*HandleSet::heapFor(other.slot())->vm(), other.get());
return *this;
}
Strong& operator=(const Strong& other)
{
if (!other.slot()) {
clear();
return *this;
}
set(*HandleSet::heapFor(other.slot())->vm(), other.get());
return *this;
}
void clear()
{
if (!slot())
return;
HandleSet::heapFor(slot())->deallocate(slot());
setSlot(0);
}
private:
static HandleSlot hashTableDeletedValue() { return reinterpret_cast<HandleSlot>(-1); }
void set(ExternalType externalType)
{
ASSERT(slot());
JSValue value = HandleTypes<T>::toJSValue(externalType);
HandleSet::heapFor(slot())->writeBarrier(slot(), value);
*slot() = value;
}
};
template<class T> inline void swap(Strong<T>& a, Strong<T>& b)
{
a.swap(b);
}
} // namespace JSC
namespace WTF {
template<typename T> struct VectorTraits<JSC::Strong<T> > : SimpleClassVectorTraits {
static const bool canCompareWithMemcmp = false;
};
template<typename P> struct HashTraits<JSC::Strong<P> > : SimpleClassHashTraits<JSC::Strong<P> > { };
}
#endif // Strong_h
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