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/*
* Copyright (C) 2009, 2012 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 Weak_h
#define Weak_h
#include "Assertions.h"
#include "Handle.h"
#include "HandleHeap.h"
#include "JSGlobalData.h"
#include "PassWeak.h"
namespace JSC {
// A weakly referenced handle that becomes 0 when the value it points to is garbage collected.
template <typename T> class Weak : public Handle<T> {
WTF_MAKE_NONCOPYABLE(Weak);
using Handle<T>::slot;
using Handle<T>::setSlot;
public:
typedef typename Handle<T>::ExternalType ExternalType;
Weak()
: Handle<T>()
{
}
Weak(std::nullptr_t)
: Handle<T>()
{
}
Weak(JSGlobalData& globalData, ExternalType externalType = ExternalType(), WeakHandleOwner* weakOwner = 0, void* context = 0)
: Handle<T>(globalData.heap.handleHeap()->allocate())
{
HandleHeap::heapFor(slot())->makeWeak(slot(), weakOwner, context);
JSValue value = HandleTypes<T>::toJSValue(externalType);
HandleHeap::heapFor(slot())->writeBarrier(slot(), value);
*slot() = value;
}
enum AdoptTag { Adopt };
template<typename U> Weak(AdoptTag, Handle<U> handle)
: Handle<T>(handle.slot())
{
validateCell(get());
}
enum HashTableDeletedValueTag { HashTableDeletedValue };
bool isHashTableDeletedValue() const { return slot() == hashTableDeletedValue(); }
Weak(HashTableDeletedValueTag)
: Handle<T>(hashTableDeletedValue())
{
}
template<typename U> Weak(const PassWeak<U>& other)
: Handle<T>(other.leakHandle())
{
}
~Weak()
{
clear();
}
void swap(Weak& other)
{
Handle<T>::swap(other);
}
Weak& operator=(const PassWeak<T>&);
ExternalType get() const { return HandleTypes<T>::getFromSlot(slot()); }
PassWeak<T> release() { PassWeak<T> tmp = adoptWeak<T>(slot()); setSlot(0); return tmp; }
void clear()
{
if (!slot())
return;
HandleHeap::heapFor(slot())->deallocate(slot());
setSlot(0);
}
HandleSlot leakHandle()
{
ASSERT(HandleHeap::heapFor(slot())->hasFinalizer(slot()));
HandleSlot result = slot();
setSlot(0);
return result;
}
private:
static HandleSlot hashTableDeletedValue() { return reinterpret_cast<HandleSlot>(-1); }
};
template<class T> inline void swap(Weak<T>& a, Weak<T>& b)
{
a.swap(b);
}
template<typename T> inline Weak<T>& Weak<T>::operator=(const PassWeak<T>& o)
{
clear();
setSlot(o.leakHandle());
return *this;
}
} // namespace JSC
namespace WTF {
template<typename T> struct VectorTraits<JSC::Weak<T> > : SimpleClassVectorTraits {
static const bool canCompareWithMemcmp = false;
};
template<typename T> struct HashTraits<JSC::Weak<T> > : SimpleClassHashTraits<JSC::Weak<T> > {
typedef JSC::Weak<T> StorageType;
typedef std::nullptr_t EmptyValueType;
static EmptyValueType emptyValue() { return nullptr; }
typedef JSC::PassWeak<T> PassInType;
static void store(PassInType value, StorageType& storage) { storage = value; }
typedef JSC::PassWeak<T> PassOutType;
static PassOutType passOut(StorageType& value) { return value.release(); }
static PassOutType passOut(EmptyValueType) { return PassOutType(); }
typedef typename StorageType::ExternalType PeekType;
static PeekType peek(const StorageType& value) { return value.get(); }
static PeekType peek(EmptyValueType) { return PeekType(); }
};
}
#endif // Weak_h
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