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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 Handle_h
#define Handle_h
#include "WriteBarrier.h"
#include <wtf/Assertions.h>
namespace JSC {
/*
A Handle is a smart pointer that updates automatically when the garbage
collector moves the object to which it points.
The base Handle class represents a temporary reference to a pointer whose
lifetime is guaranteed by something else.
*/
template <class T> class Handle;
// Creating a JSValue Handle is invalid
template <> class Handle<JSValue>;
class HandleBase {
friend class HandleHeap;
public:
bool operator!() const { return isEmpty(); }
// This conversion operator allows implicit conversion to bool but not to other integer types.
typedef JSValue (HandleBase::*UnspecifiedBoolType);
operator UnspecifiedBoolType*() const { return (m_slot && *m_slot) ? reinterpret_cast<UnspecifiedBoolType*>(1) : 0; }
bool isEmpty() const { return !m_slot || !*m_slot; }
protected:
HandleBase(HandleSlot slot)
: m_slot(slot)
{
ASSERT(slot);
}
enum DontNullCheckSlotTag { DontNullCheckSlot };
HandleBase(HandleSlot slot, DontNullCheckSlotTag)
: m_slot(slot)
{
}
HandleSlot slot() const { return m_slot; }
void invalidate()
{
// It is unsafe to use a handle after invalidating it.
m_slot = 0;
}
// needed by Global<>::operator= and Global<>::set if it's an empty handle
void setSlot(HandleSlot slot)
{
ASSERT(!m_slot);
ASSERT(slot);
m_slot = slot;
}
private:
HandleSlot m_slot;
};
template <typename T> struct HandleTypes {
typedef T* ExternalType;
static ExternalType getFromSlot(HandleSlot slot) { return (slot && *slot) ? reinterpret_cast<ExternalType>(slot->asCell()) : 0; }
static JSValue toJSValue(T* cell) { return reinterpret_cast<JSCell*>(cell); }
template <typename U> static void validateUpcast() { T* temp; temp = (U*)0; }
};
template <> struct HandleTypes<Unknown> {
typedef JSValue ExternalType;
static ExternalType getFromSlot(HandleSlot slot) { return slot ? *slot : JSValue(); }
static JSValue toJSValue(const JSValue& v) { return v; }
template <typename U> static void validateUpcast() {}
};
template <typename Base, typename T> struct HandleConverter {
T* operator->() { return static_cast<Base*>(this)->get(); }
const T* operator->() const { return static_cast<const Base*>(this)->get(); }
T* operator*() { return static_cast<Base*>(this)->get(); }
const T* operator*() const { return static_cast<const Base*>(this)->get(); }
};
template <typename Base> struct HandleConverter<Base, Unknown> {
};
template <typename T> class Handle : public HandleBase, public HandleConverter<Handle<T>, T> {
public:
typedef typename HandleTypes<T>::ExternalType ExternalType;
template <typename U> Handle(Handle<U> o)
{
typename HandleTypes<T>::template validateUpcast<U>();
m_slot = o.slot();
}
ExternalType get() const { return HandleTypes<T>::getFromSlot(this->slot()); }
protected:
Handle(HandleSlot slot)
: HandleBase(slot)
{
}
Handle(HandleSlot slot, HandleBase::DontNullCheckSlotTag)
: HandleBase(slot, HandleBase::DontNullCheckSlot)
{
}
private:
friend class HandleHeap;
static Handle<T> wrapSlot(HandleSlot slot)
{
return Handle<T>(slot);
}
};
template <typename T, typename U> inline bool operator==(const Handle<T>& a, const Handle<U>& b)
{
return a.get() == b.get();
}
template <typename T, typename U> inline bool operator==(const Handle<T>& a, U* b)
{
return a.get() == b;
}
template <typename T, typename U> inline bool operator==(T* a, const Handle<U>& b)
{
return a == b.get();
}
template <typename T, typename U> inline bool operator!=(const Handle<T>& a, const Handle<U>& b)
{
return a.get() != b.get();
}
template <typename T, typename U> inline bool operator!=(const Handle<T>& a, U* b)
{
return a.get() != b;
}
template <typename T, typename U> inline bool operator!=(T* a, const Handle<U>& b)
{
return a != b.get();
}
template <typename T, typename U> inline bool operator!=(const Handle<T>& a, JSValue b)
{
return a.get() != b;
}
template <typename T, typename U> inline bool operator!=(JSValue a, const Handle<U>& b)
{
return a != b.get();
}
}
#endif
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