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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 WriteBarrier_h
#define WriteBarrier_h
#include "GCAssertions.h"
#include "HandleTypes.h"
#include "Heap.h"
#include "SamplingCounter.h"
#include <wtf/TypeTraits.h>
namespace JSC {
class JSCell;
class JSGlobalData;
class JSGlobalObject;
template<class T> class WriteBarrierBase;
template<> class WriteBarrierBase<JSValue>;
JS_EXPORT_PRIVATE void slowValidateCell(JSCell*);
JS_EXPORT_PRIVATE void slowValidateCell(JSGlobalObject*);
#if ENABLE(GC_VALIDATION)
template<class T> inline void validateCell(T cell)
{
ASSERT_GC_OBJECT_INHERITS(cell, WTF::RemovePointer<T>::Type::s_classinfo());
}
template<> inline void validateCell<JSCell*>(JSCell* cell)
{
slowValidateCell(cell);
}
template<> inline void validateCell<JSGlobalObject*>(JSGlobalObject* globalObject)
{
slowValidateCell(globalObject);
}
#else
template<class T> inline void validateCell(T)
{
}
#endif
// We have a separate base class with no constructors for use in Unions.
template <typename T> class WriteBarrierBase {
public:
void set(JSGlobalData& globalData, const JSCell* owner, T* value)
{
ASSERT(value);
validateCell(value);
setEarlyValue(globalData, owner, value);
}
// This is meant to be used like operator=, but is called copyFrom instead, in
// order to kindly inform the C++ compiler that its advice is not appreciated.
void copyFrom(const WriteBarrierBase<T>& other)
{
m_cell = other.m_cell;
}
void setMayBeNull(JSGlobalData& globalData, const JSCell* owner, T* value)
{
if (value)
validateCell(value);
setEarlyValue(globalData, owner, value);
}
// Should only be used by JSCell during early initialisation
// when some basic types aren't yet completely instantiated
void setEarlyValue(JSGlobalData&, const JSCell* owner, T* value)
{
this->m_cell = reinterpret_cast<JSCell*>(value);
Heap::writeBarrier(owner, this->m_cell);
}
T* get() const
{
if (m_cell)
validateCell(m_cell);
return reinterpret_cast<T*>(static_cast<void*>(m_cell));
}
T* operator*() const
{
ASSERT(m_cell);
validateCell<T>(static_cast<T*>(m_cell));
return static_cast<T*>(m_cell);
}
T* operator->() const
{
ASSERT(m_cell);
validateCell(static_cast<T*>(m_cell));
return static_cast<T*>(m_cell);
}
void clear() { m_cell = 0; }
JSCell** slot() { return &m_cell; }
typedef T* (WriteBarrierBase::*UnspecifiedBoolType);
operator UnspecifiedBoolType*() const { return m_cell ? reinterpret_cast<UnspecifiedBoolType*>(1) : 0; }
bool operator!() const { return !m_cell; }
void setWithoutWriteBarrier(T* value)
{
#if ENABLE(WRITE_BARRIER_PROFILING)
WriteBarrierCounters::usesWithoutBarrierFromCpp.count();
#endif
this->m_cell = reinterpret_cast<JSCell*>(value);
}
#if ENABLE(GC_VALIDATION)
T* unvalidatedGet() const { return reinterpret_cast<T*>(static_cast<void*>(m_cell)); }
#endif
private:
JSCell* m_cell;
};
template <> class WriteBarrierBase<Unknown> {
public:
void set(JSGlobalData&, const JSCell* owner, JSValue value)
{
m_value = JSValue::encode(value);
Heap::writeBarrier(owner, value);
}
void setWithoutWriteBarrier(JSValue value)
{
m_value = JSValue::encode(value);
}
JSValue get() const
{
return JSValue::decode(m_value);
}
void clear() { m_value = JSValue::encode(JSValue()); }
void setUndefined() { m_value = JSValue::encode(jsUndefined()); }
bool isNumber() const { return get().isNumber(); }
bool isObject() const { return get().isObject(); }
bool isNull() const { return get().isNull(); }
bool isGetterSetter() const { return get().isGetterSetter(); }
JSValue* slot()
{
union {
EncodedJSValue* v;
JSValue* slot;
} u;
u.v = &m_value;
return u.slot;
}
int32_t* tagPointer() { return &bitwise_cast<EncodedValueDescriptor*>(&m_value)->asBits.tag; }
int32_t* payloadPointer() { return &bitwise_cast<EncodedValueDescriptor*>(&m_value)->asBits.payload; }
typedef JSValue (WriteBarrierBase::*UnspecifiedBoolType);
operator UnspecifiedBoolType*() const { return get() ? reinterpret_cast<UnspecifiedBoolType*>(1) : 0; }
bool operator!() const { return !get(); }
private:
EncodedJSValue m_value;
};
template <typename T> class WriteBarrier : public WriteBarrierBase<T> {
public:
WriteBarrier()
{
this->setWithoutWriteBarrier(0);
}
WriteBarrier(JSGlobalData& globalData, const JSCell* owner, T* value)
{
this->set(globalData, owner, value);
}
enum MayBeNullTag { MayBeNull };
WriteBarrier(JSGlobalData& globalData, const JSCell* owner, T* value, MayBeNullTag)
{
this->setMayBeNull(globalData, owner, value);
}
};
template <> class WriteBarrier<Unknown> : public WriteBarrierBase<Unknown> {
public:
WriteBarrier()
{
this->setWithoutWriteBarrier(JSValue());
}
WriteBarrier(JSGlobalData& globalData, const JSCell* owner, JSValue value)
{
this->set(globalData, owner, value);
}
};
template <typename U, typename V> inline bool operator==(const WriteBarrierBase<U>& lhs, const WriteBarrierBase<V>& rhs)
{
return lhs.get() == rhs.get();
}
// SlotVisitor functions
template<typename T> inline void SlotVisitor::append(WriteBarrierBase<T>* slot)
{
internalAppend(*slot->slot());
}
ALWAYS_INLINE void SlotVisitor::appendValues(WriteBarrierBase<Unknown>* barriers, size_t count)
{
append(barriers->slot(), count);
}
} // namespace JSC
#endif // WriteBarrier_h