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26 #ifndef WriteBarrier_h
27 #define WriteBarrier_h
29 #include "HandleTypes.h"
31 #include "SamplingCounter.h"
32 #include "TypeTraits.h"
40 template<class T> class WriteBarrierBase;
41 template<> class WriteBarrierBase<JSValue>;
43 void slowValidateCell(JSCell*);
44 void slowValidateCell(JSGlobalObject*);
46 #if ENABLE(GC_VALIDATION)
47 template<class T> inline void validateCell(T cell)
49 ASSERT_GC_OBJECT_INHERITS(cell, &WTF::RemovePointer<T>::Type::s_info);
52 template<> inline void validateCell<JSCell*>(JSCell* cell)
54 slowValidateCell(cell);
57 template<> inline void validateCell<JSGlobalObject*>(JSGlobalObject* globalObject)
59 slowValidateCell(globalObject);
62 template<class T> inline void validateCell(T)
67 // We have a separate base class with no constructors for use in Unions.
68 template <typename T> class WriteBarrierBase {
70 void set(JSGlobalData& globalData, const JSCell* owner, T* value)
74 setEarlyValue(globalData, owner, value);
77 void setMayBeNull(JSGlobalData& globalData, const JSCell* owner, T* value)
81 setEarlyValue(globalData, owner, value);
84 // Should only be used by JSCell during early initialisation
85 // when some basic types aren't yet completely instantiated
86 void setEarlyValue(JSGlobalData&, const JSCell* owner, T* value)
88 this->m_cell = reinterpret_cast<JSCell*>(value);
89 Heap::writeBarrier(owner, this->m_cell);
96 return reinterpret_cast<T*>(m_cell);
102 validateCell<T>(static_cast<T*>(m_cell));
103 return static_cast<T*>(m_cell);
106 T* operator->() const
109 validateCell(static_cast<T*>(m_cell));
110 return static_cast<T*>(m_cell);
113 void clear() { m_cell = 0; }
115 JSCell** slot() { return &m_cell; }
117 typedef T* (WriteBarrierBase::*UnspecifiedBoolType);
118 operator UnspecifiedBoolType*() const { return m_cell ? reinterpret_cast<UnspecifiedBoolType*>(1) : 0; }
120 bool operator!() const { return !m_cell; }
122 void setWithoutWriteBarrier(T* value)
124 #if ENABLE(WRITE_BARRIER_PROFILING)
125 WriteBarrierCounters::usesWithoutBarrierFromCpp.count();
127 this->m_cell = reinterpret_cast<JSCell*>(value);
130 #if ENABLE(GC_VALIDATION)
131 T* unvalidatedGet() const { return reinterpret_cast<T*>(m_cell); }
138 template <> class WriteBarrierBase<Unknown> {
140 void set(JSGlobalData&, const JSCell* owner, JSValue value)
142 m_value = JSValue::encode(value);
143 Heap::writeBarrier(owner, value);
146 void setWithoutWriteBarrier(JSValue value)
148 m_value = JSValue::encode(value);
153 return JSValue::decode(m_value);
155 void clear() { m_value = JSValue::encode(JSValue()); }
156 void setUndefined() { m_value = JSValue::encode(jsUndefined()); }
157 bool isNumber() const { return get().isNumber(); }
158 bool isObject() const { return get().isObject(); }
159 bool isNull() const { return get().isNull(); }
160 bool isGetterSetter() const { return get().isGetterSetter(); }
172 typedef JSValue (WriteBarrierBase::*UnspecifiedBoolType);
173 operator UnspecifiedBoolType*() const { return get() ? reinterpret_cast<UnspecifiedBoolType*>(1) : 0; }
174 bool operator!() const { return !get(); }
177 EncodedJSValue m_value;
180 template <typename T> class WriteBarrier : public WriteBarrierBase<T> {
184 this->setWithoutWriteBarrier(0);
187 WriteBarrier(JSGlobalData& globalData, const JSCell* owner, T* value)
189 this->set(globalData, owner, value);
192 enum MayBeNullTag { MayBeNull };
193 WriteBarrier(JSGlobalData& globalData, const JSCell* owner, T* value, MayBeNullTag)
195 this->setMayBeNull(globalData, owner, value);
199 template <> class WriteBarrier<Unknown> : public WriteBarrierBase<Unknown> {
203 this->setWithoutWriteBarrier(JSValue());
206 WriteBarrier(JSGlobalData& globalData, const JSCell* owner, JSValue value)
208 this->set(globalData, owner, value);
212 template <typename U, typename V> inline bool operator==(const WriteBarrierBase<U>& lhs, const WriteBarrierBase<V>& rhs)
214 return lhs.get() == rhs.get();
217 // MarkStack functions
219 template<typename T> inline void MarkStack::append(WriteBarrierBase<T>* slot)
221 internalAppend(*slot->slot());
224 ALWAYS_INLINE void MarkStack::appendValues(WriteBarrierBase<Unknown>* barriers, size_t count)
226 append(barriers->slot(), count);
231 #endif // WriteBarrier_h