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26 #ifndef Supplementable_h
27 #define Supplementable_h
29 #include "platform/heap/Handle.h"
30 #include "wtf/Assertions.h"
31 #include "wtf/HashMap.h"
32 #include "wtf/OwnPtr.h"
33 #include "wtf/PassOwnPtr.h"
36 #include "wtf/Threading.h"
41 // What you should know about Supplementable and Supplement
42 // ========================================================
43 // Supplementable and Supplement instances are meant to be thread local. They
44 // should only be accessed from within the thread that created them. The
45 // 2 classes are not designed for safe access from another thread. Violating
46 // this design assumption can result in memory corruption and unpredictable
49 // What you should know about the Supplement keys
50 // ==============================================
51 // The Supplement is expected to use the same const char* string instance
52 // as its key. The Supplementable's SupplementMap will use the address of the
53 // string as the key and not the characters themselves. Hence, 2 strings with
54 // the same characters will be treated as 2 different keys.
56 // In practice, it is recommended that Supplements implements a static method
57 // for returning its key to use. For example:
59 // class MyClass : public Supplement<MySupplementable> {
61 // static const char* supplementName();
64 // const char* MyClass::supplementName()
69 // An example of the using the key:
71 // MyClass* MyClass::from(MySupplementable* host)
73 // return reinterpret_cast<MyClass*>(Supplement<MySupplementable>::from(host, supplementName()));
76 // What you should know about thread checks
77 // ========================================
78 // When assertion is enabled this class performs thread-safety check so that
79 // provideTo and from happen on the same thread. If you want to provide
80 // some value for Workers this thread check may not work very well though,
81 // since in most case you'd provide the value while worker preparation is
82 // being done on the main thread, even before the worker thread is started.
83 // If that's the case you can explicitly call reattachThread() when the
84 // Supplementable object is passed to the final destination thread (i.e.
85 // worker thread). Please be extremely careful to use the method though,
86 // as randomly calling the method could easily cause racy condition.
88 // Note that reattachThread() does nothing if assertion is not enabled.
91 template<typename T, bool isGarbageCollected>
94 template<typename T, bool isGarbageCollected>
95 class SupplementableBase;
97 template<typename T, bool isGarbageCollected>
98 struct SupplementableTraits;
101 struct SupplementableTraits<T, true> {
102 typedef RawPtr<SupplementBase<T, true> > SupplementArgumentType;
103 typedef HeapHashMap<const char*, Member<SupplementBase<T, true> >, PtrHash<const char*> > SupplementMap;
107 struct SupplementableTraits<T, false> {
108 typedef PassOwnPtr<SupplementBase<T, false> > SupplementArgumentType;
109 typedef HashMap<const char*, OwnPtr<SupplementBase<T, false> >, PtrHash<const char*> > SupplementMap;
113 class SupplementTracing;
116 class SupplementTracing<true> : public GarbageCollectedMixin { };
119 class SupplementTracing<false> {
121 virtual ~SupplementTracing() { }
122 virtual void trace(Visitor*) { }
125 template<typename T, bool isGarbageCollected = false>
126 class SupplementBase : public SupplementTracing<isGarbageCollected> {
128 #if ENABLE(SECURITY_ASSERT)
129 virtual bool isRefCountedWrapper() const { return false; }
132 static void provideTo(SupplementableBase<T, isGarbageCollected>& host, const char* key, typename SupplementableTraits<T, isGarbageCollected>::SupplementArgumentType supplement)
134 host.provideSupplement(key, supplement);
137 static SupplementBase<T, isGarbageCollected>* from(SupplementableBase<T, isGarbageCollected>& host, const char* key)
139 return host.requireSupplement(key);
142 static SupplementBase<T, isGarbageCollected>* from(SupplementableBase<T, isGarbageCollected>* host, const char* key)
144 return host ? host->requireSupplement(key) : 0;
147 virtual void willBeDestroyed() { }
149 // FIXME: Oilpan: Remove this callback once PersistentHeapSupplementable is removed again.
150 virtual void persistentHostHasBeenDestroyed() { }
153 // Helper class for implementing Supplementable, HeapSupplementable, and
154 // PersistentHeapSupplementable.
155 template<typename T, bool isGarbageCollected = false>
156 class SupplementableBase {
158 void provideSupplement(const char* key, typename SupplementableTraits<T, isGarbageCollected>::SupplementArgumentType supplement)
160 ASSERT(m_threadId == currentThread());
161 ASSERT(!this->m_supplements.get(key));
162 this->m_supplements.set(key, supplement);
165 void removeSupplement(const char* key)
167 ASSERT(m_threadId == currentThread());
168 this->m_supplements.remove(key);
171 SupplementBase<T, isGarbageCollected>* requireSupplement(const char* key)
173 ASSERT(m_threadId == currentThread());
174 return this->m_supplements.get(key);
177 void reattachThread()
180 m_threadId = currentThread();
184 // We have a trace method in the SupplementableBase class to ensure we have
185 // the vtable at the first word of the object. However we don't trace the
186 // m_supplements here, but in the partially specialized template subclasses
187 // since we only want to trace it for garbage collected classes.
188 virtual void trace(Visitor*) { }
190 void willBeDestroyed()
192 typedef typename SupplementableTraits<T, isGarbageCollected>::SupplementMap::iterator SupplementIterator;
193 for (SupplementIterator it = m_supplements.begin(); it != m_supplements.end(); ++it)
194 it->value->willBeDestroyed();
197 // FIXME: Oilpan: Make private and remove this ignore once PersistentHeapSupplementable is removed again.
200 typename SupplementableTraits<T, isGarbageCollected>::SupplementMap m_supplements;
204 SupplementableBase() : m_threadId(currentThread()) { }
207 ThreadIdentifier m_threadId;
211 // This class is used to make an on-heap class supplementable. Its supplements
212 // must be HeapSupplement.
214 class HeapSupplement : public SupplementBase<T, true> { };
216 // FIXME: Oilpan: Move GarbageCollectedMixin to SupplementableBase<T, true> once PersistentHeapSupplementable is removed again.
218 class GC_PLUGIN_IGNORE("http://crbug.com/395036") HeapSupplementable : public SupplementableBase<T, true>, public GarbageCollectedMixin {
220 virtual void trace(Visitor* visitor) OVERRIDE
222 visitor->trace(this->m_supplements);
223 SupplementableBase<T, true>::trace(visitor);
227 // This class is used to make an off-heap class supplementable with supplements
228 // that are on-heap, aka. HeapSupplements.
230 class GC_PLUGIN_IGNORE("http://crbug.com/395036") PersistentHeapSupplementable : public SupplementableBase<T, true> {
232 PersistentHeapSupplementable() : m_root(this) { }
233 virtual ~PersistentHeapSupplementable()
235 typedef typename SupplementableTraits<T, true>::SupplementMap::iterator SupplementIterator;
236 for (SupplementIterator it = this->m_supplements.begin(); it != this->m_supplements.end(); ++it)
237 it->value->persistentHostHasBeenDestroyed();
240 virtual void trace(Visitor* visitor)
242 visitor->trace(this->m_supplements);
243 SupplementableBase<T, true>::trace(visitor);
247 class TraceDelegate : PersistentBase<ThreadLocalPersistents<AnyThread>, TraceDelegate> {
249 TraceDelegate(PersistentHeapSupplementable* owner) : m_owner(owner) { }
250 void trace(Visitor* visitor) { m_owner->trace(visitor); }
252 PersistentHeapSupplementable* m_owner;
255 TraceDelegate m_root;
259 class Supplement : public SupplementBase<T, false> { };
261 // This class is used to make an off-heap class supplementable with off-heap
262 // supplements (Supplement).
264 class GC_PLUGIN_IGNORE("http://crbug.com/395036") Supplementable : public SupplementableBase<T, false> {
266 virtual void trace(Visitor* visitor)
268 // No tracing of off-heap supplements. We should not have any Supplementable
269 // object on the heap. Either the object is HeapSupplementable or if it is
270 // off heap it should use PersistentHeapSupplementable to trace any on-heap
272 COMPILE_ASSERT(!IsGarbageCollectedType<T>::value, GarbageCollectedObjectMustBeHeapSupplementable);
273 SupplementableBase<T, false>::trace(visitor);
278 struct ThreadingTrait<SupplementBase<T, true> > {
279 static const ThreadAffinity Affinity = ThreadingTrait<T>::Affinity;
283 struct ThreadingTrait<SupplementableBase<T, true> > {
284 static const ThreadAffinity Affinity = ThreadingTrait<T>::Affinity;
289 #endif // Supplementable_h