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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;
106 struct SupplementableTraits<T, false> {
107 typedef PassOwnPtr<SupplementBase<T, false> > SupplementArgumentType;
111 class SupplementTracing;
114 class SupplementTracing<true> : public GarbageCollectedMixin { };
117 class SupplementTracing<false> {
119 virtual ~SupplementTracing() { }
120 // FIXME: Oilpan: this trace() method is only provided to minimize
121 // the use of ENABLE(OILPAN) for Supplements deriving from the
122 // transition type WillBeHeapSupplement<>.
124 // When that transition type is removed (or its use is substantially
125 // reduced), remove this dummy trace method also.
126 virtual void trace(Visitor*) { }
129 template<typename T, bool isGarbageCollected = false>
130 class SupplementBase : public SupplementTracing<isGarbageCollected> {
132 #if ENABLE(SECURITY_ASSERT)
133 virtual bool isRefCountedWrapper() const { return false; }
136 static void provideTo(SupplementableBase<T, isGarbageCollected>& host, const char* key, typename SupplementableTraits<T, isGarbageCollected>::SupplementArgumentType supplement)
138 host.provideSupplement(key, supplement);
141 static SupplementBase<T, isGarbageCollected>* from(SupplementableBase<T, isGarbageCollected>& host, const char* key)
143 return host.requireSupplement(key);
146 static SupplementBase<T, isGarbageCollected>* from(SupplementableBase<T, isGarbageCollected>* host, const char* key)
148 return host ? host->requireSupplement(key) : 0;
152 template<typename T, bool isGarbageCollected>
153 class SupplementableTracing;
156 class SupplementableTracing<T, true> : public GarbageCollectedMixin {
158 virtual void trace(Visitor* visitor)
160 visitor->trace(m_supplements);
164 typedef HeapHashMap<const char*, Member<SupplementBase<T, true> >, PtrHash<const char*> > SupplementMap;
165 SupplementMap m_supplements;
169 class SupplementableTracing<T, false> {
171 typedef HashMap<const char*, OwnPtr<SupplementBase<T, false> >, PtrHash<const char*> > SupplementMap;
172 SupplementMap m_supplements;
175 // Helper class for implementing Supplementable and HeapSupplementable.
176 template<typename T, bool isGarbageCollected = false>
177 class SupplementableBase : public SupplementableTracing<T, isGarbageCollected> {
179 void provideSupplement(const char* key, typename SupplementableTraits<T, isGarbageCollected>::SupplementArgumentType supplement)
181 ASSERT(m_threadId == currentThread());
182 ASSERT(!this->m_supplements.get(key));
183 this->m_supplements.set(key, supplement);
186 void removeSupplement(const char* key)
188 ASSERT(m_threadId == currentThread());
189 this->m_supplements.remove(key);
192 SupplementBase<T, isGarbageCollected>* requireSupplement(const char* key)
194 ASSERT(m_threadId == currentThread());
195 return this->m_supplements.get(key);
198 void reattachThread()
201 m_threadId = currentThread();
207 SupplementableBase() : m_threadId(currentThread()) { }
210 ThreadIdentifier m_threadId;
215 class HeapSupplement : public SupplementBase<T, true> { };
218 class HeapSupplementable : public SupplementableBase<T, true> { };
221 class Supplement : public SupplementBase<T, false> { };
224 class Supplementable : public SupplementableBase<T, false> { };
227 struct ThreadingTrait<SupplementBase<T, true> > {
228 static const ThreadAffinity Affinity = ThreadingTrait<T>::Affinity;
232 struct ThreadingTrait<SupplementableBase<T, true> > {
233 static const ThreadAffinity Affinity = ThreadingTrait<T>::Affinity;
238 #endif // Supplementable_h