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      1 /*
      2  * Copyright (C) 2014 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
     13  * distribution.
     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #ifndef V8GarbageCollected_h
     32 #define V8GarbageCollected_h
     33 
     34 #include <v8.h>
     35 
     36 namespace WebCore {
     37 
     38 template<typename T>
     39 class V8GarbageCollected {
     40     WTF_MAKE_NONCOPYABLE(V8GarbageCollected);
     41 public:
     42     static T* Cast(v8::Handle<v8::Value> value)
     43     {
     44         ASSERT(value->IsExternal());
     45         T* result = static_cast<T*>(value.As<v8::External>()->Value());
     46         RELEASE_ASSERT(result->m_handle == value);
     47         return result;
     48     }
     49 
     50 protected:
     51     V8GarbageCollected(v8::Isolate* isolate)
     52         : m_isolate(isolate)
     53         , m_handle(isolate, v8::External::New(isolate, static_cast<T*>(this)))
     54         , m_releasedToV8GarbageCollector(false)
     55     {
     56     }
     57 
     58     v8::Handle<v8::External> releaseToV8GarbageCollector()
     59     {
     60         ASSERT(!m_handle.isWeak()); // Call this exactly once.
     61         m_releasedToV8GarbageCollector = true;
     62         v8::Handle<v8::External> result = m_handle.newLocal(m_isolate);
     63         m_handle.setWeak(static_cast<T*>(this), &weakCallback);
     64         return result;
     65     }
     66 
     67     ~V8GarbageCollected()
     68     {
     69         ASSERT(!m_releasedToV8GarbageCollector || m_handle.isEmpty());
     70     }
     71 
     72     v8::Isolate* isolate() { return m_isolate; }
     73 
     74 private:
     75     static void weakCallback(const v8::WeakCallbackData<v8::External, T>& data)
     76     {
     77         T* self = data.GetParameter();
     78         self->m_handle.clear();
     79         delete self;
     80     }
     81 
     82     v8::Isolate* m_isolate;
     83     ScopedPersistent<v8::External> m_handle;
     84     bool m_releasedToV8GarbageCollector;
     85 };
     86 
     87 } // namespace WebCore
     88 
     89 #endif // V8GarbageCollected_h
     90