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      1 /*
      2  * Copyright (C) 2009 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 OwnHandle_h
     32 #define OwnHandle_h
     33 
     34 #include <v8.h>
     35 
     36 namespace WebCore {
     37 
     38     template<typename T>
     39     class OwnHandle {
     40     public:
     41         OwnHandle() { }
     42         explicit OwnHandle(v8::Handle<T> handle) : m_handle(v8::Persistent<T>::New(handle)) { }
     43         ~OwnHandle() { clear(); }
     44 
     45         v8::Handle<T> get() const { return m_handle; }
     46         void set(v8::Handle<T> handle) { clear(); m_handle = v8::Persistent<T>::New(handle); }
     47 
     48         // Note: This is clear in the OwnPtr sense, not the v8::Handle sense.
     49         void clear()
     50         {
     51             if (m_handle.IsEmpty())
     52                 return;
     53             if (m_handle.IsWeak())
     54                 m_handle.ClearWeak();
     55             m_handle.Dispose();
     56             m_handle.Clear();
     57         }
     58 
     59         // Make the underlying handle weak.  The client doesn't get a callback,
     60         // we just make the handle empty.
     61         void makeWeak()
     62         {
     63             if (m_handle.IsEmpty())
     64                 return;
     65             m_handle.MakeWeak(this, &OwnHandle<T>::weakCallback);
     66         }
     67 
     68     private:
     69         static void weakCallback(v8::Persistent<v8::Value> object, void* ownHandle)
     70         {
     71             OwnHandle<T>* handle = static_cast<OwnHandle<T>*>(ownHandle);
     72             handle->clear();
     73         }
     74 
     75         v8::Persistent<T> m_handle;
     76     };
     77 
     78 } // namespace WebCore
     79 
     80 #endif // OwnHandle_h
     81