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1 /*
2  *  Copyright (C) 2005, 2006, 2008 Apple Inc. All rights reserved.
3  *
4  *  This library is free software; you can redistribute it and/or
5  *  modify it under the terms of the GNU Library General Public
6  *  License as published by the Free Software Foundation; either
7  *  version 2 of the License, or (at your option) any later version.
8  *
9  *  This library is distributed in the hope that it will be useful,
10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12  *  Library General Public License for more details.
13  *
14  *  You should have received a copy of the GNU Library General Public License
15  *  along with this library; see the file COPYING.LIB.  If not, write to
16  *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
17  *  Boston, MA 02110-1301, USA.
18  *
19  */
20 
21 #ifndef WTF_ListRefPtr_h
22 #define WTF_ListRefPtr_h
23 
24 #include <wtf/RefPtr.h>
25 
26 namespace WTF {
27 
28     // Specialized version of RefPtr desgined for use in singly-linked lists.
29     // Derefs the list iteratively to avoid recursive derefing that can overflow the stack.
30     template <typename T> class ListRefPtr : public RefPtr<T> {
31     public:
ListRefPtr()32         ListRefPtr() : RefPtr<T>() {}
ListRefPtr(T * ptr)33         ListRefPtr(T* ptr) : RefPtr<T>(ptr) {}
ListRefPtr(const RefPtr<T> & o)34         ListRefPtr(const RefPtr<T>& o) : RefPtr<T>(o) {}
35         // see comment in PassRefPtr.h for why this takes const reference
ListRefPtr(const PassRefPtr<U> & o)36         template <typename U> ListRefPtr(const PassRefPtr<U>& o) : RefPtr<T>(o) {}
37 
~ListRefPtr()38         ~ListRefPtr()
39         {
40             RefPtr<T> reaper = this->release();
41             while (reaper && reaper->hasOneRef())
42                 reaper = reaper->releaseNext(); // implicitly protects reaper->next, then derefs reaper
43         }
44 
45         ListRefPtr& operator=(T* optr) { RefPtr<T>::operator=(optr); return *this; }
46         ListRefPtr& operator=(const RefPtr<T>& o) { RefPtr<T>::operator=(o); return *this; }
47         ListRefPtr& operator=(const PassRefPtr<T>& o) { RefPtr<T>::operator=(o); return *this; }
48         template <typename U> ListRefPtr& operator=(const RefPtr<U>& o) { RefPtr<T>::operator=(o); return *this; }
49         template <typename U> ListRefPtr& operator=(const PassRefPtr<U>& o) { RefPtr<T>::operator=(o); return *this; }
50     };
51 
getPtr(const ListRefPtr<T> & p)52     template <typename T> inline T* getPtr(const ListRefPtr<T>& p)
53     {
54         return p.get();
55     }
56 
57 } // namespace WTF
58 
59 using WTF::ListRefPtr;
60 
61 #endif // WTF_ListRefPtr_h
62