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      1 /*
      2  * Copyright (C) 2006, 2007, 2009, 2010, 2012 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 TreeShared_h
     22 #define TreeShared_h
     23 
     24 #include "public/platform/WebPrivatePtr.h"
     25 #include "wtf/Assertions.h"
     26 #include "wtf/MainThread.h"
     27 #include "wtf/Noncopyable.h"
     28 
     29 namespace blink {
     30 
     31 #if ENABLE(SECURITY_ASSERT)
     32 template<typename NodeType> class TreeShared;
     33 template<typename NodeType> void adopted(TreeShared<NodeType>*);
     34 #endif
     35 
     36 template<typename NodeType> class TreeShared : public NoBaseWillBeGarbageCollectedFinalized<NodeType> {
     37     WTF_MAKE_NONCOPYABLE(TreeShared);
     38 protected:
     39     TreeShared()
     40         : m_refCount(1)
     41 #if ENABLE(SECURITY_ASSERT)
     42         , m_deletionHasBegun(false)
     43 #if ENABLE(ASSERT)
     44         , m_inRemovedLastRefFunction(false)
     45         , m_adoptionIsRequired(true)
     46 #endif
     47 #endif
     48     {
     49         ASSERT(isMainThread());
     50     }
     51 
     52     ~TreeShared()
     53     {
     54         ASSERT(isMainThread());
     55         ASSERT(!m_refCount);
     56         ASSERT_WITH_SECURITY_IMPLICATION(m_deletionHasBegun);
     57         ASSERT(!m_adoptionIsRequired);
     58     }
     59 
     60 public:
     61     void ref()
     62     {
     63         ASSERT(isMainThread());
     64         ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun);
     65         ASSERT(!m_inRemovedLastRefFunction);
     66         ASSERT(!m_adoptionIsRequired);
     67         ++m_refCount;
     68     }
     69 
     70     void deref()
     71     {
     72         ASSERT(isMainThread());
     73         ASSERT(m_refCount > 0);
     74         ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun);
     75         ASSERT(!m_inRemovedLastRefFunction);
     76         ASSERT(!m_adoptionIsRequired);
     77         NodeType* thisNode = static_cast<NodeType*>(this);
     78         if (!--m_refCount && !thisNode->hasTreeSharedParent()) {
     79 #if ENABLE(ASSERT)
     80             m_inRemovedLastRefFunction = true;
     81 #endif
     82             thisNode->removedLastRef();
     83         }
     84     }
     85 
     86     int refCount() const { return m_refCount; }
     87 
     88 private:
     89     int m_refCount;
     90 
     91 #if ENABLE(SECURITY_ASSERT)
     92 public:
     93     bool m_deletionHasBegun;
     94 #if ENABLE(ASSERT)
     95     bool m_inRemovedLastRefFunction;
     96 
     97 private:
     98     friend void adopted<>(TreeShared<NodeType>*);
     99     bool m_adoptionIsRequired;
    100 #endif
    101 #endif
    102 };
    103 
    104 #if ENABLE(SECURITY_ASSERT)
    105 template<typename NodeType> void adopted(TreeShared<NodeType>* object)
    106 {
    107     if (!object)
    108         return;
    109 
    110     ASSERT_WITH_SECURITY_IMPLICATION(!object->m_deletionHasBegun);
    111 #if ENABLE(ASSERT)
    112     ASSERT(!object->m_inRemovedLastRefFunction);
    113     object->m_adoptionIsRequired = false;
    114 #endif
    115 }
    116 #endif
    117 
    118 }
    119 
    120 #endif // TreeShared.h
    121