WebCore/TreeShared.h

   1 /*
   2  * Copyright (C) 2006, 2007 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 <wtf/Assertions.h>
  25 #include <wtf/Noncopyable.h>
  26
  27 namespace WebCore {
  28
  29 template<class T> class TreeShared : Noncopyable {
  30 public:
  31     TreeShared()
  32         : m_refCount(0)
  33         , m_parent(0)
  34     {
  35 #ifndef NDEBUG
  36         m_deletionHasBegun = false;
  37         m_inRemovedLastRefFunction = false;
  38 #endif
  39     }
  40     TreeShared(T* parent)
  41         : m_refCount(0)
  42         , m_parent(0)
  43     {
  44 #ifndef NDEBUG
  45         m_deletionHasBegun = false;
  46         m_inRemovedLastRefFunction = false;
  47 #endif
  48     }
  49     virtual ~TreeShared()
  50     {
  51         ASSERT(m_deletionHasBegun);
  52     }
  53
  54     void ref()
  55     {
  56         ASSERT(!m_deletionHasBegun);
  57         ASSERT(!m_inRemovedLastRefFunction);
  58         ++m_refCount;
  59     }
  60
  61     void deref()
  62     {
  63         ASSERT(!m_deletionHasBegun);
  64         ASSERT(!m_inRemovedLastRefFunction);
  65         if (--m_refCount <= 0 && !m_parent) {
  66 #ifndef NDEBUG
  67             m_inRemovedLastRefFunction = true;
  68 #endif
  69             removedLastRef();
  70         }
  71     }
  72
  73     bool hasOneRef() const
  74     {
  75         ASSERT(!m_deletionHasBegun);
  76         ASSERT(!m_inRemovedLastRefFunction);
  77         return m_refCount == 1;
  78     }
  79
  80     int refCount() const
  81     {
  82         return m_refCount;
  83     }
  84
  85     void setParent(T* parent) { m_parent = parent; }
  86     T* parent() const { return m_parent; }
  87
  88 #ifndef NDEBUG
  89     bool m_deletionHasBegun;
  90     bool m_inRemovedLastRefFunction;
  91 #endif
  92
  93 private:
  94     virtual void removedLastRef()
  95     {
  96 #ifndef NDEBUG
  97         m_deletionHasBegun = true;
  98 #endif
  99         delete this;
 100     }
 101
 102     int m_refCount;
 103     T* m_parent;
 104 };
 105
 106 }
 107
 108 #endif // TreeShared.h