--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/WebCore/platform/TreeShared.h	Fri Sep 17 09:02:29 2010 +0300
@@ -0,0 +1,146 @@
+/*
+ * Copyright (C) 2006, 2007, 2009, 2010 Apple Inc. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public License
+ * along with this library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ *
+ */
+
+#ifndef TreeShared_h
+#define TreeShared_h
+
+#include <wtf/Assertions.h>
+#include <wtf/Noncopyable.h>
+#include <wtf/Threading.h>
+
+namespace WebCore {
+
+#ifndef NDEBUG
+template<typename T> class TreeShared;
+template<typename T> void adopted(TreeShared<T>*);
+#endif
+
+template<typename T> class TreeShared : public Noncopyable {
+public:
+    TreeShared(int initialRefCount = 1)
+        : m_refCount(initialRefCount)
+        , m_parent(0)
+#ifndef NDEBUG
+        , m_adoptionIsRequired(initialRefCount == 1)
+#endif
+    {
+        ASSERT(isMainThread());
+#ifndef NDEBUG
+        m_deletionHasBegun = false;
+        m_inRemovedLastRefFunction = false;
+#endif
+    }
+    virtual ~TreeShared()
+    {
+        ASSERT(isMainThread());
+        ASSERT(!m_refCount);
+        ASSERT(m_deletionHasBegun);
+        ASSERT(!m_adoptionIsRequired);
+    }
+
+    void ref()
+    {
+        ASSERT(isMainThread());
+        ASSERT(!m_deletionHasBegun);
+        ASSERT(!m_inRemovedLastRefFunction);
+        ASSERT(!m_adoptionIsRequired);
+        ++m_refCount;
+    }
+
+    void deref()
+    {
+        ASSERT(isMainThread());
+        ASSERT(m_refCount >= 0);
+        ASSERT(!m_deletionHasBegun);
+        ASSERT(!m_inRemovedLastRefFunction);
+        ASSERT(!m_adoptionIsRequired);
+        if (--m_refCount <= 0 && !m_parent) {
+#ifndef NDEBUG
+            m_inRemovedLastRefFunction = true;
+#endif
+            removedLastRef();
+        }
+    }
+
+    bool hasOneRef() const
+    {
+        ASSERT(!m_deletionHasBegun);
+        ASSERT(!m_inRemovedLastRefFunction);
+        return m_refCount == 1;
+    }
+
+    int refCount() const
+    {
+        return m_refCount;
+    }
+
+    void setParent(T* parent)
+    { 
+        ASSERT(isMainThread());
+        m_parent = parent; 
+    }
+
+    T* parent() const
+    {
+        ASSERT(isMainThread());
+        return m_parent;
+    }
+
+#ifndef NDEBUG
+    bool m_deletionHasBegun;
+    bool m_inRemovedLastRefFunction;
+#endif
+
+private:
+#ifndef NDEBUG
+    friend void adopted<>(TreeShared<T>*);
+#endif
+
+    virtual void removedLastRef()
+    {
+#ifndef NDEBUG
+        m_deletionHasBegun = true;
+#endif
+        delete this;
+    }
+
+    int m_refCount;
+    T* m_parent;
+#ifndef NDEBUG
+    bool m_adoptionIsRequired;
+#endif
+};
+
+#ifndef NDEBUG
+
+template<typename T> inline void adopted(TreeShared<T>* object)
+{
+    if (!object)
+        return;
+    ASSERT(!object->m_deletionHasBegun);
+    ASSERT(!object->m_inRemovedLastRefFunction);
+    object->m_adoptionIsRequired = false;
+}
+
+#endif
+
+}
+
+#endif // TreeShared.h