wtf/RefCounted.h

   1 /*
   2  * Copyright (C) 2006, 2007, 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 RefCounted_h
  22 #define RefCounted_h
  23
  24 #include <wtf/Assertions.h>
  25 #include <wtf/Noncopyable.h>
  26
  27 namespace WTF {
  28
  29 // This base class holds the non-template methods and attributes.
  30 // The RefCounted class inherits from it reducing the template bloat
  31 // generated by the compiler (technique called template hoisting).
  32 class RefCountedBase : Noncopyable {
  33 public:
  34     void ref()
  35     {
  36         ASSERT(!m_deletionHasBegun);
  37         ++m_refCount;
  38     }
  39
  40     bool hasOneRef() const
  41     {
  42         ASSERT(!m_deletionHasBegun);
  43         return m_refCount == 1;
  44     }
  45
  46     int refCount() const
  47     {
  48         return m_refCount;
  49     }
  50
  51 protected:
  52     RefCountedBase(int initialRefCount)
  53         : m_refCount(initialRefCount)
  54 #ifndef NDEBUG
  55         , m_deletionHasBegun(false)
  56 #endif
  57     {
  58     }
  59
  60     ~RefCountedBase() {}
  61
  62     // Returns whether the pointer should be freed or not.
  63     bool derefBase()
  64     {
  65         ASSERT(!m_deletionHasBegun);
  66         ASSERT(m_refCount > 0);
  67         if (m_refCount == 1) {
  68 #ifndef NDEBUG
  69             m_deletionHasBegun = true;
  70 #endif
  71             return true;
  72         }
  73
  74         --m_refCount;
  75         return false;
  76     }
  77
  78 protected:
  79     int m_refCount;
  80 #ifndef NDEBUG
  81     bool m_deletionHasBegun;
  82 #endif
  83 };
  84
  85
  86 template<class T> class RefCounted : public RefCountedBase {
  87 public:
  88     RefCounted(int initialRefCount = 1)
  89         : RefCountedBase(initialRefCount)
  90     {
  91     }
  92
  93     void deref()
  94     {
  95         if (derefBase())
  96             delete static_cast<T*>(this);
  97     }
  98
  99 protected:
 100     ~RefCounted() {}
 101 };
 102
 103 } // namespace WTF
 104
 105 using WTF::RefCounted;
 106
 107 #endif // RefCounted_h