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 {
  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()
  53         : m_refCount(1)
  54 #ifndef NDEBUG
  55         , m_deletionHasBegun(false)
  56 #endif
  57     {
  58     }
  59
  60     ~RefCountedBase()
  61     {
  62     }
  63
  64     // Returns whether the pointer should be freed or not.
  65     bool derefBase()
  66     {
  67         ASSERT(!m_deletionHasBegun);
  68         ASSERT(m_refCount > 0);
  69         if (m_refCount == 1) {
  70 #ifndef NDEBUG
  71             m_deletionHasBegun = true;
  72 #endif
  73             return true;
  74         }
  75
  76         --m_refCount;
  77         return false;
  78     }
  79
  80     // Helper for generating JIT code. Please do not use for non-JIT purposes.
  81     int* addressOfCount()
  82     {
  83         return &m_refCount;
  84     }
  85
  86 #ifndef NDEBUG
  87     bool deletionHasBegun() const
  88     {
  89         return m_deletionHasBegun;
  90     }
  91 #endif
  92
  93 private:
  94     template<class T>
  95     friend class CrossThreadRefCounted;
  96
  97     int m_refCount;
  98 #ifndef NDEBUG
  99     bool m_deletionHasBegun;
 100 #endif
 101 };
 102
 103
 104 template<class T> class RefCounted : public RefCountedBase, public Noncopyable {
 105 public:
 106     void deref()
 107     {
 108         if (derefBase())
 109             delete static_cast<T*>(this);
 110     }
 111
 112 protected:
 113     ~RefCounted()
 114     {
 115     }
 116 };
 117
 118 template<class T> class RefCountedCustomAllocated : public RefCountedBase, public NoncopyableCustomAllocated {
 119 public:
 120     void deref()
 121     {
 122         if (derefBase())
 123             delete static_cast<T*>(this);
 124     }
 125
 126 protected:
 127     ~RefCountedCustomAllocated()
 128     {
 129     }
 130 };
 131
 132 } // namespace WTF
 133
 134 using WTF::RefCounted;
 135 using WTF::RefCountedCustomAllocated;
 136
 137 #endif // RefCounted_h