wtf/RefCounted.h

   1 /*
   2  * Copyright (C) 2006, 2007, 2008, 2009, 2010 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 "Assertions.h"
  25 #include "FastAllocBase.h"
  26 #include "Noncopyable.h"
  27
  28 namespace WTF {
  29
  30 // This base class holds the non-template methods and attributes.
  31 // The RefCounted class inherits from it reducing the template bloat
  32 // generated by the compiler (technique called template hoisting).
  33 class RefCountedBase {
  34 public:
  35     void ref()
  36     {
  37         ASSERT(!m_deletionHasBegun);
  38         ASSERT(!m_adoptionIsRequired);
  39         ++m_refCount;
  40     }
  41
  42     bool hasOneRef() const
  43     {
  44         ASSERT(!m_deletionHasBegun);
  45         return m_refCount == 1;
  46     }
  47
  48     int refCount() const
  49     {
  50         return m_refCount;
  51     }
  52
  53     void relaxAdoptionRequirement()
  54     {
  55 #ifndef NDEBUG
  56         ASSERT(!m_deletionHasBegun);
  57         ASSERT(m_adoptionIsRequired);
  58         m_adoptionIsRequired = false;
  59 #endif
  60     }
  61
  62     // Helper for generating JIT code. Please do not use for non-JIT purposes.
  63     const int* addressOfCount() const
  64     {
  65         return &m_refCount;
  66     }
  67
  68 protected:
  69     RefCountedBase()
  70         : m_refCount(1)
  71 #ifndef NDEBUG
  72         , m_deletionHasBegun(false)
  73         , m_adoptionIsRequired(true)
  74 #endif
  75     {
  76     }
  77
  78     ~RefCountedBase()
  79     {
  80         ASSERT(m_deletionHasBegun);
  81         ASSERT(!m_adoptionIsRequired);
  82     }
  83
  84     // Returns whether the pointer should be freed or not.
  85     bool derefBase()
  86     {
  87         ASSERT(!m_deletionHasBegun);
  88         ASSERT(!m_adoptionIsRequired);
  89
  90         ASSERT(m_refCount > 0);
  91         if (m_refCount == 1) {
  92 #ifndef NDEBUG
  93             m_deletionHasBegun = true;
  94 #endif
  95             return true;
  96         }
  97
  98         --m_refCount;
  99         return false;
 100     }
 101
 102 #ifndef NDEBUG
 103     bool deletionHasBegun() const
 104     {
 105         return m_deletionHasBegun;
 106     }
 107 #endif
 108
 109 private:
 110     template<typename T> friend class CrossThreadRefCounted;
 111
 112 #ifndef NDEBUG
 113     friend void adopted(RefCountedBase*);
 114 #endif
 115
 116     int m_refCount;
 117 #ifndef NDEBUG
 118     bool m_deletionHasBegun;
 119     bool m_adoptionIsRequired;
 120 #endif
 121 };
 122
 123 #ifndef NDEBUG
 124
 125 inline void adopted(RefCountedBase* object)
 126 {
 127     if (!object)
 128         return;
 129     ASSERT(!object->m_deletionHasBegun);
 130     object->m_adoptionIsRequired = false;
 131 }
 132
 133 #endif
 134
 135 template<typename T> class RefCounted : public RefCountedBase {
 136     WTF_MAKE_NONCOPYABLE(RefCounted); WTF_MAKE_FAST_ALLOCATED;
 137 public:
 138     void deref()
 139     {
 140         if (derefBase())
 141             delete static_cast<T*>(this);
 142     }
 143
 144 protected:
 145     RefCounted() { }
 146     ~RefCounted()
 147     {
 148     }
 149 };
 150
 151 template<typename T> class RefCountedCustomAllocated : public RefCountedBase {
 152     WTF_MAKE_NONCOPYABLE(RefCountedCustomAllocated);
 153
 154 public:
 155     void deref()
 156     {
 157         if (derefBase())
 158             delete static_cast<T*>(this);
 159     }
 160
 161 protected:
 162     ~RefCountedCustomAllocated()
 163     {
 164     }
 165 };
 166
 167 } // namespace WTF
 168
 169 using WTF::RefCounted;
 170 using WTF::RefCountedCustomAllocated;
 171
 172 #endif // RefCounted_h