blocxx
COWReferenceBase.hpp
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32 
33 
38 #ifndef BLOCXX_CBLOCXX_REFERENCE_BASE_HPP_INCLUDE_GUARD_
39 #define BLOCXX_CBLOCXX_REFERENCE_BASE_HPP_INCLUDE_GUARD_
40 #include "blocxx/BLOCXX_config.h"
41 #include "blocxx/RefCount.hpp"
42 
43 // The classes and functions defined in this file are not meant for general
44 // use, they are internal implementation details. They may change at any time.
45 
46 namespace BLOCXX_NAMESPACE
47 {
48 
50 template<class T>
51 inline void COWRefSwap(T& x, T&y)
52 {
53  T t = x;
54  x = y;
55  y = t;
56 }
57 
59 // This class contains the non-templated code for COWReference, to help
60 // minimize code bloat.
61 class BLOCXX_COMMON_API COWReferenceBase
62 {
63 protected:
64  COWReferenceBase()
65  : m_pRefCount(new RefCount) {}
66  COWReferenceBase(const COWReferenceBase& arg)
67  : m_pRefCount(arg.m_pRefCount)
68  {
69  m_pRefCount->inc();
70  }
71  void incRef()
72  {
73  m_pRefCount->inc();
74  }
75 
76  bool decRef()
77  {
78  if (m_pRefCount->decAndTest())
79  {
80  delete m_pRefCount;
81  return true;
82  }
83  return false;
84  }
85 
86  bool refCountGreaterThanOne() const
87  {
88  return m_pRefCount->get() > 1;
89  }
90 
91  // returns true if we're the only copy.
92  bool getWriteLock()
93  {
94  if (m_pRefCount->decAndTest())
95  {
96  // only copy--don't need to clone, also not a race condition
97  incRef();
98  return true;
99  }
100  else
101  {
102  // need to become unique
103  m_pRefCount = new RefCount;
104  return false;
105  }
106  }
107 
108  void swap(COWReferenceBase& arg)
109  {
110  COWRefSwap(m_pRefCount, arg.m_pRefCount);
111  }
112 
113  void useRefCountOf(const COWReferenceBase& arg)
114  {
115  decRef();
116  m_pRefCount = arg.m_pRefCount;
117  incRef();
118  }
119 
120 protected:
121  RefCount* volatile m_pRefCount;
122 };
123 
124 } // end namespace BLOCXX_NAMESPACE
125 
126 #endif
127 
128 
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