blocxx
COWIntrusiveCountableBase.hpp
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38//
39// Copyright (c) 2001, 2002 Peter Dimov
40//
41// Permission to copy, use, modify, sell and distribute this software
42// is granted provided this copyright notice appears in all copies.
43// This software is provided "as is" without express or implied
44// warranty, and with no claim as to its suitability for any purpose.
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46
47#ifndef BLOCXX_COW_INTRUSIVE_COUNTABLE_BASE_HPP_INCLUDE_GUARD_
48#define BLOCXX_COW_INTRUSIVE_COUNTABLE_BASE_HPP_INCLUDE_GUARD_
49
50#include "blocxx/BLOCXX_config.h"
51#include "blocxx/RefCount.hpp"
52
53namespace BLOCXX_NAMESPACE
54{
55
71
76template <typename T> T* COWIntrusiveReferenceClone(T* p);
77
78class BLOCXX_COMMON_API COWIntrusiveCountableBase
79{
80private:
82
83protected:
90
97 {
98 // don't assign or change the ref count, since it won't be different.
99 return *this;
100 }
101
108
113
118 {
119 return m_usecount;
120 }
121
122public:
129 {
130 p->m_usecount.inc();
131 }
132
141 {
142 if (p->m_usecount.decAndTest())
143 delete p;
144 }
145
153 {
154 return p->m_usecount.get() == 1;
155 }
156
162 template <typename T>
163 friend T* COWIntrusiveReferenceClone(T* p);
164};
165
166template <typename T>
168{
169 // this needs to happen first to avoid a race condition between
170 // another thread deleting the object and this one making a copy.
171 T* tmp = p->clone();
172 if (p->m_usecount.decAndTest())
173 {
174 // only copy--don't need to clone, also not a race condition.
175 // undo the decAndTest.
176 p->m_usecount.inc();
177 delete tmp; // we won't need this anymore.
178 return p;
179 }
180 else
181 {
182 // need to become unique
183 if (tmp)
185
186 return tmp;
187 }
188}
189
190} // end namespace BLOCXX_NAMESPACE
191
192#endif
193
194
COWIntrusiveCountableBase(COWIntrusiveCountableBase const &)
Copy constructor.
friend void COWIntrusiveReferenceRelease(COWIntrusiveCountableBase *p)
Release a reference on a COWIntrusiveCountableBase.
COWIntrusiveCountableBase & operator=(COWIntrusiveCountableBase const &x)
Assignment operator.
friend void COWIntrusiveReferenceAddRef(COWIntrusiveCountableBase *p)
Increment the reference count for a COWIntrusiveCountableBase object.
friend bool COWIntrusiveReferenceUnique(COWIntrusiveCountableBase *p)
Determine of a COWIntrusiveCountableBase only has one reference.
Taken from RFC 1321.
void COWIntrusiveReferenceAddRef(COWIntrusiveCountableBase *p)
void COWIntrusiveReferenceRelease(COWIntrusiveCountableBase *p)
bool COWIntrusiveReferenceUnique(COWIntrusiveCountableBase *p)