singleton.h
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1 /*
2  * Copyright (C) 2005-2006 by Marc Boris Duerner
3  * Copyright (C) 2006 by Aloysius Indrayanto
4  *
5  * This library is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU Lesser General Public
7  * License as published by the Free Software Foundation; either
8  * version 2.1 of the License, or (at your option) any later version.
9  *
10  * As a special exception, you may use this file as part of a free
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12  * instantiate templates or use macros or inline functions from this
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15  * resulting executable to be covered by the GNU General Public
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18  * General Public License.
19  *
20  * This library is distributed in the hope that it will be useful,
21  * but WITHOUT ANY WARRANTY; without even the implied warranty of
22  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23  * Lesser General Public License for more details.
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28  */
29 #ifndef cxxtools_Singleton_h
30 #define cxxtools_Singleton_h
31 
32 #include <cxxtools/noncopyable.h>
33 
34 #include <memory>
35 #include <cstdlib>
36 
37 namespace cxxtools {
38 
60  template <typename T, typename A = std::allocator<T> >
61  class Singleton : private NonCopyable
62  {
63  public:
64  typedef A Allocator;
65 
66  public:
75  static T& instance()
76  {
77  if(!_instance)
78  {
79  try
80  {
81  _instance = (T*)_allocator.allocate(1);
82  new (_instance) T();
83  std::atexit(&atExit);
84  }
85  catch( const std::bad_alloc& e )
86  {
87  throw e;
88  }
89  catch(...)
90  {
91  _allocator.deallocate(_instance, 1);
92  _instance = 0;
93  throw;
94  }
95  }
96 
97  return *_instance;
98  }
99 
100  protected:
104  { }
105 
109  { }
110 
111  private:
118  static void atExit()
119  {
120  _instance->~T();
121  _allocator.deallocate(_instance, 1);
122  _instance = 0;
123  }
124 
125  private:
126  static A _allocator;
127  static T* _instance;
128  };
129 
130 
131  template <typename T, typename A>
132  A Singleton<T, A>::_allocator;
133 
134 
135  template <typename T, typename A>
136  T* Singleton<T, A>::_instance = 0;
137 
138 } // namespace cxxtools
139 
140 #endif