extl/utility/_old_singleton.h

   1 /* ///////////////////////////////////////////////////////////////////////
   2  * File:                singleton.h
   3  *
   4  * Created:             08.04.17
   5  * Updated:             08.04.17
   6  *
   7  * Brief: Create an instance only before main() begins
   8  *
   9  * [<Home>]
  10  * Copyright (c) 2008-2020, Waruqi All rights reserved.
  11  * //////////////////////////////////////////////////////////////////// */
  12
  13 #ifndef EXTL_UTILITY_SINGLETON_H
  14 #define EXTL_UTILITY_SINGLETON_H
  15
  16 /*!\file singleton.h
  17  * \brief Create an instance only before main() begins
  18  */
  19 #ifndef __cplusplus
  20 #       error singleton.h need be supported by c++.
  21 #endif
  22
  23 /* ///////////////////////////////////////////////////////////////////////
  24  * Includes
  25  */
  26 #include "../prefix.h"
  27 #include "../synch/synch_traits_selector.h"
  28 #include "../synch/scoped_lock.h"
  29 /* ///////////////////////////////////////////////////////////////////////
  30  * ::extl namespace
  31  */
  32 EXTL_BEGIN_NAMESPACE
  33
  34 /*!\brief singleton class
  35  *
  36  * \param T The object type
  37  *
  38  * \ingroup extl_group_synch
  39  */
  40 template< typename_param_k T >
  41 class singleton
  42 {
  43         public:
  44                 typedef singleton<T>                                    class_type;
  45                 typedef T                                                               object_type;
  46
  47         private:
  48                 static class_type                                               s_self;
  49                 static object_type*                                             s_object;
  50
  51         private:
  52                 void do_nothing() const {}
  53
  54         public:
  55                 /* Ensure the instance() is called before main() begins */
  56                 singleton()
  57                 {
  58                         object_type& obj = class_type::instance();
  59                 }
  60                 ~singleton()
  61                 {
  62                         uninit();
  63                 }
  64                 /* Initializes the object and allows multiple initialization */
  65                 static void init()
  66                 {
  67                         if(NULL == object())
  68                         {
  69                                 object() = new object_type();
  70                         }
  71                 }
  72
  73                 /* Uninitializes the object */
  74                 static void uninit()
  75                 {
  76                         if(NULL != object())
  77                         {
  78                                 delete object();
  79                                 object() = NULL;
  80                         }
  81                 }
  82
  83                 /* Returns the pointer reference to static object */
  84                 static object_type*& object()
  85                 {
  86                 #ifdef EXTL_COMPILER_IS_DMC
  87                         static object_type* p = NULL;
  88                         return p;
  89                 #else /* DMC: Link error */
  90                         return s_object;
  91                 #endif
  92                 }
  93
  94         public:
  95                 /* Returns a reference of the object */
  96                 static object_type& instance()
  97                 {
  98                         /* Initializes the object and allows multiple initialization */
  99                         init();
 100
 101                         /* Force the instantiation of singleton<T>,
 102                          * whose constructor is called before main() begins
 103                          */
 104                         s_self.do_nothing();
 105
 106                         EXTL_MESSAGE_ASSERT(NULL != object(), "The singleton is not existed!");
 107                         return *object();
 108                 }
 109 };
 110 template < typename_param_k T >
 111 typename_type_k singleton<T>::object_type* singleton<T>::s_object = NULL;
 112
 113 template < typename_param_k T >
 114 singleton<T> singleton<T>::s_self;
 115
 116 /* ///////////////////////////////////////////////////////////////////////
 117  * ::extl namespace
 118  */
 119 EXTL_END_NAMESPACE
 120
 121 /* //////////////////////////////////////////////////////////////////// */
 122 #endif /* EXTL_UTILITY_SINGLETON_H */
 123 /* //////////////////////////////////////////////////////////////////// */