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1 : : /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2 : : /*
3 : : * This file is part of the LibreOffice project.
4 : : *
5 : : * This Source Code Form is subject to the terms of the Mozilla Public
6 : : * License, v. 2.0. If a copy of the MPL was not distributed with this
7 : : * file, You can obtain one at http://mozilla.org/MPL/2.0/.
8 : : *
9 : : * This file incorporates work covered by the following license notice:
10 : : *
11 : : * Licensed to the Apache Software Foundation (ASF) under one or more
12 : : * contributor license agreements. See the NOTICE file distributed
13 : : * with this work for additional information regarding copyright
14 : : * ownership. The ASF licenses this file to you under the Apache
15 : : * License, Version 2.0 (the "License"); you may not use this file
16 : : * except in compliance with the License. You may obtain a copy of
17 : : * the License at http://www.apache.org/licenses/LICENSE-2.0 .
18 : : */
19 : :
20 : : #ifndef _SALHELPER_SINGLETONREF_HXX_
21 : : #define _SALHELPER_SINGLETONREF_HXX_
22 : :
23 : : #include <osl/mutex.hxx>
24 : : #include "rtl/instance.hxx"
25 : : #include "osl/diagnose.h"
26 : : #include "osl/getglobalmutex.hxx"
27 : :
28 : :
29 : : namespace salhelper{
30 : :
31 : :
32 : : /** @short template for implementing singleton classes.
33 : :
34 : : Such classes can be instanciated everytimes they
35 : : are needed. But the internal wrapped object will
36 : : be created one times only. Of course its used
37 : : resources are referenced one times only too.
38 : : This template hold it alive till the last
39 : : reference is gone. Further all operations
40 : : on this reference are threadsafe. Only
41 : : calls directly to the internal object (which modify
42 : : its state) must be made threadsafe by the object itself
43 : : or from outside.
44 : :
45 : : @attention To prevent the code against race conditions, its not
46 : : allowed to start operations inside the ctor
47 : : of the internal wrapped object - especialy operations
48 : : which needs a reference to the same singleton too.
49 : :
50 : : The only chance to supress such strange constellations
51 : : is a lazy-init mechanism.
52 : :
53 : : <ul>
54 : : <li>a) The singleton class can provide a special init()
55 : : method, which must be called as first after creation.</li>
56 : : <li>b) The singleton class can call a special impl_init()
57 : : method implicit for every called interface method.</li>
58 : : </ul>
59 : :
60 : : Note further that this singleton pattern can work only, if
61 : : all user of such singleton are located inside the same library!
62 : : Because static values cant be exported - e.g. from windows libraries.
63 : : */
64 : : template< class SingletonClass >
65 : : class SingletonRef
66 : : {
67 : : //-------------------------------------------
68 : : // member
69 : :
70 : : private :
71 : :
72 : : /** @short pointer to the internal wrapped singleton. */
73 : : static SingletonClass* m_pInstance;
74 : :
75 : : /** @short ref count, which regulate creation and removing of m_pInstance. */
76 : : static sal_Int32 m_nRef;
77 : :
78 : : //-------------------------------------------
79 : : // interface
80 : :
81 : : public :
82 : :
83 : : //---------------------------------------
84 : :
85 : : /** @short standard ctor.
86 : :
87 : : The internal wrapped object is created only,
88 : : if its ref count was 0. Otherwhise this method
89 : : does nothing ... except increasing of the internal
90 : : ref count!
91 : : */
92 : 65893 : SingletonRef()
93 : : {
94 : : // GLOBAL SAFE ->
95 [ + - ][ + - ]: 65893 : ::osl::MutexGuard aLock(SingletonRef::ownStaticLock());
96 : :
97 : : // must be increased before(!) the check is done.
98 : : // Otherwhise this check can fail inside the same thread ...
99 : 65893 : ++m_nRef;
100 [ + + ]: 65893 : if (m_nRef == 1)
101 [ + - ][ + - ]: 656 : m_pInstance = new SingletonClass();
[ # # ]
102 : :
103 [ + - ]: 65893 : OSL_ENSURE(m_nRef>0 && m_pInstance, "Race? Ref count of singleton >0, but instance is NULL!");
104 : : // <- GLOBAL SAFE
105 : 65893 : }
106 : :
107 : : //---------------------------------------
108 : :
109 : : /** @short standard dtor.
110 : :
111 : : The internal wrapped object is removed only,
112 : : if its ref count wil be 0. Otherwhise this method
113 : : does nothing ... except decreasing of the internal
114 : : ref count!
115 : : */
116 : 65854 : ~SingletonRef()
117 : : {
118 : : // GLOBAL SAFE ->
119 [ + - ][ + - ]: 65854 : ::osl::MutexGuard aLock(SingletonRef::ownStaticLock());
120 : :
121 : : // must be decreased before(!) the check is done.
122 : : // Otherwhise this check can fail inside the same thread ...
123 : 65854 : --m_nRef;
124 [ + + ]: 65854 : if (m_nRef == 0)
125 : : {
126 [ + - ][ + - ]: 637 : delete m_pInstance;
127 [ + - ]: 65854 : m_pInstance = 0;
128 : : }
129 : : // <- GLOBAL SAFE
130 : 65854 : }
131 : :
132 : : //---------------------------------------
133 : :
134 : : /** @short Allows rSingle->someBodyOp().
135 : : */
136 : 266754 : SingletonClass* operator->() const
137 : : {
138 : : // GLOBAL SAFE ->
139 [ + - ][ + - ]: 266754 : ::osl::MutexGuard aLock(SingletonRef::ownStaticLock());
140 [ + - ]: 266754 : return m_pInstance;
141 : : // <- GLOBAL SAFE
142 : : }
143 : :
144 : : //---------------------------------------
145 : :
146 : : /** @short Allows (*rSingle).someBodyOp().
147 : : */
148 : 29183 : SingletonClass& operator*() const
149 : : {
150 : : // GLOBAL SAFE ->
151 [ + - ][ + - ]: 29183 : ::osl::MutexGuard aLock(SingletonRef::ownStaticLock());
152 [ + - ]: 29183 : return *m_pInstance;
153 : : // <- GLOBAL SAFE
154 : : }
155 : :
156 : : //-------------------------------------------
157 : : // helper
158 : :
159 : : private :
160 : :
161 : : //---------------------------------------
162 : :
163 : : /** @short creates an own mutex for guarding static contents.
164 : :
165 : : The global mutex the osl library is used one times
166 : : only to create an own static mutex, which can be used
167 : : next time to guard own static member operations.
168 : : */
169 : : struct SingletonLockInit
170 : : {
171 : 530 : ::osl::Mutex* operator()()
172 : : {
173 [ + - ][ + - ]: 530 : static ::osl::Mutex aInstance;
[ + - ][ # # ]
174 : 530 : return &aInstance;
175 : : }
176 : : };
177 : :
178 : 427684 : ::osl::Mutex& ownStaticLock() const
179 : : {
180 : : return *rtl_Instance< ::osl::Mutex,
181 : : SingletonLockInit,
182 : : ::osl::MutexGuard,
183 [ + - ]: 427684 : ::osl::GetGlobalMutex >::create(SingletonLockInit(), ::osl::GetGlobalMutex());
184 : : }
185 : : };
186 : :
187 : : template< class SingletonClass >
188 : : SingletonClass* SingletonRef< SingletonClass >::m_pInstance = 0;
189 : :
190 : : template< class SingletonClass >
191 : : sal_Int32 SingletonRef< SingletonClass >::m_nRef = 0;
192 : :
193 : : } // namespace salhelper
194 : :
195 : : #endif // _SALHELPER_SINGLETONREF_HXX_
196 : :
197 : : /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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