1 | /* |
2 | * Copyright Andrey Semashev 2007 - 2015. |
3 | * Distributed under the Boost Software License, Version 1.0. |
4 | * (See accompanying file LICENSE_1_0.txt or copy at |
5 | * http://www.boost.org/LICENSE_1_0.txt) |
6 | */ |
7 | /*! |
8 | * \file singleton.hpp |
9 | * \author Andrey Semashev |
10 | * \date 20.04.2008 |
11 | * |
12 | * \brief This header is the Boost.Log library implementation, see the library documentation |
13 | * at http://www.boost.org/doc/libs/release/libs/log/doc/html/index.html. |
14 | */ |
15 | |
16 | #ifndef BOOST_LOG_DETAIL_SINGLETON_HPP_INCLUDED_ |
17 | #define BOOST_LOG_DETAIL_SINGLETON_HPP_INCLUDED_ |
18 | |
19 | #include <boost/log/detail/config.hpp> |
20 | #include <boost/log/utility/once_block.hpp> |
21 | #include <boost/log/detail/header.hpp> |
22 | |
23 | #ifdef BOOST_HAS_PRAGMA_ONCE |
24 | #pragma once |
25 | #endif |
26 | |
27 | namespace boost { |
28 | |
29 | BOOST_LOG_OPEN_NAMESPACE |
30 | |
31 | namespace aux { |
32 | |
33 | //! A base class for singletons, constructed on-demand |
34 | template< typename DerivedT, typename StorageT = DerivedT > |
35 | class lazy_singleton |
36 | { |
37 | public: |
38 | BOOST_DEFAULTED_FUNCTION(lazy_singleton(), {}) |
39 | |
40 | //! Returns the singleton instance |
41 | static StorageT& get() |
42 | { |
43 | BOOST_LOG_ONCE_BLOCK() |
44 | { |
45 | DerivedT::init_instance(); |
46 | } |
47 | return get_instance(); |
48 | } |
49 | |
50 | //! Initializes the singleton instance |
51 | static void init_instance() |
52 | { |
53 | get_instance(); |
54 | } |
55 | |
56 | BOOST_DELETED_FUNCTION(lazy_singleton(lazy_singleton const&)) |
57 | BOOST_DELETED_FUNCTION(lazy_singleton& operator= (lazy_singleton const&)) |
58 | |
59 | protected: |
60 | //! Returns the singleton instance (not thread-safe) |
61 | static StorageT& get_instance() |
62 | { |
63 | static StorageT instance; |
64 | return instance; |
65 | } |
66 | }; |
67 | |
68 | //! A base class for singletons, constructed on namespace scope initialization stage |
69 | template< typename DerivedT, typename StorageT = DerivedT > |
70 | class singleton : |
71 | public lazy_singleton< DerivedT, StorageT > |
72 | { |
73 | public: |
74 | static StorageT& instance; |
75 | }; |
76 | |
77 | template< typename DerivedT, typename StorageT > |
78 | StorageT& singleton< DerivedT, StorageT >::instance = |
79 | lazy_singleton< DerivedT, StorageT >::get(); |
80 | |
81 | } // namespace aux |
82 | |
83 | BOOST_LOG_CLOSE_NAMESPACE // namespace log |
84 | |
85 | } // namespace boost |
86 | |
87 | #include <boost/log/detail/footer.hpp> |
88 | |
89 | #endif // BOOST_LOG_DETAIL_SINGLETON_HPP_INCLUDED_ |
90 | |