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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 constant.hpp | |
9 | * \author Andrey Semashev | |
10 | * \date 15.04.2007 | |
11 | * | |
12 | * The header contains implementation of a constant attribute. | |
13 | */ | |
14 | ||
15 | #ifndef BOOST_LOG_ATTRIBUTES_CONSTANT_HPP_INCLUDED_ | |
16 | #define BOOST_LOG_ATTRIBUTES_CONSTANT_HPP_INCLUDED_ | |
17 | ||
18 | #include <boost/move/core.hpp> | |
19 | #include <boost/move/utility_core.hpp> | |
20 | #include <boost/type_traits/remove_reference.hpp> | |
21 | #include <boost/log/detail/config.hpp> | |
22 | #include <boost/log/detail/embedded_string_type.hpp> | |
23 | #include <boost/log/attributes/attribute.hpp> | |
24 | #include <boost/log/attributes/attribute_cast.hpp> | |
25 | #include <boost/log/attributes/attribute_value_impl.hpp> | |
26 | #include <boost/log/detail/header.hpp> | |
27 | ||
28 | #ifdef BOOST_HAS_PRAGMA_ONCE | |
29 | #pragma once | |
30 | #endif | |
31 | ||
32 | namespace boost { | |
33 | ||
34 | BOOST_LOG_OPEN_NAMESPACE | |
35 | ||
36 | namespace attributes { | |
37 | ||
38 | /*! | |
39 | * \brief A class of an attribute that holds a single constant value | |
40 | * | |
41 | * The constant is a simplest and one of the most frequently used types of attributes. | |
42 | * It stores a constant value, which it eventually returns as its value each time | |
43 | * requested. | |
44 | */ | |
45 | template< typename T > | |
46 | class constant : | |
47 | public attribute | |
48 | { | |
49 | public: | |
50 | //! Attribute value type | |
51 | typedef T value_type; | |
52 | ||
53 | protected: | |
54 | //! Factory implementation | |
55 | class BOOST_SYMBOL_VISIBLE impl : | |
56 | public attribute_value_impl< value_type > | |
57 | { | |
58 | //! Base type | |
59 | typedef attribute_value_impl< value_type > base_type; | |
60 | ||
61 | public: | |
62 | /*! | |
63 | * Constructor with the stored value initialization | |
64 | */ | |
65 | explicit impl(value_type const& value) : base_type(value) {} | |
66 | /*! | |
67 | * Constructor with the stored value initialization | |
68 | */ | |
69 | explicit impl(BOOST_RV_REF(value_type) value) : base_type(boost::move(value)) {} | |
70 | }; | |
71 | ||
72 | public: | |
73 | /*! | |
74 | * Constructor with the stored value initialization | |
75 | */ | |
76 | explicit constant(value_type const& value) : attribute(new impl(value)) {} | |
77 | /*! | |
78 | * Constructor with the stored value initialization | |
79 | */ | |
80 | explicit constant(BOOST_RV_REF(value_type) value) : attribute(new impl(boost::move(value))) {} | |
81 | /*! | |
82 | * Constructor for casting support | |
83 | */ | |
84 | explicit constant(cast_source const& source) : attribute(source.as< impl >()) | |
85 | { | |
86 | } | |
87 | ||
88 | /*! | |
89 | * \return Reference to the contained value. | |
90 | */ | |
91 | value_type const& get() const | |
92 | { | |
93 | return static_cast< impl* >(this->get_impl())->get(); | |
94 | } | |
95 | }; | |
96 | ||
97 | /*! | |
98 | * The function constructs a \c constant attribute containing the provided value. | |
99 | * The function automatically converts C string arguments to \c std::basic_string objects. | |
100 | */ | |
101 | template< typename T > | |
102 | inline constant< | |
103 | typename boost::log::aux::make_embedded_string_type< | |
104 | typename remove_reference< T >::type | |
105 | >::type | |
106 | > make_constant(BOOST_FWD_REF(T) val) | |
107 | { | |
108 | typedef typename boost::log::aux::make_embedded_string_type< | |
109 | typename remove_reference< T >::type | |
110 | >::type value_type; | |
111 | return constant< value_type >(boost::forward< T >(val)); | |
112 | } | |
113 | ||
114 | } // namespace attributes | |
115 | ||
116 | BOOST_LOG_CLOSE_NAMESPACE // namespace log | |
117 | ||
118 | } // namespace boost | |
119 | ||
120 | #include <boost/log/detail/footer.hpp> | |
121 | ||
122 | #endif // BOOST_LOG_ATTRIBUTES_CONSTANT_HPP_INCLUDED_ |