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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 function.hpp | |
9 | * \author Andrey Semashev | |
10 | * \date 24.06.2007 | |
11 | * | |
12 | * The header contains implementation of an attribute that calls a third-party function on value acquisition. | |
13 | */ | |
14 | ||
15 | #ifndef BOOST_LOG_ATTRIBUTES_FUNCTION_HPP_INCLUDED_ | |
16 | #define BOOST_LOG_ATTRIBUTES_FUNCTION_HPP_INCLUDED_ | |
17 | ||
18 | #include <boost/static_assert.hpp> | |
19 | #include <boost/utility/result_of.hpp> | |
20 | #include <boost/type_traits/is_void.hpp> | |
21 | #include <boost/type_traits/remove_cv.hpp> | |
22 | #include <boost/type_traits/remove_reference.hpp> | |
23 | #include <boost/log/detail/config.hpp> | |
24 | #include <boost/log/attributes/attribute.hpp> | |
25 | #include <boost/log/attributes/attribute_cast.hpp> | |
26 | #include <boost/log/attributes/attribute_value_impl.hpp> | |
27 | #include <boost/log/detail/header.hpp> | |
28 | ||
29 | #ifdef BOOST_HAS_PRAGMA_ONCE | |
30 | #pragma once | |
31 | #endif | |
32 | ||
33 | namespace boost { | |
34 | ||
35 | BOOST_LOG_OPEN_NAMESPACE | |
36 | ||
37 | namespace attributes { | |
38 | ||
39 | /*! | |
40 | * \brief A class of an attribute that acquires its value from a third-party function object | |
41 | * | |
42 | * The attribute calls a stored nullary function object to acquire each value. | |
43 | * The result type of the function object is the attribute value type. | |
44 | * | |
45 | * It is not recommended to use this class directly. Use \c make_function convenience functions | |
46 | * to construct the attribute instead. | |
47 | */ | |
48 | template< typename R > | |
49 | class function : | |
50 | public attribute | |
51 | { | |
52 | BOOST_STATIC_ASSERT_MSG(!is_void< R >::value, "Boost.Log: Function object return type must not be void"); | |
53 | ||
54 | public: | |
55 | //! The attribute value type | |
56 | typedef R value_type; | |
57 | ||
58 | protected: | |
59 | //! Base class for factory implementation | |
60 | class BOOST_LOG_NO_VTABLE BOOST_SYMBOL_VISIBLE impl : | |
61 | public attribute::impl | |
62 | { | |
63 | }; | |
64 | ||
65 | //! Factory implementation | |
66 | template< typename T > | |
67 | class impl_template : | |
68 | public impl | |
69 | { | |
70 | private: | |
71 | //! Functor that returns attribute values | |
72 | /*! | |
73 | * \note The constness signifies that the function object should avoid | |
74 | * modifying its state since it's not protected against concurrent calls. | |
75 | */ | |
76 | const T m_Functor; | |
77 | ||
78 | public: | |
79 | /*! | |
80 | * Constructor with the stored delegate initialization | |
81 | */ | |
82 | explicit impl_template(T const& fun) : m_Functor(fun) {} | |
83 | ||
84 | attribute_value get_value() | |
85 | { | |
86 | return attributes::make_attribute_value(m_Functor()); | |
87 | } | |
88 | }; | |
89 | ||
90 | public: | |
91 | /*! | |
92 | * Initializing constructor | |
93 | */ | |
94 | template< typename T > | |
95 | explicit function(T const& fun) : attribute(new impl_template< T >(fun)) | |
96 | { | |
97 | } | |
98 | /*! | |
99 | * Constructor for casting support | |
100 | */ | |
101 | explicit function(cast_source const& source) : | |
102 | attribute(source.as< impl >()) | |
103 | { | |
104 | } | |
105 | }; | |
106 | ||
107 | #ifndef BOOST_NO_RESULT_OF | |
108 | ||
109 | /*! | |
110 | * The function constructs \c function attribute instance with the provided function object. | |
111 | * | |
112 | * \param fun Nullary functional object that returns an actual stored value for an attribute value. | |
113 | * \return Pointer to the attribute instance | |
114 | */ | |
115 | template< typename T > | |
116 | inline function< | |
117 | typename remove_cv< | |
118 | typename remove_reference< | |
119 | typename boost::result_of< T() >::type | |
120 | >::type | |
121 | >::type | |
122 | > make_function(T const& fun) | |
123 | { | |
124 | typedef typename remove_cv< | |
125 | typename remove_reference< | |
126 | typename boost::result_of< T() >::type | |
127 | >::type | |
128 | >::type result_type; | |
129 | ||
130 | typedef function< result_type > function_type; | |
131 | return function_type(fun); | |
132 | } | |
133 | ||
134 | #endif // BOOST_NO_RESULT_OF | |
135 | ||
136 | #ifndef BOOST_LOG_DOXYGEN_PASS | |
137 | ||
138 | /*! | |
139 | * The function constructs \c function attribute instance with the provided function object. | |
140 | * Use this version if your compiler fails to determine the result type of the function object. | |
141 | * | |
142 | * \param fun Nullary functional object that returns an actual stored value for an attribute value. | |
143 | * \return Pointer to the attribute instance | |
144 | */ | |
145 | template< typename R, typename T > | |
146 | inline function< | |
147 | typename remove_cv< | |
148 | typename remove_reference< R >::type | |
149 | >::type | |
150 | > make_function(T const& fun) | |
151 | { | |
152 | typedef typename remove_cv< | |
153 | typename remove_reference< R >::type | |
154 | >::type result_type; | |
155 | ||
156 | typedef function< result_type > function_type; | |
157 | return function_type(fun); | |
158 | } | |
159 | ||
160 | #endif // BOOST_LOG_DOXYGEN_PASS | |
161 | ||
162 | } // namespace attributes | |
163 | ||
164 | BOOST_LOG_CLOSE_NAMESPACE // namespace log | |
165 | ||
166 | } // namespace boost | |
167 | ||
168 | #include <boost/log/detail/footer.hpp> | |
169 | ||
170 | #endif // BOOST_LOG_ATTRIBUTES_FUNCTOR_HPP_INCLUDED_ |