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 sinks/frontend_requirements.hpp
9 * \author Andrey Semashev
10 * \date 22.04.2007
11 *
12 * The header contains definition of requirement tags that sink backend may declare
13 * with regard to frontends. These requirements ensure that a backend will not
14 * be used with an incompatible frontend.
15 */
16
17#ifndef BOOST_LOG_SINKS_FRONTEND_REQUIREMENTS_HPP_INCLUDED_
18#define BOOST_LOG_SINKS_FRONTEND_REQUIREMENTS_HPP_INCLUDED_
19
20#include <boost/type_traits/is_base_of.hpp>
21#include <boost/log/detail/config.hpp>
22#if defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
23#include <boost/mpl/aux_/na.hpp>
24#include <boost/mpl/placeholders.hpp>
25#include <boost/mpl/inherit.hpp>
26#include <boost/mpl/inherit_linearly.hpp>
27#include <boost/mpl/vector.hpp>
28#include <boost/preprocessor/repetition/enum_params.hpp>
29#include <boost/preprocessor/repetition/enum_params_with_a_default.hpp>
30#endif
31#include <boost/log/detail/header.hpp>
32
33#ifdef BOOST_HAS_PRAGMA_ONCE
34#pragma once
35#endif
36
37#ifndef BOOST_LOG_COMBINE_REQUIREMENTS_LIMIT
38//! The macro specifies the maximum number of requirements that can be combined with the \c combine_requirements metafunction
39#define BOOST_LOG_COMBINE_REQUIREMENTS_LIMIT 5
40#endif
41
42namespace boost {
43
44BOOST_LOG_OPEN_NAMESPACE
45
46namespace sinks {
47
48/*!
49 * The sink backend expects pre-synchronized calls, all needed synchronization is implemented
50 * in the frontend (IOW, only one thread is feeding records to the backend concurrently, but
51 * it is possible for several threads to write sequentially). Note that if a frontend supports
52 * synchronized record feeding, it will also report capable of concurrent record feeding.
53 */
54struct synchronized_feeding {};
55
56#if !defined(BOOST_LOG_NO_THREADS)
57
58/*!
59 * The sink backend ensures all needed synchronization, it is capable to handle multithreaded calls
60 */
61struct concurrent_feeding : synchronized_feeding {};
62
63#else // !defined(BOOST_LOG_NO_THREADS)
64
65// If multithreading is disabled, threading models become redundant
66typedef synchronized_feeding concurrent_feeding;
67
68#endif // !defined(BOOST_LOG_NO_THREADS)
69
70/*!
71 * The sink backend requires the frontend to perform log record formatting before feeding
72 */
73struct formatted_records {};
74
75/*!
76 * The sink backend supports flushing
77 */
78struct flushing {};
79
80#if defined(BOOST_LOG_DOXYGEN_PASS)
81
82/*!
83 * The metafunction combines multiple requirement tags into one type. The resulting type will
84 * satisfy all specified requirements (i.e. \c has_requirement metafunction will return positive result).
85 */
86template< typename... RequirementsT >
87struct combine_requirements;
88
89#elif !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
90
91namespace aux {
92
93template< typename... RequirementsT >
94struct combined_requirements :
95 public RequirementsT...
96{
97};
98
99} // namespace aux
100
101template< typename... RequirementsT >
102struct combine_requirements
103{
104 typedef sinks::aux::combined_requirements< RequirementsT... > type;
105};
106
107#else
108
109template< BOOST_PP_ENUM_PARAMS_WITH_A_DEFAULT(BOOST_LOG_COMBINE_REQUIREMENTS_LIMIT, typename ReqT, mpl::na) >
110struct combine_requirements :
111 mpl::inherit_linearly<
112 mpl::vector< BOOST_PP_ENUM_PARAMS(BOOST_LOG_COMBINE_REQUIREMENTS_LIMIT, ReqT) >,
113 mpl::inherit2< mpl::_1, mpl::_2 >
114 >
115{
116};
117
118#endif // BOOST_LOG_DOXYGEN_PASS
119
120/*!
121 * A helper metafunction to check if a requirement is satisfied. The \c TestedT template argument
122 * should be the type combining one or several requirements and \c RequiredT is the requirement
123 * to test against. The metafunction will yield a positive result if \c TestedT supports \c RequiredT.
124 */
125template< typename TestedT, typename RequiredT >
126struct has_requirement :
127 public is_base_of< RequiredT, TestedT >
128{
129};
130
131} // namespace sinks
132
133BOOST_LOG_CLOSE_NAMESPACE // namespace log
134
135} // namespace boost
136
137#include <boost/log/detail/footer.hpp>
138
139#endif // BOOST_LOG_SINKS_FRONTEND_REQUIREMENTS_HPP_INCLUDED_
140

source code of boost/libs/log/include/boost/log/sinks/frontend_requirements.hpp