log/expressions/is_keyword_descriptor.hpp

0001 /*
0002  *          Copyright Andrey Semashev 2007 - 2015.
0003  * Distributed under the Boost Software License, Version 1.0.
0004  *    (See accompanying file LICENSE_1_0.txt or copy at
0005  *          http://www.boost.org/LICENSE_1_0.txt)
0006  */
0007 /*!
0008  * \file   is_keyword_descriptor.hpp
0009  * \author Andrey Semashev
0010  * \date   14.07.2012
0011  *
0012  * The header contains attribute keyword descriptor detection trait.
0013  */
0014
0015 #ifndef BOOST_LOG_EXPRESSIONS_IS_KEYWORD_DESCRIPTOR_HPP_INCLUDED_
0016 #define BOOST_LOG_EXPRESSIONS_IS_KEYWORD_DESCRIPTOR_HPP_INCLUDED_
0017
0018 #include <boost/mpl/bool.hpp>
0019 #include <boost/log/detail/config.hpp>
0020 #include <boost/log/detail/header.hpp>
0021
0022 #ifdef BOOST_HAS_PRAGMA_ONCE
0023 #pragma once
0024 #endif
0025
0026 namespace boost {
0027
0028 BOOST_LOG_OPEN_NAMESPACE
0029
0030 namespace expressions {
0031
0032 /*!
0033  * Base class for keyword descriptors. All keyword descriptors must derive from this class to support the \c is_keyword_descriptor trait.
0034  */
0035 struct keyword_descriptor
0036 {
0037 #ifndef BOOST_LOG_DOXYGEN_PASS
0038     typedef void _is_boost_log_keyword_descriptor;
0039 #endif // BOOST_LOG_DOXYGEN_PASS
0040 };
0041
0042 /*!
0043  * The metafunction detects if the type \c T is a keyword descriptor
0044  */
0045 template< typename T, typename VoidT = void >
0046 struct is_keyword_descriptor :
0047     public mpl::false_
0048 {
0049 };
0050
0051 #ifndef BOOST_LOG_DOXYGEN_PASS
0052 template< typename T >
0053 struct is_keyword_descriptor< T, typename T::_is_boost_log_keyword_descriptor > :
0054     public mpl::true_
0055 {
0056 };
0057 #endif
0058
0059 } // namespace expressions
0060
0061 BOOST_LOG_CLOSE_NAMESPACE // namespace log
0062
0063 } // namespace boost
0064
0065 #include <boost/log/detail/footer.hpp>
0066
0067 #endif // BOOST_LOG_EXPRESSIONS_IS_KEYWORD_DESCRIPTOR_HPP_INCLUDED_