log/attributes/value_extraction_fwd.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   value_extraction_fwd.hpp
0009  * \author Andrey Semashev
0010  * \date   01.03.2008
0011  *
0012  * The header contains forward declaration of tools for extracting attribute values
0013  * from the view.
0014  */
0015
0016 #ifndef BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_FWD_HPP_INCLUDED_
0017 #define BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_FWD_HPP_INCLUDED_
0018
0019 #include <boost/log/detail/config.hpp>
0020 #include <boost/log/attributes/fallback_policy_fwd.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 result_of {
0031
0032 /*!
0033  * \brief A metafunction that allows to acquire the result of the value extraction
0034  */
0035 template< typename T, typename DefaultT = T, typename TagT = void >
0036 struct extract_or_default;
0037
0038 /*!
0039  * \brief A metafunction that allows to acquire the result of the value extraction
0040  */
0041 template< typename T, typename TagT = void >
0042 struct extract_or_throw;
0043
0044 /*!
0045  * \brief A metafunction that allows to acquire the result of the value extraction
0046  */
0047 template< typename T, typename TagT = void >
0048 struct extract;
0049
0050 } // namespace result_of
0051
0052 /*!
0053  * \brief Generic attribute value extractor
0054  */
0055 template< typename T, typename FallbackPolicyT = fallback_to_none, typename TagT = void >
0056 class value_extractor;
0057
0058 BOOST_LOG_CLOSE_NAMESPACE // namespace log
0059
0060 } // namespace boost
0061
0062 #endif // BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_FWD_HPP_INCLUDED_