279 lines
8.7 KiB
C++
279 lines
8.7 KiB
C++
/*
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* Copyright Andrey Semashev 2007 - 2015.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*/
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/*!
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* \file attr.hpp
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* \author Andrey Semashev
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* \date 21.07.2012
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*
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* The header contains implementation of a generic attribute placeholder in template expressions.
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*/
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#ifndef BOOST_LOG_EXPRESSIONS_ATTR_HPP_INCLUDED_
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#define BOOST_LOG_EXPRESSIONS_ATTR_HPP_INCLUDED_
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#include <boost/mpl/bool.hpp>
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#include <boost/utility/result_of.hpp>
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#include <boost/phoenix/core/actor.hpp>
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#include <boost/phoenix/core/terminal_fwd.hpp>
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#include <boost/phoenix/core/is_nullary.hpp>
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#include <boost/phoenix/core/environment.hpp>
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#include <boost/fusion/sequence/intrinsic/at_c.hpp>
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#include <boost/type_traits/remove_cv.hpp>
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#include <boost/type_traits/remove_reference.hpp>
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#include <boost/log/detail/config.hpp>
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#include <boost/log/detail/copy_cv.hpp>
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#include <boost/log/detail/custom_terminal_spec.hpp>
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#include <boost/log/attributes/attribute_name.hpp>
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#include <boost/log/attributes/value_extraction.hpp>
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#include <boost/log/attributes/fallback_policy.hpp>
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#include <boost/log/expressions/attr_fwd.hpp>
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#include <boost/log/detail/header.hpp>
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#ifdef BOOST_HAS_PRAGMA_ONCE
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#pragma once
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#endif
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namespace boost {
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BOOST_LOG_OPEN_NAMESPACE
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namespace expressions {
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/*!
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* An attribute value extraction terminal
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*/
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template< typename T, typename FallbackPolicyT, typename TagT >
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class attribute_terminal
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{
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private:
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//! Value extractor type
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typedef value_extractor< T, FallbackPolicyT, TagT > value_extractor_type;
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//! Self type
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typedef attribute_terminal< T, FallbackPolicyT, TagT > this_type;
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public:
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#ifndef BOOST_LOG_DOXYGEN_PASS
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//! Internal typedef for type categorization
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typedef void _is_boost_log_terminal;
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#endif
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//! Attribute tag type
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typedef TagT tag_type;
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//! Attribute value type
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typedef typename value_extractor_type::value_type value_type;
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//! Fallback policy type
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typedef typename value_extractor_type::fallback_policy fallback_policy;
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//! Function result type
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template< typename >
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struct result;
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template< typename ThisT, typename ContextT >
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struct result< ThisT(ContextT) >
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{
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typedef typename remove_cv<
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typename remove_reference< typename phoenix::result_of::env< ContextT >::type >::type
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>::type env_type;
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typedef typename env_type::args_type args_type;
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typedef typename boost::log::aux::copy_cv< ThisT, value_extractor_type >::type cv_value_extractor_type;
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typedef typename boost::result_of< cv_value_extractor_type(attribute_name const&, typename fusion::result_of::at_c< args_type, 0 >::type) >::type type;
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};
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private:
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//! Attribute value name
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const attribute_name m_name;
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//! Attribute value extractor
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value_extractor_type m_value_extractor;
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public:
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/*!
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* Initializing constructor
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*/
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explicit attribute_terminal(attribute_name const& name) : m_name(name)
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{
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}
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/*!
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* Initializing constructor
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*/
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template< typename U >
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attribute_terminal(attribute_name const& name, U const& arg) : m_name(name), m_value_extractor(arg)
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{
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}
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/*!
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* \returns Attribute value name
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*/
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attribute_name get_name() const
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{
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return m_name;
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}
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/*!
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* \returns Fallback policy
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*/
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fallback_policy const& get_fallback_policy() const
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{
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return m_value_extractor.get_fallback_policy();
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}
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/*!
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* The operator extracts attribute value
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*/
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template< typename ContextT >
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typename result< this_type(ContextT const&) >::type
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operator() (ContextT const& ctx)
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{
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return m_value_extractor(m_name, fusion::at_c< 0 >(phoenix::env(ctx).args()));
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}
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/*!
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* The operator extracts attribute value
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*/
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template< typename ContextT >
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typename result< const this_type(ContextT const&) >::type
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operator() (ContextT const& ctx) const
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{
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return m_value_extractor(m_name, fusion::at_c< 0 >(phoenix::env(ctx).args()));
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}
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BOOST_DELETED_FUNCTION(attribute_terminal())
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};
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/*!
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* An attribute value extraction terminal actor
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*/
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template< typename T, typename FallbackPolicyT, typename TagT, template< typename > class ActorT >
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class attribute_actor :
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public ActorT< attribute_terminal< T, FallbackPolicyT, TagT > >
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{
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public:
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//! Attribute tag type
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typedef TagT tag_type;
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//! Fallback policy
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typedef FallbackPolicyT fallback_policy;
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//! Base terminal type
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typedef attribute_terminal< T, fallback_policy, tag_type > terminal_type;
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//! Attribute value type
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typedef typename terminal_type::value_type value_type;
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//! Base actor type
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typedef ActorT< terminal_type > base_type;
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public:
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//! Initializing constructor
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explicit attribute_actor(base_type const& act) : base_type(act)
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{
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}
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/*!
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* \returns The attribute name
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*/
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attribute_name get_name() const
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{
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return this->proto_expr_.child0.get_name();
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}
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/*!
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* \returns Fallback policy
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*/
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fallback_policy const& get_fallback_policy() const
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{
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return this->proto_expr_.child0.get_fallback_policy();
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}
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//! Expression with cached attribute name
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typedef attribute_actor< value_type, fallback_to_none, tag_type, ActorT > or_none_result_type;
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//! Generates an expression that extracts the attribute value or a default value
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or_none_result_type or_none() const
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{
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typedef typename or_none_result_type::terminal_type result_terminal;
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typename or_none_result_type::base_type act = {{ result_terminal(get_name()) }};
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return or_none_result_type(act);
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}
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//! Expression with cached attribute name
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typedef attribute_actor< value_type, fallback_to_throw, tag_type, ActorT > or_throw_result_type;
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//! Generates an expression that extracts the attribute value or throws an exception
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or_throw_result_type or_throw() const
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{
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typedef typename or_throw_result_type::terminal_type result_terminal;
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typename or_throw_result_type::base_type act = {{ result_terminal(get_name()) }};
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return or_throw_result_type(act);
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}
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//! Generates an expression that extracts the attribute value or a default value
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template< typename DefaultT >
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attribute_actor< value_type, fallback_to_default< DefaultT >, tag_type, ActorT > or_default(DefaultT const& def_val) const
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{
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typedef attribute_actor< value_type, fallback_to_default< DefaultT >, tag_type, ActorT > or_default_result_type;
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typedef typename or_default_result_type::terminal_type result_terminal;
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typename or_default_result_type::base_type act = {{ result_terminal(get_name(), def_val) }};
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return or_default_result_type(act);
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}
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};
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/*!
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* The function generates a terminal node in a template expression. The node will extract the value of the attribute
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* with the specified name and type.
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*/
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template< typename AttributeValueT >
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BOOST_FORCEINLINE attribute_actor< AttributeValueT > attr(attribute_name const& name)
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{
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typedef attribute_actor< AttributeValueT > result_type;
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typedef typename result_type::terminal_type result_terminal;
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typename result_type::base_type act = {{ result_terminal(name) }};
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return result_type(act);
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}
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/*!
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* The function generates a terminal node in a template expression. The node will extract the value of the attribute
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* with the specified name and type.
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*/
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template< typename AttributeValueT, typename TagT >
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BOOST_FORCEINLINE attribute_actor< AttributeValueT, fallback_to_none, TagT > attr(attribute_name const& name)
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{
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typedef attribute_actor< AttributeValueT, fallback_to_none, TagT > result_type;
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typedef typename result_type::terminal_type result_terminal;
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typename result_type::base_type act = {{ result_terminal(name) }};
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return result_type(act);
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}
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} // namespace expressions
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BOOST_LOG_CLOSE_NAMESPACE // namespace log
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#ifndef BOOST_LOG_DOXYGEN_PASS
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namespace phoenix {
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namespace result_of {
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template< typename T, typename FallbackPolicyT, typename TagT >
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struct is_nullary< custom_terminal< boost::log::expressions::attribute_terminal< T, FallbackPolicyT, TagT > > > :
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public mpl::false_
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{
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};
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} // namespace result_of
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} // namespace phoenix
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#endif
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} // namespace boost
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#include <boost/log/detail/footer.hpp>
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#if defined(BOOST_LOG_EXPRESSIONS_FORMATTERS_STREAM_HPP_INCLUDED_)
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#include <boost/log/detail/attr_output_impl.hpp>
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#endif
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#endif // BOOST_LOG_EXPRESSIONS_ATTR_HPP_INCLUDED_
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