Chris@16: /*
Chris@101:  *          Copyright Andrey Semashev 2007 - 2015.
Chris@16:  * Distributed under the Boost Software License, Version 1.0.
Chris@16:  *    (See accompanying file LICENSE_1_0.txt or copy at
Chris@16:  *          http://www.boost.org/LICENSE_1_0.txt)
Chris@16:  */
Chris@16: /*!
Chris@16:  * \file   value_extraction.hpp
Chris@16:  * \author Andrey Semashev
Chris@16:  * \date   01.03.2008
Chris@16:  *
Chris@16:  * The header contains implementation of tools for extracting an attribute value
Chris@16:  * from the view.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_HPP_INCLUDED_
Chris@16: #define BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_HPP_INCLUDED_
Chris@16: 
Chris@16: #include <boost/mpl/vector.hpp>
Chris@16: #include <boost/mpl/joint_view.hpp>
Chris@16: #include <boost/mpl/if.hpp>
Chris@16: #include <boost/mpl/eval_if.hpp>
Chris@16: #include <boost/mpl/identity.hpp>
Chris@16: #include <boost/mpl/is_sequence.hpp>
Chris@16: #include <boost/mpl/contains.hpp>
Chris@16: #include <boost/mpl/push_back.hpp>
Chris@16: #include <boost/type_traits/is_same.hpp>
Chris@16: #include <boost/utility/enable_if.hpp>
Chris@16: #include <boost/log/detail/config.hpp>
Chris@16: #include <boost/log/exceptions.hpp>
Chris@16: #include <boost/log/core/record.hpp>
Chris@16: #include <boost/log/attributes/attribute_name.hpp>
Chris@16: #include <boost/log/attributes/attribute_value.hpp>
Chris@16: #include <boost/log/attributes/attribute.hpp>
Chris@16: #include <boost/log/attributes/attribute_value_set.hpp>
Chris@16: #include <boost/log/attributes/value_extraction_fwd.hpp>
Chris@16: #include <boost/log/attributes/fallback_policy.hpp>
Chris@16: #include <boost/log/expressions/keyword_fwd.hpp>
Chris@16: #include <boost/log/utility/value_ref.hpp>
Chris@16: #include <boost/log/utility/type_dispatch/static_type_dispatcher.hpp>
Chris@16: #include <boost/log/detail/header.hpp>
Chris@16: 
Chris@16: #ifdef BOOST_HAS_PRAGMA_ONCE
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: BOOST_LOG_OPEN_NAMESPACE
Chris@16: 
Chris@16: namespace result_of {
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief A metafunction that allows to acquire the result of the value extraction
Chris@16:  *
Chris@16:  * The metafunction results in a type that is in form of <tt>T const&</tt>, if \c T is
Chris@16:  * not an MPL type sequence and <tt>DefaultT</tt> is the same as <tt>T</tt>,
Chris@16:  * or <tt>value_ref< TypesT, TagT ></tt> otherwise, with
Chris@16:  * \c TypesT being a type sequence comprising the types from sequence \c T and \c DefaultT,
Chris@16:  * if it is not present in \c T already.
Chris@16:  */
Chris@16: template< typename T, typename DefaultT, typename TagT >
Chris@16: struct extract_or_default
Chris@16: {
Chris@16:     typedef typename mpl::eval_if<
Chris@16:         mpl::is_sequence< T >,
Chris@16:         mpl::eval_if<
Chris@16:             mpl::contains< T, DefaultT >,
Chris@16:             mpl::identity< T >,
Chris@16:             mpl::push_back< T, DefaultT >
Chris@16:         >,
Chris@16:         mpl::if_<
Chris@16:             is_same< T, DefaultT >,
Chris@16:             T,
Chris@16:             mpl::vector2< T, DefaultT >
Chris@16:         >
Chris@16:     >::type extracted_type;
Chris@16: 
Chris@16:     typedef typename mpl::if_<
Chris@16:         mpl::is_sequence< extracted_type >,
Chris@16:         value_ref< extracted_type, TagT >,
Chris@16:         extracted_type const&
Chris@16:     >::type type;
Chris@16: };
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief A metafunction that allows to acquire the result of the value extraction
Chris@16:  *
Chris@16:  * The metafunction results in a type that is in form of <tt>T const&</tt>, if \c T is
Chris@16:  * not an MPL type sequence, or <tt>value_ref< T, TagT ></tt> otherwise. In the latter
Chris@16:  * case the value reference shall never be empty.
Chris@16:  */
Chris@16: template< typename T, typename TagT >
Chris@16: struct extract_or_throw
Chris@16: {
Chris@16:     typedef typename mpl::if_<
Chris@16:         mpl::is_sequence< T >,
Chris@16:         value_ref< T, TagT >,
Chris@16:         T const&
Chris@16:     >::type type;
Chris@16: };
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief A metafunction that allows to acquire the result of the value extraction
Chris@16:  *
Chris@16:  * The metafunction results in a type that is in form of <tt>value_ref< T, TagT ></tt>.
Chris@16:  */
Chris@16: template< typename T, typename TagT >
Chris@16: struct extract
Chris@16: {
Chris@16:     typedef value_ref< T, TagT > type;
Chris@16: };
Chris@16: 
Chris@16: } // namespace result_of
Chris@16: 
Chris@16: namespace aux {
Chris@16: 
Chris@16: //! The function object initializes the value reference
Chris@16: template< typename RefT >
Chris@16: struct value_ref_initializer
Chris@16: {
Chris@16:     typedef void result_type;
Chris@16: 
Chris@16:     value_ref_initializer(RefT& ref) : m_ref(ref)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     template< typename ArgT >
Chris@16:     result_type operator() (ArgT const& arg) const
Chris@16:     {
Chris@16:         m_ref = RefT(arg);
Chris@16:     }
Chris@16: 
Chris@16: private:
Chris@16:     RefT& m_ref;
Chris@16: };
Chris@16: 
Chris@16: //! The function unwraps \c value_ref, if possible
Chris@16: template< typename T, typename TagT >
Chris@16: BOOST_FORCEINLINE typename enable_if< mpl::is_sequence< T >, value_ref< T, TagT > >::type
Chris@16: unwrap_value_ref(value_ref< T, TagT > const& r)
Chris@16: {
Chris@16:     return r;
Chris@16: }
Chris@16: 
Chris@16: template< typename T, typename TagT >
Chris@16: BOOST_FORCEINLINE typename disable_if< mpl::is_sequence< T >, T const& >::type
Chris@16: unwrap_value_ref(value_ref< T, TagT > const& r)
Chris@16: {
Chris@16:     return r.get();
Chris@16: }
Chris@16: 
Chris@16: } // namespace aux
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief Generic attribute value extractor
Chris@16:  *
Chris@16:  * Attribute value extractor is a functional object that attempts to find and extract the stored
Chris@16:  * attribute value from the attribute values view or a log record. The extracted value is returned
Chris@16:  * from the extractor.
Chris@16:  */
Chris@16: template< typename T, typename FallbackPolicyT, typename TagT >
Chris@16: class value_extractor :
Chris@16:     private FallbackPolicyT
Chris@16: {
Chris@16: public:
Chris@16:     //! Fallback policy
Chris@16:     typedef FallbackPolicyT fallback_policy;
Chris@16:     //! Attribute value types
Chris@16:     typedef T value_type;
Chris@16:     //! Function object result type
Chris@16:     typedef value_ref< value_type, TagT > result_type;
Chris@16: 
Chris@16: public:
Chris@16:     /*!
Chris@16:      * Default constructor
Chris@16:      */
Chris@16:     BOOST_DEFAULTED_FUNCTION(value_extractor(), {})
Chris@16: 
Chris@16:     /*!
Chris@16:      * Copy constructor
Chris@16:      */
Chris@16:     value_extractor(value_extractor const& that) : fallback_policy(static_cast< fallback_policy const& >(that))
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * Constructor
Chris@16:      *
Chris@16:      * \param arg Fallback policy constructor argument
Chris@16:      */
Chris@16:     template< typename U >
Chris@16:     explicit value_extractor(U const& arg) : fallback_policy(arg) {}
Chris@16: 
Chris@16:     /*!
Chris@16:      * Extraction operator. Attempts to acquire the stored value of one of the supported types. If extraction succeeds,
Chris@16:      * the extracted value is returned.
Chris@16:      *
Chris@16:      * \param attr The attribute value to extract from.
Chris@16:      * \return The extracted value, if extraction succeeded, an empty value otherwise.
Chris@16:      */
Chris@16:     result_type operator() (attribute_value const& attr) const
Chris@16:     {
Chris@16:         result_type res;
Chris@16:         aux::value_ref_initializer< result_type > initializer(res);
Chris@16:         if (!!attr)
Chris@16:         {
Chris@16:             static_type_dispatcher< value_type > disp(initializer);
Chris@16:             if (!attr.dispatch(disp) && !fallback_policy::apply_default(initializer))
Chris@16:                 fallback_policy::on_invalid_type(attr.get_type());
Chris@16:         }
Chris@16:         else if (!fallback_policy::apply_default(initializer))
Chris@16:         {
Chris@16:             fallback_policy::on_missing_value();
Chris@16:         }
Chris@16:         return res;
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * Extraction operator. Looks for an attribute value with the specified name
Chris@16:      * and tries to acquire the stored value of one of the supported types. If extraction succeeds,
Chris@16:      * the extracted value is returned.
Chris@16:      *
Chris@16:      * \param name Attribute value name.
Chris@16:      * \param attrs A set of attribute values in which to look for the specified attribute value.
Chris@16:      * \return The extracted value, if extraction succeeded, an empty value otherwise.
Chris@16:      */
Chris@16:     result_type operator() (attribute_name const& name, attribute_value_set const& attrs) const
Chris@16:     {
Chris@16:         try
Chris@16:         {
Chris@16:             attribute_value_set::const_iterator it = attrs.find(name);
Chris@16:             if (it != attrs.end())
Chris@16:                 return operator() (it->second);
Chris@16:             else
Chris@16:                 return operator() (attribute_value());
Chris@16:         }
Chris@16:         catch (exception& e)
Chris@16:         {
Chris@16:             // Attach the attribute name to the exception
Chris@16:             boost::log::aux::attach_attribute_name_info(e, name);
Chris@16:             throw;
Chris@16:         }
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * Extraction operator. Looks for an attribute value with the specified name
Chris@16:      * and tries to acquire the stored value of one of the supported types. If extraction succeeds,
Chris@16:      * the extracted value is returned.
Chris@16:      *
Chris@16:      * \param name Attribute value name.
Chris@16:      * \param rec A log record. The attribute value will be sought among those associated with the record.
Chris@16:      * \return The extracted value, if extraction succeeded, an empty value otherwise.
Chris@16:      */
Chris@16:     result_type operator() (attribute_name const& name, record const& rec) const
Chris@16:     {
Chris@16:         return operator() (name, rec.attribute_values());
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * Extraction operator. Looks for an attribute value with the specified name
Chris@16:      * and tries to acquire the stored value of one of the supported types. If extraction succeeds,
Chris@16:      * the extracted value is returned.
Chris@16:      *
Chris@16:      * \param name Attribute value name.
Chris@16:      * \param rec A log record view. The attribute value will be sought among those associated with the record.
Chris@16:      * \return The extracted value, if extraction succeeded, an empty value otherwise.
Chris@16:      */
Chris@16:     result_type operator() (attribute_name const& name, record_view const& rec) const
Chris@16:     {
Chris@16:         return operator() (name, rec.attribute_values());
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * \returns Fallback policy
Chris@16:      */
Chris@16:     fallback_policy const& get_fallback_policy() const
Chris@16:     {
Chris@16:         return *static_cast< fallback_policy const* >(this);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: #if !defined(BOOST_LOG_DOXYGEN_PASS)
Chris@16: #if !defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
Chris@16: #define BOOST_LOG_AUX_VOID_DEFAULT = void
Chris@16: #else
Chris@16: #define BOOST_LOG_AUX_VOID_DEFAULT
Chris@16: #endif
Chris@16: #endif // !defined(BOOST_LOG_DOXYGEN_PASS)
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param name The name of the attribute value to extract.
Chris@16:  * \param attrs A set of attribute values in which to look for the specified attribute value.
Chris@16:  * \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
Chris@16: inline typename result_of::extract< T, TagT >::type extract(attribute_name const& name, attribute_value_set const& attrs)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_none, TagT > extractor;
Chris@16:     return extractor(name, attrs);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param name The name of the attribute value to extract.
Chris@16:  * \param rec A log record. The attribute value will be sought among those associated with the record.
Chris@16:  * \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
Chris@16: inline typename result_of::extract< T, TagT >::type extract(attribute_name const& name, record const& rec)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_none, TagT > extractor;
Chris@16:     return extractor(name, rec);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param name The name of the attribute value to extract.
Chris@16:  * \param rec A log record view. The attribute value will be sought among those associated with the record.
Chris@16:  * \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
Chris@16: inline typename result_of::extract< T, TagT >::type extract(attribute_name const& name, record_view const& rec)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_none, TagT > extractor;
Chris@16:     return extractor(name, rec);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param value Attribute value.
Chris@16:  * \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
Chris@16: inline typename result_of::extract< T, TagT >::type extract(attribute_value const& value)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_none, TagT > extractor;
Chris@16:     return extractor(value);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param name The name of the attribute value to extract.
Chris@16:  * \param attrs A set of attribute values in which to look for the specified attribute value.
Chris@16:  * \return The extracted value or a non-empty \c value_ref that refers to the value.
Chris@16:  * \throws An exception is thrown if the requested value cannot be extracted.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
Chris@16: inline typename result_of::extract_or_throw< T, TagT >::type extract_or_throw(attribute_name const& name, attribute_value_set const& attrs)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_throw, TagT > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(name, attrs));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param name The name of the attribute value to extract.
Chris@16:  * \param rec A log record. The attribute value will be sought among those associated with the record.
Chris@16:  * \return The extracted value or a non-empty \c value_ref that refers to the value.
Chris@16:  * \throws An exception is thrown if the requested value cannot be extracted.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
Chris@16: inline typename result_of::extract_or_throw< T, TagT >::type extract_or_throw(attribute_name const& name, record const& rec)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_throw, TagT > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(name, rec));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param name The name of the attribute value to extract.
Chris@16:  * \param rec A log record view. The attribute value will be sought among those associated with the record.
Chris@16:  * \return The extracted value or a non-empty \c value_ref that refers to the value.
Chris@16:  * \throws An exception is thrown if the requested value cannot be extracted.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
Chris@16: inline typename result_of::extract_or_throw< T, TagT >::type extract_or_throw(attribute_name const& name, record_view const& rec)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_throw, TagT > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(name, rec));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param value Attribute value.
Chris@16:  * \return The extracted value or a non-empty \c value_ref that refers to the value.
Chris@16:  * \throws An exception is thrown if the requested value cannot be extracted.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
Chris@16: inline typename result_of::extract_or_throw< T, TagT >::type extract_or_throw(attribute_value const& value)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_throw, TagT > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(value));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \note Caution must be exercised if the default value is a temporary object. Because the function returns
Chris@16:  *       a reference, if the temporary object is destroyed, the reference may become dangling.
Chris@16:  *
Chris@16:  * \param name The name of the attribute value to extract.
Chris@16:  * \param attrs A set of attribute values in which to look for the specified attribute value.
Chris@16:  * \param def_val The default value
Chris@16:  * \return The extracted value, if found. The default value otherwise.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< T, DefaultT, TagT >::type
Chris@16: extract_or_default(attribute_name const& name, attribute_value_set const& attrs, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< T, DefaultT, TagT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& >, TagT > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(name, attrs));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be visited.
Chris@16:  *
Chris@16:  * \note Caution must be exercised if the default value is a temporary object. Because the function returns
Chris@16:  *       a reference, if the temporary object is destroyed, the reference may become dangling.
Chris@16:  *
Chris@16:  * \param name The name of the attribute value to extract.
Chris@16:  * \param rec A log record. The attribute value will be sought among those associated with the record.
Chris@16:  * \param def_val The default value
Chris@16:  * \return The extracted value, if found. The default value otherwise.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< T, DefaultT, TagT >::type
Chris@16: extract_or_default(attribute_name const& name, record const& rec, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< T, DefaultT, TagT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& >, TagT > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(name, rec));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be visited.
Chris@16:  *
Chris@16:  * \note Caution must be exercised if the default value is a temporary object. Because the function returns
Chris@16:  *       a reference, if the temporary object is destroyed, the reference may become dangling.
Chris@16:  *
Chris@16:  * \param name The name of the attribute value to extract.
Chris@16:  * \param rec A log record view. The attribute value will be sought among those associated with the record.
Chris@16:  * \param def_val The default value
Chris@16:  * \return The extracted value, if found. The default value otherwise.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< T, DefaultT, TagT >::type
Chris@16: extract_or_default(attribute_name const& name, record_view const& rec, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< T, DefaultT, TagT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& >, TagT > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(name, rec));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be visited.
Chris@16:  *
Chris@16:  * \note Caution must be exercised if the default value is a temporary object. Because the function returns
Chris@16:  *       a reference, if the temporary object is destroyed, the reference may become dangling.
Chris@16:  *
Chris@16:  * \param value Attribute value.
Chris@16:  * \param def_val The default value
Chris@16:  * \return The extracted value, if found. The default value otherwise.
Chris@16:  */
Chris@16: template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< T, DefaultT, TagT >::type extract_or_default(attribute_value const& value, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< T, DefaultT, TagT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& >, TagT > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(value));
Chris@16: }
Chris@16: 
Chris@16: #if defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract< T >::type extract(attribute_name const& name, attribute_value_set const& attrs)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_none > extractor;
Chris@16:     return extractor(name, attrs);
Chris@16: }
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract< T >::type extract(attribute_name const& name, record const& rec)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_none > extractor;
Chris@16:     return extractor(name, rec);
Chris@16: }
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract< T >::type extract(attribute_name const& name, record_view const& rec)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_none > extractor;
Chris@16:     return extractor(name, rec);
Chris@16: }
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract< T >::type extract(attribute_value const& value)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_none > extractor;
Chris@16:     return extractor(value);
Chris@16: }
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract_or_throw< T >::type extract_or_throw(attribute_name const& name, attribute_value_set const& attrs)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_throw > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(name, attrs));
Chris@16: }
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract_or_throw< T >::type extract_or_throw(attribute_name const& name, record const& rec)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_throw > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(name, rec));
Chris@16: }
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract_or_throw< T >::type extract_or_throw(attribute_name const& name, record_view const& rec)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_throw > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(name, rec));
Chris@16: }
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract_or_throw< T >::type extract_or_throw(attribute_value const& value)
Chris@16: {
Chris@16:     value_extractor< T, fallback_to_throw > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(value));
Chris@16: }
Chris@16: 
Chris@16: template< typename T, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< T, DefaultT >::type extract_or_default(
Chris@16:     attribute_name const& name, attribute_value_set const& attrs, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< T, DefaultT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& > > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(name, attrs));
Chris@16: }
Chris@16: 
Chris@16: template< typename T, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< T, DefaultT >::type extract_or_default(
Chris@16:     attribute_name const& name, record const& rec, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< T, DefaultT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& > > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(name, rec));
Chris@16: }
Chris@16: 
Chris@16: template< typename T, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< T, DefaultT >::type extract_or_default(
Chris@16:     attribute_name const& name, record_view const& rec, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< T, DefaultT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& > > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(name, rec));
Chris@16: }
Chris@16: 
Chris@16: template< typename T, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< T, DefaultT >::type extract_or_default(attribute_value const& value, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< T, DefaultT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& > > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(value));
Chris@16: }
Chris@16: 
Chris@16: #endif // defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param keyword The keyword of the attribute value to extract.
Chris@16:  * \param attrs A set of attribute values in which to look for the specified attribute value.
Chris@16:  * \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT >
Chris@16: inline typename result_of::extract< typename DescriptorT::value_type, DescriptorT >::type
Chris@16: extract(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, attribute_value_set const& attrs)
Chris@16: {
Chris@16:     value_extractor< typename DescriptorT::value_type, fallback_to_none, DescriptorT > extractor;
Chris@16:     return extractor(keyword.get_name(), attrs);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param keyword The keyword of the attribute value to extract.
Chris@16:  * \param rec A log record. The attribute value will be sought among those associated with the record.
Chris@16:  * \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT >
Chris@16: inline typename result_of::extract< typename DescriptorT::value_type, DescriptorT >::type
Chris@16: extract(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record const& rec)
Chris@16: {
Chris@16:     value_extractor< typename DescriptorT::value_type, fallback_to_none, DescriptorT > extractor;
Chris@16:     return extractor(keyword.get_name(), rec);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param keyword The keyword of the attribute value to extract.
Chris@16:  * \param rec A log record view. The attribute value will be sought among those associated with the record.
Chris@16:  * \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT >
Chris@16: inline typename result_of::extract< typename DescriptorT::value_type, DescriptorT >::type
Chris@16: extract(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record_view const& rec)
Chris@16: {
Chris@16:     value_extractor< typename DescriptorT::value_type, fallback_to_none, DescriptorT > extractor;
Chris@16:     return extractor(keyword.get_name(), rec);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param keyword The keyword of the attribute value to extract.
Chris@16:  * \param attrs A set of attribute values in which to look for the specified attribute value.
Chris@16:  * \return The extracted value or a non-empty \c value_ref that refers to the value.
Chris@16:  * \throws An exception is thrown if the requested value cannot be extracted.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT >
Chris@16: inline typename result_of::extract_or_throw< typename DescriptorT::value_type, DescriptorT >::type
Chris@16: extract_or_throw(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, attribute_value_set const& attrs)
Chris@16: {
Chris@16:     value_extractor< typename DescriptorT::value_type, fallback_to_throw, DescriptorT > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(keyword.get_name(), attrs));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param keyword The keyword of the attribute value to extract.
Chris@16:  * \param rec A log record. The attribute value will be sought among those associated with the record.
Chris@16:  * \return The extracted value or a non-empty \c value_ref that refers to the value.
Chris@16:  * \throws An exception is thrown if the requested value cannot be extracted.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT >
Chris@16: inline typename result_of::extract_or_throw< typename DescriptorT::value_type, DescriptorT >::type
Chris@16: extract_or_throw(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record const& rec)
Chris@16: {
Chris@16:     value_extractor< typename DescriptorT::value_type, fallback_to_throw, DescriptorT > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(keyword.get_name(), rec));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \param keyword The keyword of the attribute value to extract.
Chris@16:  * \param rec A log record view. The attribute value will be sought among those associated with the record.
Chris@16:  * \return The extracted value or a non-empty \c value_ref that refers to the value.
Chris@16:  * \throws An exception is thrown if the requested value cannot be extracted.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT >
Chris@16: inline typename result_of::extract_or_throw< typename DescriptorT::value_type, DescriptorT >::type
Chris@16: extract_or_throw(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record_view const& rec)
Chris@16: {
Chris@16:     value_extractor< typename DescriptorT::value_type, fallback_to_throw, DescriptorT > extractor;
Chris@16:     return aux::unwrap_value_ref(extractor(keyword.get_name(), rec));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be extracted.
Chris@16:  *
Chris@16:  * \note Caution must be exercised if the default value is a temporary object. Because the function returns
Chris@16:  *       a reference, if the temporary object is destroyed, the reference may become dangling.
Chris@16:  *
Chris@16:  * \param keyword The keyword of the attribute value to extract.
Chris@16:  * \param attrs A set of attribute values in which to look for the specified attribute value.
Chris@16:  * \param def_val The default value
Chris@16:  * \return The extracted value, if found. The default value otherwise.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::type
Chris@16: extract_or_default(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, attribute_value_set const& attrs, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& >, DescriptorT > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(keyword.get_name(), attrs));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be visited.
Chris@16:  *
Chris@16:  * \note Caution must be exercised if the default value is a temporary object. Because the function returns
Chris@16:  *       a reference, if the temporary object is destroyed, the reference may become dangling.
Chris@16:  *
Chris@16:  * \param keyword The keyword of the attribute value to extract.
Chris@16:  * \param rec A log record. The attribute value will be sought among those associated with the record.
Chris@16:  * \param def_val The default value
Chris@16:  * \return The extracted value, if found. The default value otherwise.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::type
Chris@16: extract_or_default(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record const& rec, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& >, DescriptorT > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(keyword.get_name(), rec));
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function extracts an attribute value from the view. The user has to explicitly specify the
Chris@16:  * type or set of possible types of the attribute value to be visited.
Chris@16:  *
Chris@16:  * \note Caution must be exercised if the default value is a temporary object. Because the function returns
Chris@16:  *       a reference, if the temporary object is destroyed, the reference may become dangling.
Chris@16:  *
Chris@16:  * \param keyword The keyword of the attribute value to extract.
Chris@16:  * \param rec A log record view. The attribute value will be sought among those associated with the record.
Chris@16:  * \param def_val The default value
Chris@16:  * \return The extracted value, if found. The default value otherwise.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::type
Chris@16: extract_or_default(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record_view const& rec, DefaultT const& def_val)
Chris@16: {
Chris@16:     typedef typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::extracted_type extracted_type;
Chris@16:     value_extractor< extracted_type, fallback_to_default< DefaultT const& >, DescriptorT > extractor(def_val);
Chris@16:     return aux::unwrap_value_ref(extractor(keyword.get_name(), rec));
Chris@16: }
Chris@16: 
Chris@16: #if !defined(BOOST_LOG_DOXYGEN_PASS)
Chris@16: 
Chris@16: template< typename T, typename TagT >
Chris@16: inline typename result_of::extract< T, TagT >::type attribute_value::extract() const
Chris@16: {
Chris@16:     return boost::log::extract< T, TagT >(*this);
Chris@16: }
Chris@16: 
Chris@16: template< typename T, typename TagT >
Chris@16: inline typename result_of::extract_or_throw< T, TagT >::type attribute_value::extract_or_throw() const
Chris@16: {
Chris@16:     return boost::log::extract_or_throw< T, TagT >(*this);
Chris@16: }
Chris@16: 
Chris@16: template< typename T, typename TagT >
Chris@16: inline typename result_of::extract_or_default< T, T, TagT >::type attribute_value::extract_or_default(T const& def_value) const
Chris@16: {
Chris@16:     return boost::log::extract_or_default< T, TagT >(*this, def_value);
Chris@16: }
Chris@16: 
Chris@16: template< typename T, typename TagT, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< T, DefaultT, TagT >::type attribute_value::extract_or_default(DefaultT const& def_value) const
Chris@16: {
Chris@16:     return boost::log::extract_or_default< T, TagT >(*this, def_value);
Chris@16: }
Chris@16: 
Chris@16: #if defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract< T >::type attribute_value::extract() const
Chris@16: {
Chris@16:     return boost::log::extract< T >(*this);
Chris@16: }
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract_or_throw< T >::type attribute_value::extract_or_throw() const
Chris@16: {
Chris@16:     return boost::log::extract_or_throw< T >(*this);
Chris@16: }
Chris@16: 
Chris@16: template< typename T >
Chris@16: inline typename result_of::extract_or_default< T, T >::type attribute_value::extract_or_default(T const& def_value) const
Chris@16: {
Chris@16:     return boost::log::extract_or_default< T >(*this, def_value);
Chris@16: }
Chris@16: 
Chris@16: template< typename T, typename DefaultT >
Chris@16: inline typename result_of::extract_or_default< T, DefaultT >::type attribute_value::extract_or_default(DefaultT const& def_value) const
Chris@16: {
Chris@16:     return boost::log::extract_or_default< T >(*this, def_value);
Chris@16: }
Chris@16: 
Chris@16: #endif // defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
Chris@16: 
Chris@16: #endif // !defined(BOOST_LOG_DOXYGEN_PASS)
Chris@16: 
Chris@16: #undef BOOST_LOG_AUX_VOID_DEFAULT
Chris@16: 
Chris@16: BOOST_LOG_CLOSE_NAMESPACE // namespace log
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/log/detail/footer.hpp>
Chris@16: 
Chris@16: #endif // BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_HPP_INCLUDED_