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_visitation.hpp
Chris@16:  * \author Andrey Semashev
Chris@16:  * \date   01.03.2008
Chris@16:  *
Chris@16:  * The header contains implementation of convenience tools to apply visitors to an attribute value
Chris@16:  * in the view.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_LOG_ATTRIBUTES_VALUE_VISITATION_HPP_INCLUDED_
Chris@16: #define BOOST_LOG_ATTRIBUTES_VALUE_VISITATION_HPP_INCLUDED_
Chris@16: 
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_visitation_fwd.hpp>
Chris@16: #include <boost/log/attributes/fallback_policy.hpp>
Chris@16: #include <boost/log/expressions/keyword_fwd.hpp>
Chris@16: #include <boost/utility/explicit_operator_bool.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: /*!
Chris@16:  * \brief The class represents attribute value visitation result
Chris@16:  *
Chris@16:  * The main purpose of this class is to provide a convenient interface for checking
Chris@16:  * whether the attribute value visitation succeeded or not. It also allows to discover
Chris@16:  * the actual cause of failure, should the operation fail.
Chris@16:  */
Chris@16: class visitation_result
Chris@16: {
Chris@16: public:
Chris@16:     //! Error codes for attribute value visitation
Chris@16:     enum error_code
Chris@16:     {
Chris@16:         ok,                     //!< The attribute value has been visited successfully
Chris@16:         value_not_found,        //!< The attribute value is not present in the view
Chris@16:         value_has_invalid_type  //!< The attribute value is present in the view, but has an unexpected type
Chris@16:     };
Chris@16: 
Chris@16: private:
Chris@16:     error_code m_code;
Chris@16: 
Chris@16: public:
Chris@16:     /*!
Chris@16:      * Initializing constructor. Creates the result that is equivalent to the
Chris@16:      * specified error code.
Chris@16:      */
Chris@16:     BOOST_CONSTEXPR visitation_result(error_code code = ok) BOOST_NOEXCEPT : m_code(code) {}
Chris@16: 
Chris@16:     /*!
Chris@16:      * Checks if the visitation was successful.
Chris@16:      *
Chris@16:      * \return \c true if the value was visited successfully, \c false otherwise.
Chris@16:      */
Chris@101:     BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
Chris@16:     /*!
Chris@16:      * Checks if the visitation was unsuccessful.
Chris@16:      *
Chris@16:      * \return \c false if the value was visited successfully, \c true otherwise.
Chris@16:      */
Chris@16:     bool operator! () const BOOST_NOEXCEPT { return (m_code != ok); }
Chris@16: 
Chris@16:     /*!
Chris@16:      * \return The actual result code of value visitation
Chris@16:      */
Chris@16:     error_code code() const BOOST_NOEXCEPT { return m_code; }
Chris@16: };
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief Generic attribute value visitor invoker
Chris@16:  *
Chris@16:  * Attribute value invoker is a functional object that attempts to find and extract the stored
Chris@16:  * attribute value from the attribute value view or a log record. The extracted value is passed to
Chris@16:  * a unary function object (the visitor) provided by user.
Chris@16:  *
Chris@16:  * The invoker can be specialized on one or several attribute value types that should be
Chris@16:  * specified in the second template argument.
Chris@16:  */
Chris@16: template< typename T, typename FallbackPolicyT >
Chris@16: class value_visitor_invoker :
Chris@16:     private FallbackPolicyT
Chris@16: {
Chris@16:     typedef value_visitor_invoker< T, FallbackPolicyT > this_type;
Chris@16: 
Chris@16: public:
Chris@16:     //! Attribute value types
Chris@16:     typedef T value_type;
Chris@16: 
Chris@16:     //! Fallback policy
Chris@16:     typedef FallbackPolicyT fallback_policy;
Chris@16: 
Chris@16:     //! Function object result type
Chris@16:     typedef visitation_result result_type;
Chris@16: 
Chris@16: public:
Chris@16:     /*!
Chris@16:      * Default constructor
Chris@16:      */
Chris@16:     BOOST_DEFAULTED_FUNCTION(value_visitor_invoker(), {})
Chris@16: 
Chris@16:     /*!
Chris@16:      * Copy constructor
Chris@16:      */
Chris@16:     value_visitor_invoker(value_visitor_invoker const& that) : fallback_policy(static_cast< fallback_policy const& >(that))
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * Initializing constructor
Chris@16:      *
Chris@16:      * \param arg Fallback policy argument
Chris@16:      */
Chris@16:     template< typename U >
Chris@16:     explicit value_visitor_invoker(U const& arg) : fallback_policy(arg) {}
Chris@16: 
Chris@16:     /*!
Chris@16:      * Visitation operator. Attempts to acquire the stored value of one of the supported types. If acquisition succeeds,
Chris@16:      * the value is passed to \a visitor.
Chris@16:      *
Chris@16:      * \param attr An attribute value to apply the visitor to.
Chris@16:      * \param visitor A receiving function object to pass the attribute value to.
Chris@16:      * \return The result of visitation.
Chris@16:      */
Chris@16:     template< typename VisitorT >
Chris@16:     result_type operator() (attribute_value const& attr, VisitorT visitor) const
Chris@16:     {
Chris@16:         if (!!attr)
Chris@16:         {
Chris@16:             static_type_dispatcher< value_type > disp(visitor);
Chris@16:             if (attr.dispatch(disp) || fallback_policy::apply_default(visitor))
Chris@16:             {
Chris@16:                 return visitation_result::ok;
Chris@16:             }
Chris@16:             else
Chris@16:             {
Chris@16:                 fallback_policy::on_invalid_type(attr.get_type());
Chris@16:                 return visitation_result::value_has_invalid_type;
Chris@16:             }
Chris@16:         }
Chris@16: 
Chris@16:         if (fallback_policy::apply_default(visitor))
Chris@16:             return visitation_result::ok;
Chris@16: 
Chris@16:         fallback_policy::on_missing_value();
Chris@16:         return visitation_result::value_not_found;
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * Visitation 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 acquisition succeeds,
Chris@16:      * the value is passed to \a visitor.
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:      * \param visitor A receiving function object to pass the attribute value to.
Chris@16:      * \return The result of visitation.
Chris@16:      */
Chris@16:     template< typename VisitorT >
Chris@16:     result_type operator() (attribute_name const& name, attribute_value_set const& attrs, VisitorT visitor) 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, visitor);
Chris@16:             else
Chris@16:                 return operator() (attribute_value(), visitor);
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:      * Visitation 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 acquisition succeeds,
Chris@16:      * the value is passed to \a visitor.
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:      * \param visitor A receiving function object to pass the attribute value to.
Chris@16:      * \return The result of visitation.
Chris@16:      */
Chris@16:     template< typename VisitorT >
Chris@16:     result_type operator() (attribute_name const& name, record const& rec, VisitorT visitor) const
Chris@16:     {
Chris@16:         return operator() (name, rec.attribute_values(), visitor);
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * Visitation 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 acquisition succeeds,
Chris@16:      * the value is passed to \a visitor.
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:      * \param visitor A receiving function object to pass the attribute value to.
Chris@16:      * \return The result of visitation.
Chris@16:      */
Chris@16:     template< typename VisitorT >
Chris@16:     result_type operator() (attribute_name const& name, record_view const& rec, VisitorT visitor) const
Chris@16:     {
Chris@16:         return operator() (name, rec.attribute_values(), visitor);
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: /*!
Chris@16:  * The function applies a visitor to 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:  * \param name The name of the attribute value to visit.
Chris@16:  * \param attrs A set of attribute values in which to look for the specified attribute value.
Chris@16:  * \param visitor A receiving function object to pass the attribute value to.
Chris@16:  * \return The result of visitation.
Chris@16:  */
Chris@16: template< typename T, typename VisitorT >
Chris@16: inline visitation_result
Chris@16: visit(attribute_name const& name, attribute_value_set const& attrs, VisitorT visitor)
Chris@16: {
Chris@16:     value_visitor_invoker< T > invoker;
Chris@16:     return invoker(name, attrs, visitor);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function applies a visitor to 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:  * \param name The name of the attribute value to visit.
Chris@16:  * \param rec A log record. The attribute value will be sought among those associated with the record.
Chris@16:  * \param visitor A receiving function object to pass the attribute value to.
Chris@16:  * \return The result of visitation.
Chris@16:  */
Chris@16: template< typename T, typename VisitorT >
Chris@16: inline visitation_result
Chris@16: visit(attribute_name const& name, record const& rec, VisitorT visitor)
Chris@16: {
Chris@16:     value_visitor_invoker< T > invoker;
Chris@16:     return invoker(name, rec, visitor);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function applies a visitor to 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:  * \param name The name of the attribute value to visit.
Chris@16:  * \param rec A log record view. The attribute value will be sought among those associated with the record.
Chris@16:  * \param visitor A receiving function object to pass the attribute value to.
Chris@16:  * \return The result of visitation.
Chris@16:  */
Chris@16: template< typename T, typename VisitorT >
Chris@16: inline visitation_result
Chris@16: visit(attribute_name const& name, record_view const& rec, VisitorT visitor)
Chris@16: {
Chris@16:     value_visitor_invoker< T > invoker;
Chris@16:     return invoker(name, rec, visitor);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function applies a visitor to an attribute value. 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:  * \param value The attribute value to visit.
Chris@16:  * \param visitor A receiving function object to pass the attribute value to.
Chris@16:  * \return The result of visitation.
Chris@16:  */
Chris@16: template< typename T, typename VisitorT >
Chris@16: inline visitation_result
Chris@16: visit(attribute_value const& value, VisitorT visitor)
Chris@16: {
Chris@16:     value_visitor_invoker< T > invoker;
Chris@16:     return invoker(value, visitor);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function applies a visitor to 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:  * \param keyword The keyword of the attribute value to visit.
Chris@16:  * \param attrs A set of attribute values in which to look for the specified attribute value.
Chris@16:  * \param visitor A receiving function object to pass the attribute value to.
Chris@16:  * \return The result of visitation.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT, typename VisitorT >
Chris@16: inline visitation_result
Chris@16: visit(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, attribute_value_set const& attrs, VisitorT visitor)
Chris@16: {
Chris@16:     value_visitor_invoker< typename DescriptorT::value_type > invoker;
Chris@16:     return invoker(keyword.get_name(), attrs, visitor);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function applies a visitor to 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:  * \param keyword The keyword of the attribute value to visit.
Chris@16:  * \param rec A log record. The attribute value will be sought among those associated with the record.
Chris@16:  * \param visitor A receiving function object to pass the attribute value to.
Chris@16:  * \return The result of visitation.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT, typename VisitorT >
Chris@16: inline visitation_result
Chris@16: visit(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record const& rec, VisitorT visitor)
Chris@16: {
Chris@16:     value_visitor_invoker< typename DescriptorT::value_type > invoker;
Chris@16:     return invoker(keyword.get_name(), rec, visitor);
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16:  * The function applies a visitor to 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:  * \param keyword The keyword of the attribute value to visit.
Chris@16:  * \param rec A log record view. The attribute value will be sought among those associated with the record.
Chris@16:  * \param visitor A receiving function object to pass the attribute value to.
Chris@16:  * \return The result of visitation.
Chris@16:  */
Chris@16: template< typename DescriptorT, template< typename > class ActorT, typename VisitorT >
Chris@16: inline visitation_result
Chris@16: visit(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record_view const& rec, VisitorT visitor)
Chris@16: {
Chris@16:     value_visitor_invoker< typename DescriptorT::value_type > invoker;
Chris@16:     return invoker(keyword.get_name(), rec, visitor);
Chris@16: }
Chris@16: 
Chris@16: 
Chris@16: #if !defined(BOOST_LOG_DOXYGEN_PASS)
Chris@16: 
Chris@16: template< typename T, typename VisitorT >
Chris@16: inline visitation_result attribute_value::visit(VisitorT visitor) const
Chris@16: {
Chris@16:     return boost::log::visit< T >(*this, visitor);
Chris@16: }
Chris@16: 
Chris@16: #endif // !defined(BOOST_LOG_DOXYGEN_PASS)
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_VISITATION_HPP_INCLUDED_