| /* |
| * Copyright Andrey Semashev 2007 - 2015. |
| * Distributed under the Boost Software License, Version 1.0. |
| * (See accompanying file LICENSE_1_0.txt or copy at |
| * http://www.boost.org/LICENSE_1_0.txt) |
| */ |
| /*! |
| * \file value_visitation.hpp |
| * \author Andrey Semashev |
| * \date 01.03.2008 |
| * |
| * The header contains implementation of convenience tools to apply visitors to an attribute value |
| * in the view. |
| */ |
| |
| #ifndef BOOST_LOG_ATTRIBUTES_VALUE_VISITATION_HPP_INCLUDED_ |
| #define BOOST_LOG_ATTRIBUTES_VALUE_VISITATION_HPP_INCLUDED_ |
| |
| #include <boost/log/detail/config.hpp> |
| #include <boost/log/exceptions.hpp> |
| #include <boost/log/core/record.hpp> |
| #include <boost/log/attributes/attribute_name.hpp> |
| #include <boost/log/attributes/attribute_value.hpp> |
| #include <boost/log/attributes/attribute.hpp> |
| #include <boost/log/attributes/attribute_value_set.hpp> |
| #include <boost/log/attributes/value_visitation_fwd.hpp> |
| #include <boost/log/attributes/fallback_policy.hpp> |
| #include <boost/log/expressions/keyword_fwd.hpp> |
| #include <boost/utility/explicit_operator_bool.hpp> |
| #include <boost/log/utility/type_dispatch/static_type_dispatcher.hpp> |
| #include <boost/log/detail/header.hpp> |
| |
| #ifdef BOOST_HAS_PRAGMA_ONCE |
| #pragma once |
| #endif |
| |
| namespace boost { |
| |
| BOOST_LOG_OPEN_NAMESPACE |
| |
| /*! |
| * \brief The class represents attribute value visitation result |
| * |
| * The main purpose of this class is to provide a convenient interface for checking |
| * whether the attribute value visitation succeeded or not. It also allows to discover |
| * the actual cause of failure, should the operation fail. |
| */ |
| class visitation_result |
| { |
| public: |
| //! Error codes for attribute value visitation |
| enum error_code |
| { |
| ok, //!< The attribute value has been visited successfully |
| value_not_found, //!< The attribute value is not present in the view |
| value_has_invalid_type //!< The attribute value is present in the view, but has an unexpected type |
| }; |
| |
| private: |
| error_code m_code; |
| |
| public: |
| /*! |
| * Initializing constructor. Creates the result that is equivalent to the |
| * specified error code. |
| */ |
| BOOST_CONSTEXPR visitation_result(error_code code = ok) BOOST_NOEXCEPT : m_code(code) {} |
| |
| /*! |
| * Checks if the visitation was successful. |
| * |
| * \return \c true if the value was visited successfully, \c false otherwise. |
| */ |
| BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT() |
| /*! |
| * Checks if the visitation was unsuccessful. |
| * |
| * \return \c false if the value was visited successfully, \c true otherwise. |
| */ |
| bool operator! () const BOOST_NOEXCEPT { return (m_code != ok); } |
| |
| /*! |
| * \return The actual result code of value visitation |
| */ |
| error_code code() const BOOST_NOEXCEPT { return m_code; } |
| }; |
| |
| /*! |
| * \brief Generic attribute value visitor invoker |
| * |
| * Attribute value invoker is a functional object that attempts to find and extract the stored |
| * attribute value from the attribute value view or a log record. The extracted value is passed to |
| * a unary function object (the visitor) provided by user. |
| * |
| * The invoker can be specialized on one or several attribute value types that should be |
| * specified in the second template argument. |
| */ |
| template< typename T, typename FallbackPolicyT > |
| class value_visitor_invoker : |
| private FallbackPolicyT |
| { |
| typedef value_visitor_invoker< T, FallbackPolicyT > this_type; |
| |
| public: |
| //! Attribute value types |
| typedef T value_type; |
| |
| //! Fallback policy |
| typedef FallbackPolicyT fallback_policy; |
| |
| //! Function object result type |
| typedef visitation_result result_type; |
| |
| public: |
| /*! |
| * Default constructor |
| */ |
| BOOST_DEFAULTED_FUNCTION(value_visitor_invoker(), {}) |
| |
| /*! |
| * Copy constructor |
| */ |
| value_visitor_invoker(value_visitor_invoker const& that) : fallback_policy(static_cast< fallback_policy const& >(that)) |
| { |
| } |
| |
| /*! |
| * Initializing constructor |
| * |
| * \param arg Fallback policy argument |
| */ |
| template< typename U > |
| explicit value_visitor_invoker(U const& arg) : fallback_policy(arg) {} |
| |
| /*! |
| * Visitation operator. Attempts to acquire the stored value of one of the supported types. If acquisition succeeds, |
| * the value is passed to \a visitor. |
| * |
| * \param attr An attribute value to apply the visitor to. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename VisitorT > |
| result_type operator() (attribute_value const& attr, VisitorT visitor) const |
| { |
| if (!!attr) |
| { |
| static_type_dispatcher< value_type > disp(visitor); |
| if (attr.dispatch(disp) || fallback_policy::apply_default(visitor)) |
| { |
| return visitation_result::ok; |
| } |
| else |
| { |
| fallback_policy::on_invalid_type(attr.get_type()); |
| return visitation_result::value_has_invalid_type; |
| } |
| } |
| |
| if (fallback_policy::apply_default(visitor)) |
| return visitation_result::ok; |
| |
| fallback_policy::on_missing_value(); |
| return visitation_result::value_not_found; |
| } |
| |
| /*! |
| * Visitation operator. Looks for an attribute value with the specified name |
| * and tries to acquire the stored value of one of the supported types. If acquisition succeeds, |
| * the value is passed to \a visitor. |
| * |
| * \param name Attribute value name. |
| * \param attrs A set of attribute values in which to look for the specified attribute value. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename VisitorT > |
| result_type operator() (attribute_name const& name, attribute_value_set const& attrs, VisitorT visitor) const |
| { |
| try |
| { |
| attribute_value_set::const_iterator it = attrs.find(name); |
| if (it != attrs.end()) |
| return operator() (it->second, visitor); |
| else |
| return operator() (attribute_value(), visitor); |
| } |
| catch (exception& e) |
| { |
| // Attach the attribute name to the exception |
| boost::log::aux::attach_attribute_name_info(e, name); |
| throw; |
| } |
| } |
| |
| /*! |
| * Visitation operator. Looks for an attribute value with the specified name |
| * and tries to acquire the stored value of one of the supported types. If acquisition succeeds, |
| * the value is passed to \a visitor. |
| * |
| * \param name Attribute value name. |
| * \param rec A log record. The attribute value will be sought among those associated with the record. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename VisitorT > |
| result_type operator() (attribute_name const& name, record const& rec, VisitorT visitor) const |
| { |
| return operator() (name, rec.attribute_values(), visitor); |
| } |
| |
| /*! |
| * Visitation operator. Looks for an attribute value with the specified name |
| * and tries to acquire the stored value of one of the supported types. If acquisition succeeds, |
| * the value is passed to \a visitor. |
| * |
| * \param name Attribute value name. |
| * \param rec A log record view. The attribute value will be sought among those associated with the record. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename VisitorT > |
| result_type operator() (attribute_name const& name, record_view const& rec, VisitorT visitor) const |
| { |
| return operator() (name, rec.attribute_values(), visitor); |
| } |
| |
| /*! |
| * \returns Fallback policy |
| */ |
| fallback_policy const& get_fallback_policy() const |
| { |
| return *static_cast< fallback_policy const* >(this); |
| } |
| }; |
| |
| /*! |
| * The function applies a visitor to an attribute value from the view. The user has to explicitly specify the |
| * type or set of possible types of the attribute value to be visited. |
| * |
| * \param name The name of the attribute value to visit. |
| * \param attrs A set of attribute values in which to look for the specified attribute value. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename T, typename VisitorT > |
| inline visitation_result |
| visit(attribute_name const& name, attribute_value_set const& attrs, VisitorT visitor) |
| { |
| value_visitor_invoker< T > invoker; |
| return invoker(name, attrs, visitor); |
| } |
| |
| /*! |
| * The function applies a visitor to an attribute value from the view. The user has to explicitly specify the |
| * type or set of possible types of the attribute value to be visited. |
| * |
| * \param name The name of the attribute value to visit. |
| * \param rec A log record. The attribute value will be sought among those associated with the record. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename T, typename VisitorT > |
| inline visitation_result |
| visit(attribute_name const& name, record const& rec, VisitorT visitor) |
| { |
| value_visitor_invoker< T > invoker; |
| return invoker(name, rec, visitor); |
| } |
| |
| /*! |
| * The function applies a visitor to an attribute value from the view. The user has to explicitly specify the |
| * type or set of possible types of the attribute value to be visited. |
| * |
| * \param name The name of the attribute value to visit. |
| * \param rec A log record view. The attribute value will be sought among those associated with the record. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename T, typename VisitorT > |
| inline visitation_result |
| visit(attribute_name const& name, record_view const& rec, VisitorT visitor) |
| { |
| value_visitor_invoker< T > invoker; |
| return invoker(name, rec, visitor); |
| } |
| |
| /*! |
| * The function applies a visitor to an attribute value. The user has to explicitly specify the |
| * type or set of possible types of the attribute value to be visited. |
| * |
| * \param value The attribute value to visit. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename T, typename VisitorT > |
| inline visitation_result |
| visit(attribute_value const& value, VisitorT visitor) |
| { |
| value_visitor_invoker< T > invoker; |
| return invoker(value, visitor); |
| } |
| |
| /*! |
| * The function applies a visitor to an attribute value from the view. The user has to explicitly specify the |
| * type or set of possible types of the attribute value to be visited. |
| * |
| * \param keyword The keyword of the attribute value to visit. |
| * \param attrs A set of attribute values in which to look for the specified attribute value. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename DescriptorT, template< typename > class ActorT, typename VisitorT > |
| inline visitation_result |
| visit(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, attribute_value_set const& attrs, VisitorT visitor) |
| { |
| value_visitor_invoker< typename DescriptorT::value_type > invoker; |
| return invoker(keyword.get_name(), attrs, visitor); |
| } |
| |
| /*! |
| * The function applies a visitor to an attribute value from the view. The user has to explicitly specify the |
| * type or set of possible types of the attribute value to be visited. |
| * |
| * \param keyword The keyword of the attribute value to visit. |
| * \param rec A log record. The attribute value will be sought among those associated with the record. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename DescriptorT, template< typename > class ActorT, typename VisitorT > |
| inline visitation_result |
| visit(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record const& rec, VisitorT visitor) |
| { |
| value_visitor_invoker< typename DescriptorT::value_type > invoker; |
| return invoker(keyword.get_name(), rec, visitor); |
| } |
| |
| /*! |
| * The function applies a visitor to an attribute value from the view. The user has to explicitly specify the |
| * type or set of possible types of the attribute value to be visited. |
| * |
| * \param keyword The keyword of the attribute value to visit. |
| * \param rec A log record view. The attribute value will be sought among those associated with the record. |
| * \param visitor A receiving function object to pass the attribute value to. |
| * \return The result of visitation. |
| */ |
| template< typename DescriptorT, template< typename > class ActorT, typename VisitorT > |
| inline visitation_result |
| visit(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record_view const& rec, VisitorT visitor) |
| { |
| value_visitor_invoker< typename DescriptorT::value_type > invoker; |
| return invoker(keyword.get_name(), rec, visitor); |
| } |
| |
| |
| #if !defined(BOOST_LOG_DOXYGEN_PASS) |
| |
| template< typename T, typename VisitorT > |
| inline visitation_result attribute_value::visit(VisitorT visitor) const |
| { |
| return boost::log::visit< T >(*this, visitor); |
| } |
| |
| #endif // !defined(BOOST_LOG_DOXYGEN_PASS) |
| |
| BOOST_LOG_CLOSE_NAMESPACE // namespace log |
| |
| } // namespace boost |
| |
| #include <boost/log/detail/footer.hpp> |
| |
| #endif // BOOST_LOG_ATTRIBUTES_VALUE_VISITATION_HPP_INCLUDED_ |