sl@0: //  (C) Copyright Jeremy Siek 2004 
sl@0: //  Distributed under the Boost Software License, Version 1.0. (See
sl@0: //  accompanying file LICENSE_1_0.txt or copy at
sl@0: //  http://www.boost.org/LICENSE_1_0.txt)
sl@0: 
sl@0: #ifndef BOOST_DETAIL_PROPERTY_HPP
sl@0: #define BOOST_DETAIL_PROPERTY_HPP
sl@0: 
sl@0: #include <utility> // for std::pair
sl@0: #include <boost/type_traits/same_traits.hpp> // for is_same
sl@0: 
sl@0: namespace boost {
sl@0: 
sl@0:   namespace detail {
sl@0: 
sl@0:     template <class PropertyTag1, class PropertyTag2>
sl@0:     struct same_property {
sl@0:       enum { value = is_same<PropertyTag1,PropertyTag2>::value };
sl@0:     };
sl@0: 
sl@0:     struct error_property_not_found { };
sl@0: 
sl@0:     template <int TagMatched>
sl@0:     struct property_value_dispatch {
sl@0:       template <class PropertyTag, class T, class Tag>
sl@0:       inline static T& get_value(PropertyTag& p, T*, Tag) {
sl@0:         return p.m_value; 
sl@0:       }
sl@0:       template <class PropertyTag, class T, class Tag>
sl@0:       inline static const T& const_get_value(const PropertyTag& p, T*, Tag) {
sl@0:         return p.m_value; 
sl@0:       }
sl@0:     };
sl@0: 
sl@0:     template <class PropertyList>
sl@0:     struct property_value_end {
sl@0:       template <class T> struct result { typedef T type; };
sl@0: 
sl@0:       template <class T, class Tag>
sl@0:       inline static T& get_value(PropertyList& p, T* t, Tag tag) {
sl@0:         typedef typename PropertyList::next_type Next;
sl@0:         typedef typename Next::tag_type Next_tag;
sl@0:         enum { match = same_property<Next_tag,Tag>::value };
sl@0:         return property_value_dispatch<match>
sl@0:           ::get_value(static_cast<Next&>(p), t, tag);
sl@0:       }
sl@0:       template <class T, class Tag>
sl@0:       inline static const T& const_get_value(const PropertyList& p, T* t, Tag tag) {
sl@0:         typedef typename PropertyList::next_type Next;
sl@0:         typedef typename Next::tag_type Next_tag;
sl@0:         enum { match = same_property<Next_tag,Tag>::value };
sl@0:         return property_value_dispatch<match>
sl@0:           ::const_get_value(static_cast<const Next&>(p), t, tag);
sl@0:       }
sl@0:     };
sl@0:     template <>
sl@0:     struct property_value_end<no_property> {
sl@0:       template <class T> struct result { 
sl@0:         typedef detail::error_property_not_found type; 
sl@0:       };
sl@0: 
sl@0:       // Stop the recursion and return error
sl@0:       template <class T, class Tag>
sl@0:       inline static detail::error_property_not_found&
sl@0:       get_value(no_property&, T*, Tag) {
sl@0:         static error_property_not_found s_prop_not_found;
sl@0:         return s_prop_not_found;
sl@0:       }
sl@0:       template <class T, class Tag>
sl@0:       inline static const detail::error_property_not_found&
sl@0:       const_get_value(const no_property&, T*, Tag) {
sl@0:         static error_property_not_found s_prop_not_found;
sl@0:         return s_prop_not_found;
sl@0:       }
sl@0:     };
sl@0: 
sl@0:     template <>
sl@0:     struct property_value_dispatch<0> {
sl@0:       template <class PropertyList, class T, class Tag>
sl@0:       inline static typename property_value_end<PropertyList>::template result<T>::type&
sl@0:       get_value(PropertyList& p, T* t, Tag tag) {
sl@0:         return property_value_end<PropertyList>::get_value(p, t, tag);
sl@0:       }
sl@0:       template <class PropertyList, class T, class Tag>
sl@0:       inline static const typename property_value_end<PropertyList>::template result<T>::type&
sl@0:       const_get_value(const PropertyList& p, T* t, Tag tag) {
sl@0:         return property_value_end<PropertyList>::const_get_value(p, t, tag);
sl@0:       }
sl@0:     };
sl@0: 
sl@0:     template <class PropertyList>
sl@0:     struct build_property_tag_value_alist
sl@0:     {
sl@0:       typedef typename PropertyList::next_type NextProperty;
sl@0:       typedef typename PropertyList::value_type Value;
sl@0:       typedef typename PropertyList::tag_type Tag;
sl@0:       typedef typename build_property_tag_value_alist<NextProperty>::type Next;
sl@0:       typedef std::pair< std::pair<Tag,Value>, Next> type;
sl@0:     };
sl@0:     template <>
sl@0:     struct build_property_tag_value_alist<no_property>
sl@0:     {
sl@0:       typedef no_property type;
sl@0:     };
sl@0: 
sl@0: #if !defined BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
sl@0:     template <class TagValueAList, class Tag>
sl@0:     struct extract_value {
sl@0:       typedef error_property_not_found type;
sl@0:     };
sl@0:     template <class Value, class Tag1, class Tag2, class Rest>
sl@0:     struct extract_value< std::pair<std::pair<Tag1,Value>,Rest>, Tag2> {
sl@0:       typedef typename extract_value<Rest,Tag2>::type type;
sl@0:     };
sl@0:     template <class Value, class Tag, class Rest>
sl@0:     struct extract_value< std::pair<std::pair<Tag,Value>,Rest>, Tag> {
sl@0:       typedef Value type;
sl@0:     };
sl@0: #else
sl@0:     // VC++ workaround:
sl@0:     // The main idea here is to replace partial specialization with
sl@0:     // nested template member classes. Of course there is the
sl@0:     // further complication that the outer class of the nested
sl@0:     // template class cannot itself be a template class.
sl@0:     // Hence the need for the ev_selector. -JGS
sl@0: 
sl@0:     struct recursive_extract;
sl@0:     struct end_extract;
sl@0: 
sl@0:     template <class TagValueAList>
sl@0:     struct ev_selector { typedef recursive_extract type; };
sl@0:     template <>
sl@0:     struct ev_selector<no_property> { typedef end_extract type; };
sl@0: 
sl@0:     struct recursive_extract {
sl@0:       template <class TagValueAList, class Tag1>
sl@0:       struct bind_ {
sl@0:         typedef typename TagValueAList::first_type AListFirst;
sl@0:         typedef typename AListFirst::first_type Tag2;
sl@0:         typedef typename AListFirst::second_type Value;
sl@0:         enum { match = same_property<Tag1,Tag2>::value };
sl@0:         typedef typename TagValueAList::second_type Next;
sl@0:         typedef typename ev_selector<Next>::type Extractor;
sl@0:         typedef typename boost::ct_if< match, Value, 
sl@0:           typename Extractor::template bind_<Next,Tag1>::type
sl@0:         >::type type;
sl@0:       };
sl@0:     };
sl@0:     struct end_extract {
sl@0:       template <class AList, class Tag1>
sl@0:       struct bind_ {
sl@0:         typedef error_property_not_found type;
sl@0:       };
sl@0:     };
sl@0: #endif //!defined BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
sl@0: 
sl@0:   } // namespace detail 
sl@0: } // namespace boost
sl@0: 
sl@0: #endif // BOOST_DETAIL_PROPERTY_HPP