Chris@16: //  Copyright (c) 2001-2011 Hartmut Kaiser
Chris@16: //
Chris@16: //  Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@16: //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #if !defined(BOOST_SPIRIT_KARMA_EXTRACT_FROM_SEP_30_2009_0732AM)
Chris@16: #define BOOST_SPIRIT_KARMA_EXTRACT_FROM_SEP_30_2009_0732AM
Chris@16: 
Chris@16: #if defined(_MSC_VER)
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/spirit/include/phoenix_core.hpp>
Chris@16: #include <boost/spirit/home/support/unused.hpp>
Chris@16: #include <boost/spirit/home/support/attributes_fwd.hpp>
Chris@16: #include <boost/spirit/home/karma/detail/attributes.hpp>
Chris@16: #include <boost/spirit/home/support/container.hpp>
Chris@16: 
Chris@16: #include <boost/ref.hpp>
Chris@16: #include <boost/optional.hpp>
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: namespace boost { namespace spirit { namespace traits
Chris@16: {
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     //  This file contains attribute extraction utilities. The utilities
Chris@16:     //  provided also accept spirit's unused_type; all no-ops. Compiler
Chris@16:     //  optimization will easily strip these away.
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16: 
Chris@16:     namespace detail
Chris@16:     {
Chris@16:         ///////////////////////////////////////////////////////////////////////
Chris@16:         // extract first and second element of a fusion sequence
Chris@16:         template <typename T>
Chris@16:         struct add_const_ref
Chris@16:           : add_reference<typename add_const<T>::type>
Chris@16:         {};
Chris@16: 
Chris@16:         template <typename T, int N>
Chris@16:         struct value_at_c
Chris@16:           : add_const_ref<typename fusion::result_of::value_at_c<T, N>::type>
Chris@16:         {};
Chris@16:     }
Chris@16: 
Chris@16:     // This is the default case: the plain attribute values
Chris@16:     template <typename Attribute, typename Exposed, typename Enable/*= void*/>
Chris@16:     struct extract_from_attribute
Chris@16:     {
Chris@16:         typedef typename traits::one_element_sequence<Attribute>::type
Chris@16:             is_one_element_sequence;
Chris@16: 
Chris@16:         typedef typename mpl::eval_if<
Chris@16:             is_one_element_sequence
Chris@16:           , detail::value_at_c<Attribute, 0>
Chris@16:           , mpl::identity<Attribute const&>
Chris@16:         >::type type;
Chris@16: 
Chris@16:         template <typename Context>
Chris@16:         static type call(Attribute const& attr, Context&, mpl::false_)
Chris@16:         {
Chris@16:             return attr;
Chris@16:         }
Chris@16: 
Chris@16:         // This handles the case where the attribute is a single element fusion
Chris@16:         // sequence. We silently extract the only element and treat it as the
Chris@16:         // attribute to generate output from.
Chris@16:         template <typename Context>
Chris@16:         static type call(Attribute const& attr, Context& ctx, mpl::true_)
Chris@16:         {
Chris@16:             return extract_from<Exposed>(fusion::at_c<0>(attr), ctx);
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Context>
Chris@16:         static type call(Attribute const& attr, Context& ctx)
Chris@16:         {
Chris@16:             return call(attr, ctx, is_one_element_sequence());
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     // This handles optional attributes.
Chris@16:     template <typename Attribute, typename Exposed>
Chris@16:     struct extract_from_attribute<boost::optional<Attribute>, Exposed>
Chris@16:     {
Chris@16:         typedef Attribute const& type;
Chris@16: 
Chris@16:         template <typename Context>
Chris@16:         static type call(boost::optional<Attribute> const& attr, Context& ctx)
Chris@16:         {
Chris@16:             return extract_from<Exposed>(boost::get<Attribute>(attr), ctx);
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     template <typename Attribute, typename Exposed>
Chris@16:     struct extract_from_attribute<boost::optional<Attribute const>, Exposed>
Chris@16:     {
Chris@16:         typedef Attribute const& type;
Chris@16: 
Chris@16:         template <typename Context>
Chris@16:         static type call(boost::optional<Attribute const> const& attr, Context& ctx)
Chris@16:         {
Chris@16:             return extract_from<Exposed>(boost::get<Attribute const>(attr), ctx);
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     // This handles attributes wrapped inside a boost::ref().
Chris@16:     template <typename Attribute, typename Exposed>
Chris@16:     struct extract_from_attribute<reference_wrapper<Attribute>, Exposed>
Chris@16:     {
Chris@16:         typedef Attribute const& type;
Chris@16: 
Chris@16:         template <typename Context>
Chris@16:         static type call(reference_wrapper<Attribute> const& attr, Context& ctx)
Chris@16:         {
Chris@16:             return extract_from<Exposed>(attr.get(), ctx);
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     template <typename Attribute, typename Exposed, typename Enable>
Chris@16:     struct extract_from_container
Chris@16:     {
Chris@16:         typedef typename traits::container_value<Attribute const>::type
Chris@16:             value_type;
Chris@16:         typedef typename is_convertible<value_type, Exposed>::type
Chris@16:             is_convertible_to_value_type;
Chris@16: 
Chris@16:         typedef typename mpl::if_<
Chris@16:            mpl::or_<
Chris@16:                 is_same<value_type, Exposed>, is_same<Attribute, Exposed> >
Chris@16:           , Exposed const&, Exposed
Chris@16:         >::type type;
Chris@16: 
Chris@16:         // handle case where container value type is convertible to result type
Chris@16:         // we simply return the front element of the container
Chris@16:         template <typename Context, typename Pred>
Chris@16:         static type call(Attribute const& attr, Context&, mpl::true_, Pred)
Chris@16:         {
Chris@16:             // return first element from container
Chris@16:             typedef typename traits::container_iterator<Attribute const>::type
Chris@16:                 iterator_type;
Chris@16: 
Chris@16:             iterator_type it = traits::begin(attr);
Chris@16:             type result = *it;
Chris@16:             ++it;
Chris@16:             return result;
Chris@16:         }
Chris@16: 
Chris@16:         // handle strings
Chris@16:         template <typename Iterator>
Chris@16:         static void append_to_string(Exposed& result, Iterator begin, Iterator end)
Chris@16:         {
Chris@16:             for (Iterator i = begin; i != end; ++i)
Chris@16:                 push_back(result, *i);
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Context>
Chris@16:         static type call(Attribute const& attr, Context&, mpl::false_, mpl::true_)
Chris@16:         {
Chris@16:             typedef typename char_type_of<Attribute>::type char_type;
Chris@16: 
Chris@16:             Exposed result;
Chris@16:             append_to_string(result, traits::get_begin<char_type>(attr)
Chris@16:               , traits::get_end<char_type>(attr));
Chris@16:             return result;
Chris@16:         }
Chris@16: 
Chris@16:         // everything else gets just passed through
Chris@16:         template <typename Context>
Chris@16:         static type call(Attribute const& attr, Context&, mpl::false_, mpl::false_)
Chris@16:         {
Chris@16:             return type(attr);
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Context>
Chris@16:         static type call(Attribute const& attr, Context& ctx)
Chris@16:         {
Chris@16:             typedef typename mpl::and_<
Chris@16:                 traits::is_string<Exposed>, traits::is_string<Attribute>
Chris@16:             >::type handle_strings;
Chris@16: 
Chris@16:             // return first element from container
Chris@16:             return call(attr, ctx, is_convertible_to_value_type()
Chris@16:               , handle_strings());
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     template <typename Attribute>
Chris@16:     struct extract_from_container<Attribute, Attribute>
Chris@16:     {
Chris@16:         typedef Attribute const& type;
Chris@16: 
Chris@16:         template <typename Context>
Chris@16:         static type call(Attribute const& attr, Context&)
Chris@16:         {
Chris@16:             return attr;
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     namespace detail
Chris@16:     {
Chris@16:         // overload for non-container attributes
Chris@16:         template <typename Exposed, typename Attribute, typename Context>
Chris@16:         inline typename spirit::result_of::extract_from<Exposed, Attribute>::type
Chris@16:         extract_from(Attribute const& attr, Context& ctx, mpl::false_)
Chris@16:         {
Chris@16:             return extract_from_attribute<Attribute, Exposed>::call(attr, ctx);
Chris@16:         }
Chris@16: 
Chris@16:         // overload for containers (but not for variants or optionals
Chris@16:         // holding containers)
Chris@16:         template <typename Exposed, typename Attribute, typename Context>
Chris@16:         inline typename spirit::result_of::extract_from<Exposed, Attribute>::type
Chris@16:         extract_from(Attribute const& attr, Context& ctx, mpl::true_)
Chris@16:         {
Chris@16:             return extract_from_container<Attribute, Exposed>::call(attr, ctx);
Chris@16:         }
Chris@16:     }
Chris@16: 
Chris@16:     template <typename Exposed, typename Attribute, typename Context>
Chris@16:     inline typename spirit::result_of::extract_from<Exposed, Attribute>::type
Chris@16:     extract_from(Attribute const& attr, Context& ctx
Chris@16: #if (defined(__GNUC__) && (__GNUC__ < 4)) || \
Chris@16:     (defined(__APPLE__) && defined(__INTEL_COMPILER))
Chris@16:       , typename enable_if<traits::not_is_unused<Attribute> >::type*
Chris@16: #endif
Chris@16:     )
Chris@16:     {
Chris@16:         typedef typename mpl::and_<
Chris@16:             traits::is_container<Attribute>
Chris@16:           , traits::not_is_variant<Attribute>
Chris@16:           , traits::not_is_optional<Attribute>
Chris@16:         >::type is_not_wrapped_container;
Chris@16: 
Chris@16:         return detail::extract_from<Exposed>(attr, ctx
Chris@16:           , is_not_wrapped_container());
Chris@16:     }
Chris@16: 
Chris@16:     template <typename Exposed, typename Context>
Chris@16:     inline unused_type extract_from(unused_type, Context&)
Chris@16:     {
Chris@16:         return unused;
Chris@16:     }
Chris@16: }}}
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: namespace boost { namespace spirit { namespace result_of
Chris@16: {
Chris@16:     template <typename Exposed, typename Attribute>
Chris@16:     struct extract_from
Chris@16:       : mpl::if_<
Chris@16:             mpl::and_<
Chris@16:                 traits::is_container<Attribute>
Chris@16:               , traits::not_is_variant<Attribute>
Chris@16:               , traits::not_is_optional<Attribute> >
Chris@16:           , traits::extract_from_container<Attribute, Exposed>
Chris@16:           , traits::extract_from_attribute<Attribute, Exposed> >::type
Chris@16:     {};
Chris@16: 
Chris@16:     template <typename Exposed>
Chris@16:     struct extract_from<Exposed, unused_type>
Chris@16:     {
Chris@16:         typedef unused_type type;
Chris@16:     };
Chris@16: 
Chris@16:     template <typename Exposed>
Chris@16:     struct extract_from<Exposed, unused_type const>
Chris@16:     {
Chris@16:         typedef unused_type type;
Chris@16:     };
Chris@16: }}}
Chris@16: 
Chris@16: #endif