Chris@16: //-----------------------------------------------------------------------------
Chris@16: // boost variant/detail/visitation_impl.hpp header file
Chris@16: // See http://www.boost.org for updates, documentation, and revision history.
Chris@16: //-----------------------------------------------------------------------------
Chris@16: //
Chris@16: // Copyright (c) 2003
Chris@16: // Eric Friedman
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_VARIANT_DETAIL_VISITATION_IMPL_HPP
Chris@16: #define BOOST_VARIANT_DETAIL_VISITATION_IMPL_HPP
Chris@16: 
Chris@16: #include "boost/config.hpp"
Chris@16: 
Chris@16: #include "boost/variant/detail/backup_holder.hpp"
Chris@16: #include "boost/variant/detail/cast_storage.hpp"
Chris@16: #include "boost/variant/detail/forced_return.hpp"
Chris@16: #include "boost/variant/detail/generic_result_type.hpp"
Chris@101: #include "boost/variant/variant_fwd.hpp" // for BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
Chris@16: 
Chris@16: #include "boost/mpl/eval_if.hpp"
Chris@16: #include "boost/mpl/bool.hpp"
Chris@16: #include "boost/mpl/identity.hpp"
Chris@16: #include "boost/mpl/int.hpp"
Chris@16: #include "boost/mpl/next.hpp"
Chris@16: #include "boost/mpl/deref.hpp"
Chris@16: #include "boost/mpl/or.hpp"
Chris@16: #include "boost/preprocessor/cat.hpp"
Chris@16: #include "boost/preprocessor/inc.hpp"
Chris@16: #include "boost/preprocessor/repeat.hpp"
Chris@16: #include "boost/type_traits/is_same.hpp"
Chris@16: #include "boost/type_traits/has_nothrow_copy.hpp"
Chris@16: #include "boost/type_traits/is_nothrow_move_constructible.hpp"
Chris@16: 
Chris@16: #if BOOST_WORKAROUND(BOOST_MSVC, >= 1400) 
Chris@16: # pragma warning (push) 
Chris@16: # pragma warning (disable : 4702) //unreachable code 
Chris@16: #endif
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // BOOST_VARIANT_VISITATION_UNROLLING_LIMIT
Chris@16: //
Chris@16: // Unrolls variant's visitation mechanism to reduce template instantiation
Chris@16: // and potentially increase runtime performance. (TODO: Investigate further.)
Chris@16: //
Chris@16: #if !defined(BOOST_VARIANT_VISITATION_UNROLLING_LIMIT)
Chris@101: 
Chris@101: #ifndef BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
Chris@101: #   include "boost/mpl/limits/list.hpp"
Chris@101: #   define BOOST_VARIANT_VISITATION_UNROLLING_LIMIT   \
Chris@101:         BOOST_MPL_LIMIT_LIST_SIZE
Chris@101: #else
Chris@16: #   define BOOST_VARIANT_VISITATION_UNROLLING_LIMIT   \
Chris@16:         BOOST_VARIANT_LIMIT_TYPES
Chris@16: #endif
Chris@16: 
Chris@101: #endif
Chris@101: 
Chris@16: namespace boost {
Chris@16: namespace detail { namespace variant {
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // (detail) class apply_visitor_unrolled
Chris@16: //
Chris@16: // Tag type indicates when visitation_impl is unrolled.
Chris@16: //
Chris@16: struct apply_visitor_unrolled {};
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // (detail) class template visitation_impl_step
Chris@16: //
Chris@16: // "Never ending" iterator range facilitates visitation_impl unrolling.
Chris@16: //
Chris@16: 
Chris@16: 
Chris@16: template <typename Iter, typename LastIter>
Chris@16: struct visitation_impl_step
Chris@16: {
Chris@16:     typedef typename mpl::deref<Iter>::type type;
Chris@16: 
Chris@16:     typedef typename mpl::next<Iter>::type next_iter;
Chris@16:     typedef visitation_impl_step<
Chris@16:           next_iter, LastIter
Chris@16:         > next;
Chris@16: };
Chris@16: 
Chris@16: template <typename LastIter>
Chris@16: struct visitation_impl_step< LastIter,LastIter >
Chris@16: {
Chris@16:     typedef apply_visitor_unrolled type;
Chris@16:     typedef visitation_impl_step next;
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // (detail) function template visitation_impl_invoke
Chris@16: //
Chris@16: // Invokes the given visitor on the specified type in the given storage.
Chris@16: //
Chris@16: 
Chris@16: template <typename Visitor, typename VoidPtrCV, typename T>
Chris@16: inline
Chris@16:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
Chris@16: visitation_impl_invoke_impl(
Chris@16:       int, Visitor& visitor, VoidPtrCV storage, T*
Chris@16:     , mpl::true_// never_uses_backup
Chris@16:     )
Chris@16: {
Chris@16:     return visitor.internal_visit(
Chris@16:           cast_storage<T>(storage), 1L
Chris@16:         );
Chris@16: }
Chris@16: 
Chris@16: template <typename Visitor, typename VoidPtrCV, typename T>
Chris@16: inline
Chris@16:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
Chris@16: visitation_impl_invoke_impl(
Chris@16:       int internal_which, Visitor& visitor, VoidPtrCV storage, T*
Chris@16:     , mpl::false_// never_uses_backup
Chris@16:     )
Chris@16: {
Chris@16:     if (internal_which >= 0)
Chris@16:     {
Chris@16:         return visitor.internal_visit(
Chris@16:               cast_storage<T>(storage), 1L
Chris@16:             );
Chris@16:     }
Chris@16:     else
Chris@16:     {
Chris@16:         return visitor.internal_visit(
Chris@16:               cast_storage< backup_holder<T> >(storage), 1L
Chris@16:             );
Chris@16:     }
Chris@16: }
Chris@16: 
Chris@16: template <typename Visitor, typename VoidPtrCV, typename T, typename NoBackupFlag>
Chris@16: inline
Chris@16:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
Chris@16: visitation_impl_invoke(
Chris@16:       int internal_which, Visitor& visitor, VoidPtrCV storage, T* t
Chris@16:     , NoBackupFlag
Chris@16:     , int
Chris@16:     )
Chris@16: {
Chris@16:     typedef typename mpl::or_<
Chris@16:           NoBackupFlag
Chris@16:         , is_nothrow_move_constructible<T>
Chris@16:         , has_nothrow_copy<T>
Chris@16:         >::type never_uses_backup;
Chris@16: 
Chris@16:     return (visitation_impl_invoke_impl)(
Chris@16:           internal_which, visitor, storage, t
Chris@16:         , never_uses_backup()
Chris@16:         );
Chris@16: }
Chris@16: 
Chris@16: template <typename Visitor, typename VoidPtrCV, typename NBF>
Chris@16: inline
Chris@16:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
Chris@16: visitation_impl_invoke(int, Visitor&, VoidPtrCV, apply_visitor_unrolled*, NBF, long)
Chris@16: {
Chris@101:     // should never be here at runtime!
Chris@16:     typedef typename Visitor::result_type result_type;
Chris@16:     return ::boost::detail::variant::forced_return< result_type >();
Chris@16: }
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // (detail) function template visitation_impl
Chris@16: //
Chris@16: // Invokes the given visitor on the type in the given variant storage.
Chris@16: //
Chris@16: 
Chris@16: template <
Chris@16:       typename W, typename S
Chris@16:     , typename Visitor, typename VPCV
Chris@16:     , typename NBF
Chris@16:     >
Chris@16: inline
Chris@16:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
Chris@16: visitation_impl(
Chris@16:       int, int, Visitor&, VPCV
Chris@16:     , mpl::true_ // is_apply_visitor_unrolled
Chris@16:     , NBF, W* = 0, S* = 0
Chris@16:     )
Chris@16: {
Chris@101:     // should never be here at runtime!
Chris@16:     typedef typename Visitor::result_type result_type;
Chris@16:     return ::boost::detail::variant::forced_return< result_type >();
Chris@16: }
Chris@16: 
Chris@16: template <
Chris@16:       typename Which, typename step0
Chris@16:     , typename Visitor, typename VoidPtrCV
Chris@16:     , typename NoBackupFlag
Chris@16:     >
Chris@16: inline
Chris@16:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
Chris@16: visitation_impl(
Chris@16:       const int internal_which, const int logical_which
Chris@16:     , Visitor& visitor, VoidPtrCV storage
Chris@16:     , mpl::false_ // is_apply_visitor_unrolled
Chris@16:     , NoBackupFlag no_backup_flag
Chris@16:     , Which* = 0, step0* = 0
Chris@16:     )
Chris@16: {
Chris@16:     // Typedef apply_visitor_unrolled steps and associated types...
Chris@16: #   define BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_TYPEDEF(z, N, _) \
Chris@16:     typedef typename BOOST_PP_CAT(step,N)::type BOOST_PP_CAT(T,N); \
Chris@16:     typedef typename BOOST_PP_CAT(step,N)::next \
Chris@16:         BOOST_PP_CAT(step, BOOST_PP_INC(N)); \
Chris@16:     /**/
Chris@16: 
Chris@16:     BOOST_PP_REPEAT(
Chris@16:           BOOST_VARIANT_VISITATION_UNROLLING_LIMIT
Chris@16:         , BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_TYPEDEF
Chris@16:         , _
Chris@16:         )
Chris@16: 
Chris@16: #   undef BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_TYPEDEF
Chris@16: 
Chris@16:     // ...switch on the target which-index value...
Chris@16:     switch (logical_which)
Chris@16:     {
Chris@16: 
Chris@16:     // ...applying the appropriate case:
Chris@16: #   define BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_CASE(z, N, _) \
Chris@16:     case (Which::value + (N)): \
Chris@16:         return (visitation_impl_invoke)( \
Chris@16:               internal_which, visitor, storage \
Chris@16:             , static_cast<BOOST_PP_CAT(T,N)*>(0) \
Chris@16:             , no_backup_flag, 1L \
Chris@16:             ); \
Chris@16:     /**/
Chris@16: 
Chris@16:     BOOST_PP_REPEAT(
Chris@16:           BOOST_VARIANT_VISITATION_UNROLLING_LIMIT
Chris@16:         , BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_CASE
Chris@16:         , _
Chris@16:         )
Chris@16: 
Chris@16: #   undef BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_CASE
Chris@16: 
Chris@16:     default: break;
Chris@16:     }
Chris@16: 
Chris@16:     // If not handled in this iteration, continue unrolling:
Chris@16:     typedef mpl::int_<
Chris@16:           Which::value + (BOOST_VARIANT_VISITATION_UNROLLING_LIMIT)
Chris@16:         > next_which;
Chris@16: 
Chris@16:     typedef BOOST_PP_CAT(step, BOOST_VARIANT_VISITATION_UNROLLING_LIMIT)
Chris@16:         next_step;
Chris@16: 
Chris@16:     typedef typename next_step::type next_type;
Chris@16:     typedef typename is_same< next_type,apply_visitor_unrolled >::type
Chris@16:         is_apply_visitor_unrolled;
Chris@16: 
Chris@16:     return visitation_impl(
Chris@16:           internal_which, logical_which
Chris@16:         , visitor, storage
Chris@16:         , is_apply_visitor_unrolled()
Chris@16:         , no_backup_flag
Chris@16:         , static_cast<next_which*>(0), static_cast<next_step*>(0)
Chris@16:         );
Chris@16: }
Chris@16: 
Chris@16: }} // namespace detail::variant
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)  
Chris@16: # pragma warning(pop)  
Chris@16: #endif 
Chris@16: 
Chris@16: #endif // BOOST_VARIANT_DETAIL_VISITATION_IMPL_HPP