williamr@2: //-----------------------------------------------------------------------------
williamr@2: // boost variant/detail/visitation_impl.hpp header file
williamr@2: // See http://www.boost.org for updates, documentation, and revision history.
williamr@2: //-----------------------------------------------------------------------------
williamr@2: //
williamr@2: // Copyright (c) 2003
williamr@2: // Eric Friedman
williamr@2: //
williamr@2: // Distributed under the Boost Software License, Version 1.0. (See
williamr@2: // accompanying file LICENSE_1_0.txt or copy at
williamr@2: // http://www.boost.org/LICENSE_1_0.txt)
williamr@2: 
williamr@2: #ifndef BOOST_VARIANT_DETAIL_VISITATION_IMPL_HPP
williamr@2: #define BOOST_VARIANT_DETAIL_VISITATION_IMPL_HPP
williamr@2: 
williamr@2: #include "boost/config.hpp"
williamr@2: 
williamr@2: #include "boost/variant/detail/backup_holder.hpp"
williamr@2: #include "boost/variant/detail/cast_storage.hpp"
williamr@2: #include "boost/variant/detail/forced_return.hpp"
williamr@2: #include "boost/variant/detail/generic_result_type.hpp"
williamr@2: 
williamr@2: #include "boost/assert.hpp"
williamr@2: #include "boost/mpl/eval_if.hpp"
williamr@2: #include "boost/mpl/bool.hpp"
williamr@2: #include "boost/mpl/identity.hpp"
williamr@2: #include "boost/mpl/int.hpp"
williamr@2: #include "boost/mpl/next.hpp"
williamr@2: #include "boost/mpl/deref.hpp"
williamr@2: #include "boost/mpl/or.hpp"
williamr@2: #include "boost/preprocessor/cat.hpp"
williamr@2: #include "boost/preprocessor/inc.hpp"
williamr@2: #include "boost/preprocessor/repeat.hpp"
williamr@2: #include "boost/type_traits/is_same.hpp"
williamr@2: #include "boost/type_traits/has_nothrow_copy.hpp"
williamr@2: #include "boost/variant/detail/has_nothrow_move.hpp"
williamr@2: 
williamr@2: 
williamr@2: ///////////////////////////////////////////////////////////////////////////////
williamr@2: // BOOST_VARIANT_VISITATION_UNROLLING_LIMIT
williamr@2: //
williamr@2: // Unrolls variant's visitation mechanism to reduce template instantiation
williamr@2: // and potentially increase runtime performance. (TODO: Investigate further.)
williamr@2: //
williamr@2: #if !defined(BOOST_VARIANT_VISITATION_UNROLLING_LIMIT)
williamr@2: #   define BOOST_VARIANT_VISITATION_UNROLLING_LIMIT   \
williamr@2:         BOOST_VARIANT_LIMIT_TYPES
williamr@2: #endif
williamr@2: 
williamr@2: namespace boost {
williamr@2: namespace detail { namespace variant {
williamr@2: 
williamr@2: ///////////////////////////////////////////////////////////////////////////////
williamr@2: // (detail) class apply_visitor_unrolled
williamr@2: //
williamr@2: // Tag type indicates when visitation_impl is unrolled.
williamr@2: //
williamr@2: struct apply_visitor_unrolled {};
williamr@2: 
williamr@2: ///////////////////////////////////////////////////////////////////////////////
williamr@2: // (detail) class template visitation_impl_step
williamr@2: //
williamr@2: // "Never ending" iterator range facilitates visitation_impl unrolling.
williamr@2: //
williamr@2: 
williamr@2: #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
williamr@2: 
williamr@2: template <typename Iter, typename LastIter>
williamr@2: struct visitation_impl_step
williamr@2: {
williamr@2:     typedef typename mpl::deref<Iter>::type type;
williamr@2: 
williamr@2:     typedef typename mpl::next<Iter>::type next_iter;
williamr@2:     typedef visitation_impl_step<
williamr@2:           next_iter, LastIter
williamr@2:         > next;
williamr@2: };
williamr@2: 
williamr@2: template <typename LastIter>
williamr@2: struct visitation_impl_step< LastIter,LastIter >
williamr@2: {
williamr@2:     typedef apply_visitor_unrolled type;
williamr@2:     typedef visitation_impl_step next;
williamr@2: };
williamr@2: 
williamr@2: #else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
williamr@2: 
williamr@2: template <typename Iter, typename LastIter>
williamr@2: struct visitation_impl_step
williamr@2: {
williamr@2:     typedef typename mpl::eval_if<
williamr@2:           is_same<Iter, LastIter>
williamr@2:         , mpl::identity<apply_visitor_unrolled>
williamr@2:         , Iter
williamr@2:         >::type type;
williamr@2: 
williamr@2:     typedef typename mpl::eval_if<
williamr@2:           is_same<type, apply_visitor_unrolled> //is_same<Iter, LastIter>
williamr@2:         , mpl::identity<LastIter>
williamr@2:         , mpl::next<Iter>
williamr@2:         >::type next_iter;
williamr@2: 
williamr@2:     typedef visitation_impl_step<
williamr@2:           next_iter, LastIter
williamr@2:         > next;
williamr@2: };
williamr@2: 
williamr@2: #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround
williamr@2: 
williamr@2: ///////////////////////////////////////////////////////////////////////////////
williamr@2: // (detail) function template visitation_impl_invoke
williamr@2: //
williamr@2: // Invokes the given visitor on the specified type in the given storage.
williamr@2: //
williamr@2: 
williamr@2: template <typename Visitor, typename VoidPtrCV, typename T>
williamr@2: inline
williamr@2:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
williamr@2: visitation_impl_invoke_impl(
williamr@2:       int, Visitor& visitor, VoidPtrCV storage, T*
williamr@2:     , mpl::true_// never_uses_backup
williamr@2:     )
williamr@2: {
williamr@2:     return visitor.internal_visit(
williamr@2:           cast_storage<T>(storage), 1L
williamr@2:         );
williamr@2: }
williamr@2: 
williamr@2: template <typename Visitor, typename VoidPtrCV, typename T>
williamr@2: inline
williamr@2:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
williamr@2: visitation_impl_invoke_impl(
williamr@2:       int internal_which, Visitor& visitor, VoidPtrCV storage, T*
williamr@2:     , mpl::false_// never_uses_backup
williamr@2:     )
williamr@2: {
williamr@2:     if (internal_which >= 0)
williamr@2:     {
williamr@2:         return visitor.internal_visit(
williamr@2:               cast_storage<T>(storage), 1L
williamr@2:             );
williamr@2:     }
williamr@2:     else
williamr@2:     {
williamr@2:         return visitor.internal_visit(
williamr@2:               cast_storage< backup_holder<T> >(storage), 1L
williamr@2:             );
williamr@2:     }
williamr@2: }
williamr@2: 
williamr@2: template <typename Visitor, typename VoidPtrCV, typename T, typename NoBackupFlag>
williamr@2: inline
williamr@2:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
williamr@2: visitation_impl_invoke(
williamr@2:       int internal_which, Visitor& visitor, VoidPtrCV storage, T* t
williamr@2:     , NoBackupFlag
williamr@2:     , int
williamr@2:     )
williamr@2: {
williamr@2:     typedef typename mpl::or_<
williamr@2:           NoBackupFlag
williamr@2:         , has_nothrow_move_constructor<T>
williamr@2:         , has_nothrow_copy<T>
williamr@2:         >::type never_uses_backup;
williamr@2: 
williamr@2:     return visitation_impl_invoke_impl(
williamr@2:           internal_which, visitor, storage, t
williamr@2:         , never_uses_backup()
williamr@2:         );
williamr@2: }
williamr@2: 
williamr@2: template <typename Visitor, typename VoidPtrCV, typename NBF>
williamr@2: inline
williamr@2:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
williamr@2: visitation_impl_invoke(int, Visitor&, VoidPtrCV, apply_visitor_unrolled*, NBF, long)
williamr@2: {
williamr@2:     // should never be here at runtime:
williamr@2:     BOOST_ASSERT(false);
williamr@2:     typedef typename Visitor::result_type result_type;
williamr@2:     return ::boost::detail::variant::forced_return< result_type >();
williamr@2: }
williamr@2: 
williamr@2: ///////////////////////////////////////////////////////////////////////////////
williamr@2: // (detail) function template visitation_impl
williamr@2: //
williamr@2: // Invokes the given visitor on the type in the given variant storage.
williamr@2: //
williamr@2: 
williamr@2: template <
williamr@2:       typename W, typename S
williamr@2:     , typename Visitor, typename VPCV
williamr@2:     , typename NBF
williamr@2:     >
williamr@2: inline
williamr@2:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
williamr@2: visitation_impl(
williamr@2:       int, int, Visitor&, VPCV
williamr@2:     , mpl::true_ // is_apply_visitor_unrolled
williamr@2:     , NBF, W* = 0, S* = 0
williamr@2:     )
williamr@2: {
williamr@2:     // should never be here at runtime:
williamr@2:     BOOST_ASSERT(false);
williamr@2:     typedef typename Visitor::result_type result_type;
williamr@2:     return ::boost::detail::variant::forced_return< result_type >();
williamr@2: }
williamr@2: 
williamr@2: template <
williamr@2:       typename Which, typename step0
williamr@2:     , typename Visitor, typename VoidPtrCV
williamr@2:     , typename NoBackupFlag
williamr@2:     >
williamr@2: inline
williamr@2:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
williamr@2: visitation_impl(
williamr@2:       const int internal_which, const int logical_which
williamr@2:     , Visitor& visitor, VoidPtrCV storage
williamr@2:     , mpl::false_ // is_apply_visitor_unrolled
williamr@2:     , NoBackupFlag no_backup_flag
williamr@2:     , Which* = 0, step0* = 0
williamr@2:     )
williamr@2: {
williamr@2:     // Typedef apply_visitor_unrolled steps and associated types...
williamr@2: #   define BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_TYPEDEF(z, N, _) \
williamr@2:     typedef typename BOOST_PP_CAT(step,N)::type BOOST_PP_CAT(T,N); \
williamr@2:     typedef typename BOOST_PP_CAT(step,N)::next \
williamr@2:         BOOST_PP_CAT(step, BOOST_PP_INC(N)); \
williamr@2:     /**/
williamr@2: 
williamr@2:     BOOST_PP_REPEAT(
williamr@2:           BOOST_VARIANT_VISITATION_UNROLLING_LIMIT
williamr@2:         , BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_TYPEDEF
williamr@2:         , _
williamr@2:         )
williamr@2: 
williamr@2: #   undef BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_TYPEDEF
williamr@2: 
williamr@2:     // ...switch on the target which-index value...
williamr@2:     switch (logical_which)
williamr@2:     {
williamr@2: 
williamr@2:     // ...applying the appropriate case:
williamr@2: #   define BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_CASE(z, N, _) \
williamr@2:     case (Which::value + (N)): \
williamr@2:         return visitation_impl_invoke( \
williamr@2:               internal_which, visitor, storage \
williamr@2:             , static_cast<BOOST_PP_CAT(T,N)*>(0) \
williamr@2:             , no_backup_flag, 1L \
williamr@2:             ); \
williamr@2:     /**/
williamr@2: 
williamr@2:     BOOST_PP_REPEAT(
williamr@2:           BOOST_VARIANT_VISITATION_UNROLLING_LIMIT
williamr@2:         , BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_CASE
williamr@2:         , _
williamr@2:         )
williamr@2: 
williamr@2: #   undef BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_CASE
williamr@2: 
williamr@2:     }
williamr@2: 
williamr@2:     // If not handled in this iteration, continue unrolling:
williamr@2:     typedef mpl::int_<
williamr@2:           Which::value + (BOOST_VARIANT_VISITATION_UNROLLING_LIMIT)
williamr@2:         > next_which;
williamr@2: 
williamr@2:     typedef BOOST_PP_CAT(step, BOOST_VARIANT_VISITATION_UNROLLING_LIMIT)
williamr@2:         next_step;
williamr@2: 
williamr@2:     typedef typename next_step::type next_type;
williamr@2:     typedef typename is_same< next_type,apply_visitor_unrolled >::type
williamr@2:         is_apply_visitor_unrolled;
williamr@2: 
williamr@2:     return visitation_impl(
williamr@2:           internal_which, logical_which
williamr@2:         , visitor, storage
williamr@2:         , is_apply_visitor_unrolled()
williamr@2:         , no_backup_flag
williamr@2:         , static_cast<next_which*>(0), static_cast<next_step*>(0)
williamr@2:         );
williamr@2: }
williamr@2: 
williamr@2: }} // namespace detail::variant
williamr@2: } // namespace boost
williamr@2: 
williamr@2: #endif // BOOST_VARIANT_DETAIL_VISITATION_IMPL_HPP