boost/msm/back/dispatch_table.hpp
// Copyright 2008 Christophe Henry // henry UNDERSCORE christophe AT hotmail DOT com // This is an extended version of the state machine available in the boost::mpl library // Distributed under the same license as the original. // Copyright for the original version: // Copyright 2005 David Abrahams and Aleksey Gurtovoy. 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) #ifndef BOOST_MSM_BACK_DISPATCH_TABLE_H #define BOOST_MSM_BACK_DISPATCH_TABLE_H #include <utility> #include <boost/mpl/reverse_fold.hpp> #include <boost/mpl/greater.hpp> #include <boost/mpl/filter_view.hpp> #include <boost/mpl/pop_front.hpp> #include <boost/mpl/for_each.hpp> #include <boost/mpl/advance.hpp> #include <boost/type_traits/is_base_of.hpp> #include <boost/msm/back/metafunctions.hpp> #include <boost/msm/back/common_types.hpp> BOOST_MPL_HAS_XXX_TRAIT_DEF(is_frow) namespace boost { namespace msm { namespace back { // Generates a singleton runtime lookup table that maps current state // to a function that makes the SM take its transition on the given // Event type. template <class Fsm,class Stt, class Event,class CompilePolicy> struct dispatch_table { private: // This is a table of these function pointers. typedef HandledEnum (*cell)(Fsm&, int,int,Event const&); typedef bool (*guard)(Fsm&, Event const&); // class used to build a chain (or sequence) of transitions for a given event and start state // (like an UML diamond). Allows transition conflicts. template< typename Seq,typename AnEvent,typename State > struct chain_row { typedef State current_state_type; typedef AnEvent transition_event; // helper for building a disable/enable_if-controlled execute function struct execute_helper { template <class Sequence> static HandledEnum execute(Fsm& , int, int, Event const& , ::boost::mpl::true_ const & ) { // if at least one guard rejected, this will be ignored, otherwise will generate an error return HANDLED_FALSE; } template <class Sequence> static HandledEnum execute(Fsm& fsm, int region_index , int state, Event const& evt, ::boost::mpl::false_ const & ) { // try the first guard typedef typename ::boost::mpl::front<Sequence>::type first_row; HandledEnum res = first_row::execute(fsm,region_index,state,evt); if (HANDLED_TRUE!=res && HANDLED_DEFERRED!=res) { // if the first rejected, move on to the next one HandledEnum sub_res = execute<typename ::boost::mpl::pop_front<Sequence>::type>(fsm,region_index,state,evt, ::boost::mpl::bool_< ::boost::mpl::empty<typename ::boost::mpl::pop_front<Sequence>::type>::type::value>()); // if at least one guards rejects, the event will not generate a call to no_transition if ((HANDLED_FALSE==sub_res) && (HANDLED_GUARD_REJECT==res) ) return HANDLED_GUARD_REJECT; else return sub_res; } return res; } }; // Take the transition action and return the next state. static HandledEnum execute(Fsm& fsm, int region_index, int state, Event const& evt) { // forward to helper return execute_helper::template execute<Seq>(fsm,region_index,state,evt, ::boost::mpl::bool_< ::boost::mpl::empty<Seq>::type::value>()); } }; // nullary metafunction whose only job is to prevent early evaluation of _1 template< typename Entry > struct make_chain_row_from_map_entry { // if we have more than one frow with the same state as source, remove the ones extra // note: we know the frow's are located at the beginning so we remove at the beginning (number of frows - 1) elements enum {number_frows = ::boost::mpl::count_if< typename Entry::second,has_is_frow< ::boost::mpl::placeholders::_1> >::value}; //erases the first NumberToDelete rows template<class Sequence, int NumberToDelete> struct erase_first_rows { typedef typename ::boost::mpl::erase< typename Entry::second, typename ::boost::mpl::begin<Sequence>::type, typename ::boost::mpl::advance< typename ::boost::mpl::begin<Sequence>::type, ::boost::mpl::int_<NumberToDelete> >::type >::type type; }; // if we have more than 1 frow with this event (not allowed), delete the spare typedef typename ::boost::mpl::eval_if< typename ::boost::mpl::bool_< number_frows >= 2 >::type, erase_first_rows<typename Entry::second,number_frows-1>, ::boost::mpl::identity<typename Entry::second> >::type filtered_stt; typedef chain_row<filtered_stt,Event, typename Entry::first > type; }; // helper for lazy evaluation in eval_if of change_frow_event template <class Transition,class NewEvent> struct replace_event { typedef typename Transition::template replace_event<NewEvent>::type type; }; // changes the event type for a frow to the event we are dispatching // this helps ensure that an event does not get processed more than once because of frows and base events. template <class FrowTransition> struct change_frow_event { typedef typename ::boost::mpl::eval_if< typename has_is_frow<FrowTransition>::type, replace_event<FrowTransition,Event>, boost::mpl::identity<FrowTransition> >::type type; }; // Compute the maximum state value in the sm so we know how big // to make the table typedef typename generate_state_set<Stt>::type state_list; BOOST_STATIC_CONSTANT(int, max_state = ( ::boost::mpl::size<state_list>::value)); // A function object for use with mpl::for_each that stuffs // transitions into cells. struct init_cell { init_cell(dispatch_table* self_) : self(self_) {} // version for transition event not base of our event // first for all transitions, then for internal ones of a fsm template <class Transition> typename ::boost::disable_if< typename ::boost::is_same<typename Transition::current_state_type,Fsm>::type ,void>::type init_event_base_case(Transition const&, ::boost::mpl::true_ const &) const { typedef typename create_stt<Fsm>::type stt; BOOST_STATIC_CONSTANT(int, state_id = (get_state_id<stt,typename Transition::current_state_type>::value)); self->entries[state_id+1] = reinterpret_cast<cell>(&Transition::execute); } template <class Transition> typename ::boost::enable_if< typename ::boost::is_same<typename Transition::current_state_type,Fsm>::type ,void>::type init_event_base_case(Transition const&, ::boost::mpl::true_ const &) const { self->entries[0] = reinterpret_cast<cell>(&Transition::execute); } // version for transition event base of our event // first for all transitions, then for internal ones of a fsm template <class Transition> typename ::boost::disable_if< typename ::boost::is_same<typename Transition::current_state_type,Fsm>::type ,void>::type init_event_base_case(Transition const&, ::boost::mpl::false_ const &) const { typedef typename create_stt<Fsm>::type stt; BOOST_STATIC_CONSTANT(int, state_id = (get_state_id<stt,typename Transition::current_state_type>::value)); self->entries[state_id+1] = &Transition::execute; } template <class Transition> typename ::boost::enable_if< typename ::boost::is_same<typename Transition::current_state_type,Fsm>::type ,void>::type init_event_base_case(Transition const&, ::boost::mpl::false_ const &) const { self->entries[0] = &Transition::execute; } // Cell initializer function object, used with mpl::for_each template <class Transition> typename ::boost::enable_if<typename has_not_real_row_tag<Transition>::type,void >::type operator()(Transition const&,boost::msm::back::dummy<0> = 0) const { // version for not real rows. No problem because irrelevant for process_event } template <class Transition> typename ::boost::disable_if<typename has_not_real_row_tag<Transition>::type,void >::type operator()(Transition const& tr,boost::msm::back::dummy<1> = 0) const { //only if the transition event is a base of our event is the reinterpret_case safe init_event_base_case(tr, ::boost::mpl::bool_< ::boost::is_base_of<typename Transition::transition_event,Event>::type::value>() ); } dispatch_table* self; }; // Cell default-initializer function object, used with mpl::for_each // initializes with call_no_transition, defer_transition or default_eventless_transition // variant for non-anonymous transitions template <class EventType,class Enable=void> struct default_init_cell { default_init_cell(dispatch_table* self_,cell* tofill_entries_) : self(self_),tofill_entries(tofill_entries_) {} template <class State> typename ::boost::enable_if<typename has_state_delayed_event<State,Event>::type,void>::type operator()(boost::msm::wrap<State> const&,boost::msm::back::dummy<0> = 0) { typedef typename create_stt<Fsm>::type stt; BOOST_STATIC_CONSTANT(int, state_id = (get_state_id<stt,State>::value)); cell call_no_transition = &Fsm::defer_transition; tofill_entries[state_id+1] = call_no_transition; } template <class State> typename ::boost::disable_if< typename ::boost::mpl::or_< typename has_state_delayed_event<State,Event>::type, typename ::boost::is_same<State,Fsm>::type >::type ,void >::type operator()(boost::msm::wrap<State> const&,boost::msm::back::dummy<1> = 0) { typedef typename create_stt<Fsm>::type stt; BOOST_STATIC_CONSTANT(int, state_id = (get_state_id<stt,State>::value)); cell call_no_transition = &Fsm::call_no_transition; tofill_entries[state_id+1] = call_no_transition; } // case for internal transitions of this fsm template <class State> typename ::boost::enable_if< typename ::boost::mpl::and_< typename ::boost::mpl::not_<typename has_state_delayed_event<State,Event>::type>::type, typename ::boost::is_same<State,Fsm>::type >::type ,void>::type operator()(boost::msm::wrap<State> const&,boost::msm::back::dummy<2> = 0) { cell call_no_transition = &Fsm::call_no_transition_internal; tofill_entries[0] = call_no_transition; } dispatch_table* self; cell* tofill_entries; }; // variant for anonymous transitions template <class EventType> struct default_init_cell<EventType, typename ::boost::enable_if< typename is_completion_event<EventType>::type>::type> { default_init_cell(dispatch_table* self_,cell* tofill_entries_) : self(self_),tofill_entries(tofill_entries_) {} // this event is a compound one (not a real one, just one for use in event-less transitions) // Note this event cannot be used as deferred! template <class State> void operator()(boost::msm::wrap<State> const&) { typedef typename create_stt<Fsm>::type stt; BOOST_STATIC_CONSTANT(int, state_id = (get_state_id<stt,State>::value)); cell call_no_transition = &Fsm::default_eventless_transition; tofill_entries[state_id+1] = call_no_transition; } dispatch_table* self; cell* tofill_entries; }; public: // initialize the dispatch table for a given Event and Fsm dispatch_table() { // Initialize cells for no transition ::boost::mpl::for_each<typename generate_state_set<Stt>::type, boost::msm::wrap< ::boost::mpl::placeholders::_1> > (default_init_cell<Event>(this,entries)); // build chaining rows for rows coming from the same state and the current event // first we build a map of sequence for every source // in reverse order so that the frow's are handled first (UML priority) typedef typename ::boost::mpl::reverse_fold< // filter on event ::boost::mpl::filter_view <Stt, ::boost::is_base_of<transition_event< ::boost::mpl::placeholders::_>, Event> >, // build a map ::boost::mpl::map<>, ::boost::mpl::if_< // if we already have a row on this source state ::boost::mpl::has_key< ::boost::mpl::placeholders::_1, transition_source_type< ::boost::mpl::placeholders::_2> >, // insert a new element in the value type ::boost::mpl::insert< ::boost::mpl::placeholders::_1, ::boost::mpl::pair<transition_source_type< ::boost::mpl::placeholders::_2>, ::boost::mpl::push_back< ::boost::mpl::at< ::boost::mpl::placeholders::_1, transition_source_type< ::boost::mpl::placeholders::_2> >, change_frow_event< ::boost::mpl::placeholders::_2 > > > >, // first row on this source state, make a vector with 1 element ::boost::mpl::insert< ::boost::mpl::placeholders::_1, ::boost::mpl::pair<transition_source_type< ::boost::mpl::placeholders::_2>, make_vector< change_frow_event< ::boost::mpl::placeholders::_2> > > > > >::type map_of_row_seq; // and then build chaining rows for all source states having more than 1 row typedef typename ::boost::mpl::fold< map_of_row_seq,::boost::mpl::vector0<>, ::boost::mpl::if_< ::boost::mpl::greater< ::boost::mpl::size< ::boost::mpl::second< ::boost::mpl::placeholders::_2> >, ::boost::mpl::int_<1> >, // we need row chaining ::boost::mpl::push_back< ::boost::mpl::placeholders::_1, make_chain_row_from_map_entry< ::boost::mpl::placeholders::_2> >, // just one row, no chaining, we rebuild the row like it was before ::boost::mpl::push_back< ::boost::mpl::placeholders::_1, get_first_element_pair_second< ::boost::mpl::placeholders::_2> > > >::type chained_rows; // Go back and fill in cells for matching transitions. ::boost::mpl::for_each<chained_rows>(init_cell(this)); } // The singleton instance. static const dispatch_table instance; public: // data members // +1 => 0 is reserved for this fsm (internal transitions) cell entries[max_state+1]; }; }}} // boost::msm::back #endif //BOOST_MSM_BACK_DISPATCH_TABLE_H