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/type_traits/is_same.hpp>
#include <boost/msm/event_traits.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));
template <class Transition>
struct convert_event_and_forward
{
static HandledEnum execute(Fsm& fsm, int region_index, int state, Event const& evt)
{
typename Transition::transition_event forwarded(evt);
return Transition::execute(fsm,region_index,state,forwarded);
}
};
// 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 &, ::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] = 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 &, ::boost::mpl::false_ const &) const
{
self->entries[0] = reinterpret_cast<cell>(&Transition::execute);
}
// version for transition event is boost::any
// 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 &, ::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] = &convert_event_and_forward<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 &, ::boost::mpl::true_ const &) const
{
self->entries[0] = &convert_event_and_forward<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 &, ::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 &, ::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>(),
::boost::mpl::bool_<
::boost::msm::is_kleene_event<typename Transition::transition_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!
// case for internal transitions of this fsm
template <class State>
typename ::boost::disable_if<
typename ::boost::is_same<State,Fsm>::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::default_eventless_transition;
tofill_entries[state_id+1] = call_no_transition;
}
template <class State>
typename ::boost::enable_if<
typename ::boost::is_same<State,Fsm>::type
,void>::type
operator()(boost::msm::wrap<State> const&,boost::msm::back::dummy<1> = 0)
{
cell call_no_transition = &Fsm::default_eventless_transition;
tofill_entries[0] = 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::mpl::or_<
::boost::is_base_of<transition_event< ::boost::mpl::placeholders::_>, Event>,
::boost::msm::is_kleene_event<transition_event< ::boost::mpl::placeholders::_> >
>
>,
// 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