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- //
- // 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)
- //
- #include "boost/mpl/int.hpp"
- #include "boost/mpl/fold.hpp"
- #include "boost/mpl/prior.hpp"
- #include "boost/mpl/count.hpp"
- #include "boost/mpl/insert.hpp"
- #include <boost/mpl/greater.hpp>
- #include <boost/mpl/for_each.hpp>
- #include <boost/mpl/filter_view.hpp>
- #include "boost/mpl/vector/vector20.hpp"
- #include "boost/assert.hpp"
- #include <boost/type_traits/is_same.hpp>
- #include <vector>
- #include <ctime>
- #include <iostream>
- #if defined(BOOST_DINKUMWARE_STDLIB) && BOOST_DINKUMWARE_STDLIB < 310
- namespace std { using ::clock_t; }
- #endif
- namespace mpl = boost::mpl;
- using namespace mpl::placeholders;
- // A metafunction that returns the Event associated with a transition.
- template <class Transition>
- struct transition_event
- {
- typedef typename Transition::event type;
- };
- // A metafunction computing the maximum of a transition's source and
- // end states.
- template <class Transition>
- struct transition_max_state
- {
- typedef typename mpl::int_<
- (Transition::current_state > Transition::next_state)
- ? Transition::current_state
- : Transition::next_state
- > type;
- };
- template<class Derived>
- class state_machine;
- // Generates a singleton runtime lookup table that maps current state
- // to a function that makes the FSM take its transition on the given
- // Event type.
- template <class Fsm, int initial_state, class Stt, class Event>
- struct dispatch_table
- {
- private:
- // This is a table of these function pointers.
- typedef int (*cell)(Fsm&, int, Event const&);
- // Compute the maximum state value in the Fsm so we know how big
- // to make the table
- BOOST_STATIC_CONSTANT(
- int, max_state = (
- mpl::fold<Stt
- , mpl::int_<initial_state>
- , mpl::if_<
- mpl::greater<transition_max_state<_2>,_1>
- , transition_max_state<_2>
- , _1
- >
- >::type::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_)
- {}
-
- // Cell initializer function object, used with mpl::for_each
- template <class Transition>
- void operator()(Transition const&) const
- {
- self->entries[Transition::current_state] = &Transition::execute;
- }
-
- dispatch_table* self;
- };
-
- public:
- // initialize the dispatch table for a given Event and Fsm
- dispatch_table()
- {
- // Initialize cells for no transition
- for (int i = 0; i <= max_state; ++i)
- {
- // VC7.1 seems to need the two-phase assignment.
- cell call_no_transition = &state_machine<Fsm>::call_no_transition;
- entries[i] = call_no_transition;
- }
- // Go back and fill in cells for matching transitions.
- mpl::for_each<
- mpl::filter_view<
- Stt
- , boost::is_same<transition_event<_>, Event>
- >
- >(init_cell(this));
- }
- // The singleton instance.
- static const dispatch_table instance;
- public: // data members
- cell entries[max_state + 1];
- };
- // This declares the statically-initialized dispatch_table instance.
- template <class Fsm, int initial_state, class Stt, class Event>
- const dispatch_table<Fsm, initial_state, Stt, Event>
- dispatch_table<Fsm, initial_state, Stt, Event>::instance;
- // CRTP base class for state machines. Pass the actual FSM class as
- // the Derived parameter.
- template<class Derived>
- class state_machine
- {
- public: // Member functions
-
- // Main function used by clients of the derived FSM to make
- // transitions.
- template<class Event>
- int process_event(Event const& evt)
- {
- typedef typename Derived::transition_table stt;
- typedef dispatch_table<Derived, Derived::initial_state,stt,Event> table;
-
- // Call the action
- return this->m_state
- = table::instance.entries[this->m_state](
- *static_cast<Derived*>(this), this->m_state, evt);
- }
- // Getter that returns the current state of the FSM
- int current_state() const
- {
- return this->m_state;
- }
- private:
- template <class Fsm, int initial_state, class Stt, class Event>
- friend class dispatch_table;
-
- template <class Event>
- static int call_no_transition(Derived& fsm, int state, Event const& e)
- {
- return fsm.no_transition(state, e);
- }
- // Default no-transition handler. Can be replaced in the Derived
- // FSM class.
- template <class Event>
- int no_transition(int state, Event const& e)
- {
- BOOST_ASSERT(false);
- return state;
- }
-
- protected: // interface for the derived class
-
- template<class State>
- state_machine(State state) // Construct with an initial state
- : m_state(state)
- {
- }
- state_machine()
- : m_state(Derived::initial_state) // Construct with the default initial_state
- {
- }
- // Template used to form rows in the transition table
- template<
- int CurrentState
- , class Event
- , int NextState
- , void (Derived::*action)(Event const&)
- >
- struct row
- {
- BOOST_STATIC_CONSTANT(int, current_state = CurrentState);
- BOOST_STATIC_CONSTANT(int, next_state = NextState);
- typedef Event event;
- // Take the transition action and return the next state.
- static int execute(Derived& fsm, int state, Event const& evt)
- {
- BOOST_ASSERT(state == current_state);
- (fsm.*action)(evt);
- return next_state;
- }
- };
- private: // data members
- int m_state;
- };
- namespace // Concrete FSM implementation
- {
- // events
- struct play {};
- struct stop {};
- struct pause {};
- struct open_close {};
- // A "complicated" event type that carries some data.
- struct cd_detected
- {
- cd_detected(std::string name, std::vector<std::clock_t> durations)
- : name(name)
- , track_durations(durations)
- {}
-
- std::string name;
- std::vector<std::clock_t> track_durations;
- };
- // Concrete FSM implementation
- class player : public state_machine<player>
- {
- // The list of FSM states
- enum states {
- Empty, Open, Stopped, Playing, Paused
- , initial_state = Empty
- };
- #ifdef __MWERKS__
- public: // Codewarrior bug workaround. Tested at 0x3202
- #endif
- // transition actions
- void start_playback(play const&) { std::cout << "player::start_playback\n"; }
- void open_drawer(open_close const&) { std::cout << "player::open_drawer\n"; }
- void close_drawer(open_close const&) { std::cout << "player::close_drawer\n"; }
- void store_cd_info(cd_detected const&) { std::cout << "player::store_cd_info\n"; }
- void stop_playback(stop const&) { std::cout << "player::stop_playback\n"; }
- void pause_playback(pause const&) { std::cout << "player::pause_playback\n"; }
- void resume_playback(play const&) { std::cout << "player::resume_playback\n"; }
- void stop_and_open(open_close const&) { std::cout << "player::stop_and_open\n"; }
- #ifdef __MWERKS__
- private:
- #endif
- friend class state_machine<player>;
- typedef player p; // makes transition table cleaner
- // Transition table
- struct transition_table : mpl::vector11<
- // Start Event Next Action
- // +---------+-------------+---------+---------------------+
- row < Stopped , play , Playing , &p::start_playback >,
- row < Stopped , open_close , Open , &p::open_drawer >,
- // +---------+-------------+---------+---------------------+
- row < Open , open_close , Empty , &p::close_drawer >,
- // +---------+-------------+---------+---------------------+
- row < Empty , open_close , Open , &p::open_drawer >,
- row < Empty , cd_detected , Stopped , &p::store_cd_info >,
- // +---------+-------------+---------+---------------------+
- row < Playing , stop , Stopped , &p::stop_playback >,
- row < Playing , pause , Paused , &p::pause_playback >,
- row < Playing , open_close , Open , &p::stop_and_open >,
- // +---------+-------------+---------+---------------------+
- row < Paused , play , Playing , &p::resume_playback >,
- row < Paused , stop , Stopped , &p::stop_playback >,
- row < Paused , open_close , Open , &p::stop_and_open >
- // +---------+-------------+---------+---------------------+
- > {};
- // Replaces the default no-transition response.
- template <class Event>
- int no_transition(int state, Event const& e)
- {
- std::cout << "no transition from state " << state
- << " on event " << typeid(e).name() << std::endl;
- return state;
- }
- };
- //
- // Testing utilities.
- //
- static char const* const state_names[] = { "Empty", "Open", "Stopped", "Playing", "Paused" };
- void pstate(player const& p)
- {
- std::cout << " -> " << state_names[p.current_state()] << std::endl;
- }
-
- void test()
- {
- player p;
- p.process_event(open_close()); pstate(p);
- p.process_event(open_close()); pstate(p);
- p.process_event(
- cd_detected(
- "louie, louie"
- , std::vector<std::clock_t>( /* track lengths */ )
- )
- );
- pstate(p);
-
- p.process_event(play()); pstate(p);
- p.process_event(pause()); pstate(p);
- p.process_event(play()); pstate(p);
- p.process_event(stop()); pstate(p);
- }
- }
- int main()
- {
- test();
- return 0;
- }
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