libs/msm/doc/HTML/examples/Serialize.cpp
#include <iostream> // back-end #include <boost/msm/back/state_machine.hpp> //front-end #include <boost/msm/front/state_machine_def.hpp> // include headers that implement a archive in simple text format #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/serialization/tracking.hpp> #include <fstream> namespace msm = boost::msm; namespace mpl = boost::mpl; namespace { // events struct play {}; struct end_pause {}; struct stop {}; struct pause {}; struct open_close {}; // A "complicated" event type that carries some data. enum DiskTypeEnum { DISK_CD=0, DISK_DVD=1 }; struct cd_detected { cd_detected(std::string name, DiskTypeEnum diskType) : name(name), disc_type(diskType) {} std::string name; DiskTypeEnum disc_type; }; // front-end: define the FSM structure struct player_ : public msm::front::state_machine_def<player_> { //we might want to serialize some data contained by the front-end int front_end_data; player_():front_end_data(0){} // to achieve this, ask for it typedef int do_serialize; // and provide a serialize template<class Archive> void serialize(Archive & ar, const unsigned int ) { ar & front_end_data; } // The list of FSM states struct Empty : public msm::front::state<> { // we want Empty to be serialized typedef int do_serialize; template<class Archive> void serialize(Archive & ar, const unsigned int ) { ar & some_dummy_data; } Empty():some_dummy_data(0){} // every (optional) entry/exit methods get the event passed. template <class Event,class FSM> void on_entry(Event const&,FSM& ) {std::cout << "entering: Empty" << std::endl;} template <class Event,class FSM> void on_exit(Event const&,FSM& ) {std::cout << "leaving: Empty" << std::endl;} int some_dummy_data; }; struct Open : public msm::front::state<> { template <class Event,class FSM> void on_entry(Event const& ,FSM&) {std::cout << "entering: Open" << std::endl;} template <class Event,class FSM> void on_exit(Event const&,FSM& ) {std::cout << "leaving: Open" << std::endl;} }; // sm_ptr still supported but deprecated as functors are a much better way to do the same thing struct Stopped : public msm::front::state<msm::front::default_base_state,msm::front::sm_ptr> { template <class Event,class FSM> void on_entry(Event const& ,FSM&) {std::cout << "entering: Stopped" << std::endl;} template <class Event,class FSM> void on_exit(Event const&,FSM& ) {std::cout << "leaving: Stopped" << std::endl;} void set_sm_ptr(player_* pl) { m_player=pl; } player_* m_player; }; struct Playing : public msm::front::state<> { template <class Event,class FSM> void on_entry(Event const&,FSM& ) {std::cout << "entering: Playing" << std::endl;} template <class Event,class FSM> void on_exit(Event const&,FSM& ) {std::cout << "leaving: Playing" << std::endl;} }; // state not defining any entry or exit struct Paused : public msm::front::state<> { }; // the initial state of the player SM. Must be defined typedef Empty initial_state; // 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(end_pause const&) { std::cout << "player::resume_playback\n"; } void stop_and_open(open_close const&) { std::cout << "player::stop_and_open\n"; } void stopped_again(stop const&) {std::cout << "player::stopped_again\n";} // guard conditions bool good_disk_format(cd_detected const& evt) { // to test a guard condition, let's say we understand only CDs, not DVD if (evt.disc_type != DISK_CD) { std::cout << "wrong disk, sorry" << std::endl; return false; } return true; } // used to show a transition conflict. This guard will simply deactivate one transition and thus // solve the conflict bool auto_start(cd_detected const&) { return false; } typedef player_ p; // makes transition table cleaner // Transition table for player struct transition_table : mpl::vector< // Start Event Next Action Guard // +---------+-------------+---------+---------------------+----------------------+ a_row < Stopped , play , Playing , &p::start_playback >, a_row < Stopped , open_close , Open , &p::open_drawer >, _row < Stopped , stop , Stopped >, // +---------+-------------+---------+---------------------+----------------------+ a_row < Open , open_close , Empty , &p::close_drawer >, // +---------+-------------+---------+---------------------+----------------------+ a_row < Empty , open_close , Open , &p::open_drawer >, row < Empty , cd_detected , Stopped , &p::store_cd_info ,&p::good_disk_format >, row < Empty , cd_detected , Playing , &p::store_cd_info ,&p::auto_start >, // +---------+-------------+---------+---------------------+----------------------+ a_row < Playing , stop , Stopped , &p::stop_playback >, a_row < Playing , pause , Paused , &p::pause_playback >, a_row < Playing , open_close , Open , &p::stop_and_open >, // +---------+-------------+---------+---------------------+----------------------+ a_row < Paused , end_pause , Playing , &p::resume_playback >, a_row < Paused , stop , Stopped , &p::stop_playback >, a_row < Paused , open_close , Open , &p::stop_and_open > // +---------+-------------+---------+---------------------+----------------------+ > {}; // Replaces the default no-transition response. template <class FSM,class Event> void no_transition(Event const& e, FSM&,int state) { std::cout << "no transition from state " << state << " on event " << typeid(e).name() << std::endl; } }; // Pick a back-end typedef msm::back::state_machine<player_> player; // // Testing utilities. // static char const* const state_names[] = { "Stopped", "Open", "Empty", "Playing", "Paused" }; void pstate(player const& p) { std::cout << " -> " << state_names[p.current_state()[0]] << std::endl; } void test() { player p; // needed to start the highest-level SM. This will call on_entry and mark the start of the SM p.start(); p.get_state<player_::Empty&>().some_dummy_data=3; p.front_end_data=4; // go to Open, call on_exit on Empty, then action, then on_entry on Open p.process_event(open_close()); pstate(p); std::ofstream ofs("fsm.txt"); // save fsm to archive (current state is Open) { boost::archive::text_oarchive oa(ofs); // write class instance to archive oa << p; } // reload fsm in state Open player p2; { // create and open an archive for input std::ifstream ifs("fsm.txt"); boost::archive::text_iarchive ia(ifs); // read class state from archive ia >> p2; } // we now use p2 as it was loaded // check that we kept Empty's data value std::cout << "Empty's data should be 3:" << p2.get_state<player_::Empty&>().some_dummy_data << std::endl; std::cout << "front-end data should be 4:" << p2.front_end_data << std::endl; p2.process_event(open_close()); pstate(p2); // will be rejected, wrong disk type p2.process_event( cd_detected("louie, louie",DISK_DVD)); pstate(p2); p2.process_event( cd_detected("louie, louie",DISK_CD)); pstate(p2); p2.process_event(play()); // at this point, Play is active p2.process_event(pause()); pstate(p2); // go back to Playing p2.process_event(end_pause()); pstate(p2); p2.process_event(pause()); pstate(p2); p2.process_event(stop()); pstate(p2); // event leading to the same state // no action method called as it is not present in the transition table p2.process_event(stop()); pstate(p2); } } // eliminate object tracking (even if serialized through a pointer) // at the risk of a programming error creating duplicate objects. // this is to get rid of warning because p is not const BOOST_CLASS_TRACKING(player, boost::serialization::track_never) int main() { test(); return 0; }