Boost C++ Libraries

libs/msm/doc/HTML/examples/SimpleTutorialEuml.cpp

// Copyright 2010 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)

#include <vector>
#include <iostream>

#include <boost/msm/back/state_machine.hpp>
#include <boost/msm/front/euml/euml.hpp>

using namespace std;
using namespace boost::msm::front::euml;
namespace msm = boost::msm;

// entry/exit/action/guard logging functors
#include "logging_functors.h"

namespace  // Concrete FSM implementation
{
    // events
    BOOST_MSM_EUML_EVENT(play)
    BOOST_MSM_EUML_EVENT(end_pause)
    BOOST_MSM_EUML_EVENT(stop)
    BOOST_MSM_EUML_EVENT(pause)
    BOOST_MSM_EUML_EVENT(open_close)

    // A "complicated" event type that carries some data.
    BOOST_MSM_EUML_DECLARE_ATTRIBUTE(std::string,cd_name)
    BOOST_MSM_EUML_DECLARE_ATTRIBUTE(DiskTypeEnum,cd_type)
    BOOST_MSM_EUML_ATTRIBUTES((attributes_ << cd_name << cd_type ), cd_detected_attributes)
    BOOST_MSM_EUML_EVENT_WITH_ATTRIBUTES(cd_detected,cd_detected_attributes)

    // Concrete FSM implementation 
    // The list of FSM states
    // state not needing any entry or exit
    BOOST_MSM_EUML_STATE((),Paused)

    // it is also possible to define a state which you can implement normally
    // just make it a state, as usual, and also a grammar terminal, euml_state
    struct Empty_impl : public msm::front::state<> , public euml_state<Empty_impl>
    {
        // this allows us to add some functions
        void activate_empty() {std::cout << "switching to Empty " << std::endl;}
        // standard entry behavior
        template <class Event,class FSM>
        void on_entry(Event const& evt,FSM& fsm) 
        {
            std::cout << "entering: Empty" << std::endl;
        }
        template <class Event,class FSM>
        void on_exit(Event const& evt,FSM& fsm) 
        {
            std::cout << "leaving: Empty" << std::endl;
        }
    };
    //instance for use in the transition table
    Empty_impl const Empty;

    // create a functor and a eUML function for the activate_empty method from Entry 
    BOOST_MSM_EUML_METHOD(ActivateEmpty_ , activate_empty , activate_empty_ , void , void )

    // define more states
    BOOST_MSM_EUML_STATE(( Open_Entry,Open_Exit ),Open)
    BOOST_MSM_EUML_STATE(( Stopped_Entry,Stopped_Exit ),Stopped)
    BOOST_MSM_EUML_STATE(( Playing_Entry,Playing_Exit ),Playing)

    
    // guard conditions
    BOOST_MSM_EUML_ACTION(good_disk_format)
    {
        template <class FSM,class EVT,class SourceState,class TargetState>
        bool operator()(EVT const& evt,FSM&,SourceState& ,TargetState& )
        {
            // to test a guard condition, let's say we understand only CDs, not DVD
            if (evt.get_attribute(cd_type)!=DISK_CD)
            {
                std::cout << "wrong disk, sorry" << std::endl;
                // just for logging, does not block any transition
                return true;
            }
            std::cout << "good disk" << std::endl;
            return true;
        }
    };
    // it is also possible to use a plain functor, with default-constructor in the transition table
    struct start_play 
    {
        template <class FSM,class EVT,class SourceState,class TargetState>
        void operator()(EVT const& ,FSM&,SourceState& ,TargetState& )
        {
            cout << "player::start_play" << endl;
        }
    };
    // replaces the old transition table
    BOOST_MSM_EUML_TRANSITION_TABLE((
          Playing   == Stopped  + play        / start_play() ,
          Playing   == Paused   + end_pause   / resume_playback,
          //  +------------------------------------------------------------------------------+
          Empty     == Open     + open_close  / (close_drawer,activate_empty_(target_)),
          //  +------------------------------------------------------------------------------+
          Open      == Empty    + open_close  / open_drawer,
          Open      == Paused   + open_close  / stop_and_open,
          Open      == Stopped  + open_close  / open_drawer,
          Open      == Playing  + open_close  / stop_and_open,
          //  +------------------------------------------------------------------------------+
          Paused    == Playing  + pause       / pause_playback,
          //  +------------------------------------------------------------------------------+
          Stopped   == Playing  + stop        / stop_playback,
          Stopped   == Paused   + stop        / stop_playback,
          Stopped   == Empty    + cd_detected [good_disk_format &&
                                                    (event_(cd_type)==Int_<DISK_CD>())] 
                                                  / (store_cd_info,process_(play)),
          Stopped   == Stopped  + stop                            
          //  +------------------------------------------------------------------------------+
         ),transition_table)

    // create a state machine "on the fly"
    BOOST_MSM_EUML_DECLARE_STATE_MACHINE(( transition_table, //STT
                                        init_ << Empty, // Init State
                                        no_action, // Entry
                                        no_action, // Exit
                                        attributes_ << no_attributes_, // Attributes
                                        configure_ << no_configure_, // configuration
                                        Log_No_Transition // no_transition handler
                                        ),
                                      player_) //fsm name

    // or simply, if no no_transition handler needed:
    //BOOST_MSM_EUML_DECLARE_STATE_MACHINE(( transition_table, //STT
    //                                    Empty // Init State
    //                                 ),player_)

    // choice of back-end
    typedef msm::back::state_machine<player_> player;

    //
    // Testing utilities.
    //
    static char const* const state_names[] = { "Stopped", "Paused", "Open", "Empty", "Playing" };
    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();
        // note that we write open_close and not open_close(), like usual. Both are possible with eUML, but 
        // you now have less to type.
        // go to Open, call on_exit on Empty, then action, then on_entry on Open
        p.process_event(open_close); pstate(p);
        p.process_event(open_close); pstate(p);
        // will be rejected, wrong disk type
        p.process_event(
            cd_detected("louie, louie",DISK_DVD)); pstate(p);
        p.process_event(
            cd_detected("louie, louie",DISK_CD)); pstate(p);
        // no need to call play as the previous event does it in its action method
        //p.process_event(play);

        // at this point, Play is active      
        p.process_event(pause); pstate(p);
        // go back to Playing
        p.process_event(end_pause);  pstate(p);
        p.process_event(pause); pstate(p);
        p.process_event(stop);  pstate(p);
        // event leading to the same state
        // no action method called as none is defined in the transition table
        p.process_event(stop);  pstate(p);
        // test call to no_transition
        p.process_event(pause); pstate(p);
    }
}

int main()
{
    test();
    return 0;
}