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// 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 <iostream>
// back-end
#include <boost/msm/back/state_machine.hpp>
//front-end
#include <boost/msm/front/state_machine_def.hpp>
namespace msm = boost::msm;
namespace mpl = boost::mpl;
namespace
{
// events
struct play {};
struct end_pause {};
struct stop {};
struct pause {};
struct open_close {};
struct NextSong {};
struct PreviousSong {};
// A "complicated" event type that carries some data.
struct cd_detected
{
cd_detected(std::string name)
: name(name)
{}
std::string name;
};
// front-end: define the FSM structure
struct player_ : public msm::front::state_machine_def<player_>
{
// The list of FSM states
struct Empty : public msm::front::state<>
{
// 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;}
};
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;}
};
struct Stopped : public msm::front::state<>
{
// when stopped, the CD is loaded
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;}
};
struct Playing_ : public msm::front::state_machine_def<Playing_>
{
// when playing, the CD is loaded and we are in either pause or playing (duh)
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;}
// The list of FSM states
struct Song1 : public msm::front::state<>
{
template <class Event,class FSM>
void on_entry(Event const&,FSM& ) {std::cout << "starting: First song" << std::endl;}
template <class Event,class FSM>
void on_exit(Event const&,FSM& ) {std::cout << "finishing: First Song" << std::endl;}
};
struct Song2 : public msm::front::state<>
{
template <class Event,class FSM>
void on_entry(Event const&,FSM& ) {std::cout << "starting: Second song" << std::endl;}
template <class Event,class FSM>
void on_exit(Event const&,FSM& ) {std::cout << "finishing: Second Song" << std::endl;}
};
struct Song3 : public msm::front::state<>
{
template <class Event,class FSM>
void on_entry(Event const&,FSM& ) {std::cout << "starting: Third song" << std::endl;}
template <class Event,class FSM>
void on_exit(Event const&,FSM& ) {std::cout << "finishing: Third Song" << std::endl;}
};
// the initial state. Must be defined
typedef Song1 initial_state;
// transition actions
void start_next_song(NextSong const&) { std::cout << "Playing::start_next_song\n"; }
void start_prev_song(PreviousSong const&) { std::cout << "Playing::start_prev_song\n"; }
// guard conditions
typedef Playing_ pl; // makes transition table cleaner
// Transition table for Playing
struct transition_table : mpl::vector4<
// Start Event Next Action Guard
// +---------+-------------+---------+---------------------+----------------------+
a_row < Song1 , NextSong , Song2 , &pl::start_next_song >,
a_row < Song2 , PreviousSong, Song1 , &pl::start_prev_song >,
a_row < Song2 , NextSong , Song3 , &pl::start_next_song >,
a_row < Song3 , PreviousSong, Song2 , &pl::start_prev_song >
// +---------+-------------+---------+---------------------+----------------------+
> {};
// 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;
}
};
// back-end
// demonstrates Shallow History: if the state gets activated with end_pause
// then it will remember the last active state and reactivate it
// also possible: AlwaysHistory, the last active state will always be reactivated
// or NoHistory, always restart from the initial state
typedef msm::back::state_machine<Playing_,msm::back::ShallowHistory<mpl::vector<end_pause> > > Playing;
// state not defining any entry or exit
struct Paused : public msm::front::state<>
{
template <class Event,class FSM>
void on_entry(Event const&,FSM& ) {std::cout << "entering: Paused" << std::endl;}
template <class Event,class FSM>
void on_exit(Event const&,FSM& ) {std::cout << "leaving: Paused" << std::endl;}
};
// 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& cd) {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
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 >,
a_row < Stopped , stop , Stopped , &p::stopped_again >,
// +---------+-------------+---------+---------------------+----------------------+
a_row < Open , open_close , Empty , &p::close_drawer >,
// +---------+-------------+---------+---------------------+----------------------+
a_row < Empty , open_close , Open , &p::open_drawer >,
a_row < Empty , cd_detected , Stopped , &p::store_cd_info >,
// +---------+-------------+---------+---------------------+----------------------+
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();
// 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);
p.process_event(cd_detected("louie, louie"));
p.process_event(play());
// at this point, Play is active
// make transition happen inside it. Player has no idea about this event but it's ok.
p.process_event(NextSong());pstate(p); //2nd song active
p.process_event(NextSong());pstate(p);//3rd song active
p.process_event(PreviousSong());pstate(p);//2nd song active
p.process_event(pause()); pstate(p);
// go back to Playing
// as you see, remembers the original state as end_pause is an history trigger
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
p.process_event(stop()); pstate(p);
// play does not trigger shallow history => start back from 1st song
p.process_event(play()); pstate(p);
}
}
int main()
{
test();
return 0;
}
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