mpl/example/fsm/state_machine.hpp

//-----------------------------------------------------------------------------
// boost fsm/state_machine.hpp header file
// See http://www.boost.org for updates, documentation, and revision history.
//-----------------------------------------------------------------------------
//
// Copyright (c) 2002
// Aleksey Gurtovoy
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee, 
// provided that the above copyright notice appears in all copies and 
// that both the copyright notice and this permission notice appear in 
// supporting documentation. No representations are made about the 
// suitability of this software for any purpose. It is provided "as is" 
// without express or implied warranty.

#ifndef BOOST_FSM_STATE_MACHINE_INCLUDED
#define BOOST_FSM_STATE_MACHINE_INCLUDED

#include "aux_/event.hpp"
#include "aux_/state.hpp"
#include "aux_/transition.hpp"
#include "aux_/STT_impl_gen.hpp"
#include "boost/shared_ptr.hpp"

#include <queue>
#include <memory>
#include <cassert>

namespace fsm {

template< typename Derived >
class state_machine
{
 private:
    typedef	state_machine self_t;
    typedef aux::base_event base_event_t;
    typedef boost::shared_ptr<base_event_t const> base_event_ptr_t;
    
 public: 
    typedef long state_t;

    template< typename DerivedEvent >
    struct event
        : aux::event<DerivedEvent>
    {
    };

    void process_event(base_event_t const& evt)
    {
        // all internal events should be handled at this point
        assert(!m_events_queue.size());

        // process the external event passed
        do_transition(evt);

        // if the previous transition generated any internal events,
        // process those
        while (m_events_queue.size())
        {
            do_transition(*m_events_queue.front());
            m_events_queue.pop();
        }
    }

    state_t current_state() const
    {
        return m_state;
    }

 protected:
    // interface for the derived class

    state_machine(state_t const& initial_state)
        : m_state(initial_state)
    {
    }

    state_machine()
        : m_state(typename Derived::initial_state())
    {
    }

    virtual	~state_machine()
    {
    }

    void post_event(std::auto_ptr<base_event_t const> evt)
    {
        m_events_queue.push(base_event_ptr_t(evt.release()));
    }

    template<
          long State
        , void (Derived::* invariant_func)() const = 0
        >
    struct state
        : fsm::aux::state<Derived,State,invariant_func>
    {
    };

    template<
          typename From
        , typename Event
        , typename To
        , bool (Derived::* transition_func)(Event const&)
        >
    struct transition
        : aux::transition< Derived,From,Event,To,transition_func >
    {
    };

 private:

    void do_transition(base_event_t const& evt)
    {
        typedef typename Derived::transition_table STT_;
        typedef	typename aux::STT_impl_gen< STT_ >::type STT_impl_;

        m_state = STT_impl_::do_transition(
              static_cast<Derived&>(*this)
            , m_state
            , evt
            );
    }

    state_t	m_state;
    std::queue< base_event_ptr_t > m_events_queue;
};

} // namespace fsm

#endif // BOOST_FSM_STATE_MACHINE_INCLUDED