327 lines
9.9 KiB
C++
327 lines
9.9 KiB
C++
//
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// Copyright 2005 David Abrahams and Aleksey Gurtovoy. Distributed
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// under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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#include "boost/mpl/int.hpp"
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#include "boost/mpl/fold.hpp"
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#include "boost/mpl/prior.hpp"
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#include "boost/mpl/count.hpp"
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#include "boost/mpl/insert.hpp"
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#include <boost/mpl/greater.hpp>
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#include <boost/mpl/for_each.hpp>
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#include <boost/mpl/filter_view.hpp>
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#include "boost/mpl/vector/vector20.hpp"
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#include "boost/assert.hpp"
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#include <boost/type_traits/is_same.hpp>
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#include <vector>
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#include <ctime>
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#include <iostream>
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#if defined(BOOST_DINKUMWARE_STDLIB) && BOOST_DINKUMWARE_STDLIB < 310
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namespace std { using ::clock_t; }
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#endif
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namespace mpl = boost::mpl;
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using namespace mpl::placeholders;
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// A metafunction that returns the Event associated with a transition.
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template <class Transition>
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struct transition_event
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{
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typedef typename Transition::event type;
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};
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// A metafunction computing the maximum of a transition's source and
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// end states.
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template <class Transition>
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struct transition_max_state
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{
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typedef typename mpl::int_<
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(Transition::current_state > Transition::next_state)
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? Transition::current_state
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: Transition::next_state
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> type;
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};
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template<class Derived>
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class state_machine;
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// Generates a singleton runtime lookup table that maps current state
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// to a function that makes the FSM take its transition on the given
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// Event type.
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template <class Fsm, int initial_state, class Stt, class Event>
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struct dispatch_table
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{
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private:
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// This is a table of these function pointers.
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typedef int (*cell)(Fsm&, int, Event const&);
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// Compute the maximum state value in the Fsm so we know how big
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// to make the table
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BOOST_STATIC_CONSTANT(
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int, max_state = (
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mpl::fold<Stt
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, mpl::int_<initial_state>
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, mpl::if_<
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mpl::greater<transition_max_state<_2>,_1>
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, transition_max_state<_2>
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, _1
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>
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>::type::value
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)
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);
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// A function object for use with mpl::for_each that stuffs
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// transitions into cells.
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struct init_cell
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{
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init_cell(dispatch_table* self_)
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: self(self_)
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{}
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// Cell initializer function object, used with mpl::for_each
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template <class Transition>
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void operator()(Transition const&) const
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{
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self->entries[Transition::current_state] = &Transition::execute;
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}
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dispatch_table* self;
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};
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public:
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// initialize the dispatch table for a given Event and Fsm
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dispatch_table()
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{
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// Initialize cells for no transition
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for (int i = 0; i <= max_state; ++i)
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{
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// VC7.1 seems to need the two-phase assignment.
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cell call_no_transition = &state_machine<Fsm>::call_no_transition;
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entries[i] = call_no_transition;
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}
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// Go back and fill in cells for matching transitions.
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mpl::for_each<
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mpl::filter_view<
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Stt
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, boost::is_same<transition_event<_>, Event>
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>
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>(init_cell(this));
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}
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// The singleton instance.
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static const dispatch_table instance;
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public: // data members
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cell entries[max_state + 1];
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};
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// This declares the statically-initialized dispatch_table instance.
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template <class Fsm, int initial_state, class Stt, class Event>
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const dispatch_table<Fsm, initial_state, Stt, Event>
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dispatch_table<Fsm, initial_state, Stt, Event>::instance;
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// CRTP base class for state machines. Pass the actual FSM class as
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// the Derived parameter.
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template<class Derived>
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class state_machine
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{
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public: // Member functions
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// Main function used by clients of the derived FSM to make
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// transitions.
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template<class Event>
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int process_event(Event const& evt)
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{
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typedef typename Derived::transition_table stt;
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typedef dispatch_table<Derived, Derived::initial_state,stt,Event> table;
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// Call the action
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return this->m_state
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= table::instance.entries[this->m_state](
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*static_cast<Derived*>(this), this->m_state, evt);
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}
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// Getter that returns the current state of the FSM
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int current_state() const
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{
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return this->m_state;
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}
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private:
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template <class Fsm, int initial_state, class Stt, class Event>
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friend class dispatch_table;
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template <class Event>
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static int call_no_transition(Derived& fsm, int state, Event const& e)
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{
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return fsm.no_transition(state, e);
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}
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// Default no-transition handler. Can be replaced in the Derived
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// FSM class.
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template <class Event>
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int no_transition(int state, Event const& e)
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{
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BOOST_ASSERT(false);
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return state;
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}
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protected: // interface for the derived class
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template<class State>
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state_machine(State state) // Construct with an initial state
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: m_state(state)
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{
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}
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state_machine()
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: m_state(Derived::initial_state) // Construct with the default initial_state
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{
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}
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// Template used to form rows in the transition table
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template<
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int CurrentState
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, class Event
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, int NextState
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, void (Derived::*action)(Event const&)
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>
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struct row
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{
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BOOST_STATIC_CONSTANT(int, current_state = CurrentState);
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BOOST_STATIC_CONSTANT(int, next_state = NextState);
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typedef Event event;
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// Take the transition action and return the next state.
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static int execute(Derived& fsm, int state, Event const& evt)
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{
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BOOST_ASSERT(state == current_state);
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(fsm.*action)(evt);
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return next_state;
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}
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};
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private: // data members
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int m_state;
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};
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namespace // Concrete FSM implementation
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{
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// events
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struct play {};
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struct stop {};
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struct pause {};
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struct open_close {};
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// A "complicated" event type that carries some data.
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struct cd_detected
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{
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cd_detected(std::string name, std::vector<std::clock_t> durations)
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: name(name)
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, track_durations(durations)
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{}
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std::string name;
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std::vector<std::clock_t> track_durations;
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};
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// Concrete FSM implementation
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class player : public state_machine<player>
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{
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// The list of FSM states
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enum states {
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Empty, Open, Stopped, Playing, Paused
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, initial_state = Empty
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};
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#ifdef __MWERKS__
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public: // Codewarrior bug workaround. Tested at 0x3202
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#endif
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// transition actions
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void start_playback(play const&) { std::cout << "player::start_playback\n"; }
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void open_drawer(open_close const&) { std::cout << "player::open_drawer\n"; }
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void close_drawer(open_close const&) { std::cout << "player::close_drawer\n"; }
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void store_cd_info(cd_detected const&) { std::cout << "player::store_cd_info\n"; }
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void stop_playback(stop const&) { std::cout << "player::stop_playback\n"; }
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void pause_playback(pause const&) { std::cout << "player::pause_playback\n"; }
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void resume_playback(play const&) { std::cout << "player::resume_playback\n"; }
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void stop_and_open(open_close const&) { std::cout << "player::stop_and_open\n"; }
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#ifdef __MWERKS__
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private:
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#endif
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friend class state_machine<player>;
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typedef player p; // makes transition table cleaner
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// Transition table
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struct transition_table : mpl::vector11<
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// Start Event Next Action
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// +---------+-------------+---------+---------------------+
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row < Stopped , play , Playing , &p::start_playback >,
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row < Stopped , open_close , Open , &p::open_drawer >,
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// +---------+-------------+---------+---------------------+
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row < Open , open_close , Empty , &p::close_drawer >,
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// +---------+-------------+---------+---------------------+
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row < Empty , open_close , Open , &p::open_drawer >,
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row < Empty , cd_detected , Stopped , &p::store_cd_info >,
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// +---------+-------------+---------+---------------------+
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row < Playing , stop , Stopped , &p::stop_playback >,
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row < Playing , pause , Paused , &p::pause_playback >,
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row < Playing , open_close , Open , &p::stop_and_open >,
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// +---------+-------------+---------+---------------------+
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row < Paused , play , Playing , &p::resume_playback >,
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row < Paused , stop , Stopped , &p::stop_playback >,
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row < Paused , open_close , Open , &p::stop_and_open >
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// +---------+-------------+---------+---------------------+
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> {};
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// Replaces the default no-transition response.
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template <class Event>
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int no_transition(int state, Event const& e)
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{
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std::cout << "no transition from state " << state
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<< " on event " << typeid(e).name() << std::endl;
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return state;
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}
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};
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//
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// Testing utilities.
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//
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static char const* const state_names[] = { "Empty", "Open", "Stopped", "Playing", "Paused" };
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void pstate(player const& p)
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{
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std::cout << " -> " << state_names[p.current_state()] << std::endl;
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}
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void test()
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{
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player p;
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p.process_event(open_close()); pstate(p);
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p.process_event(open_close()); pstate(p);
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p.process_event(
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cd_detected(
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"louie, louie"
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, std::vector<std::clock_t>( /* track lengths */ )
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)
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);
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pstate(p);
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p.process_event(play()); pstate(p);
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p.process_event(pause()); pstate(p);
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p.process_event(play()); pstate(p);
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p.process_event(stop()); pstate(p);
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}
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}
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int main()
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{
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test();
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return 0;
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}
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