ceph/src/boost/libs/msm/doc/PDF/examples/AnonymousTutorial.cpp

   1 // Copyright 2010 Christophe Henry
   2 // henry UNDERSCORE christophe AT hotmail DOT com
   3 // This is an extended version of the state machine available in the boost::mpl library
   4 // Distributed under the same license as the original.
   5 // Copyright for the original version:
   6 // Copyright 2005 David Abrahams and Aleksey Gurtovoy. Distributed
   7 // under the Boost Software License, Version 1.0. (See accompanying
   8 // file LICENSE_1_0.txt or copy at
   9 // http://www.boost.org/LICENSE_1_0.txt)
  10
  11 #include <iostream>
  12 // back-end
  13 #include <boost/msm/back/state_machine.hpp>
  14 //front-end
  15 #include <boost/msm/front/state_machine_def.hpp>
  16
  17 namespace msm = boost::msm;
  18 namespace mpl = boost::mpl;
  19 using namespace boost::msm::front;
  20
  21 namespace
  22 {
  23     // events
  24     struct event1 {};
  25
  26
  27     // front-end: define the FSM structure
  28     struct my_machine_ : public msm::front::state_machine_def<my_machine_>
  29     {
  30         // The list of FSM states
  31         struct State1 : public msm::front::state<>
  32         {
  33             // every (optional) entry/exit methods get the event passed.
  34             template <class Event,class FSM>
  35             void on_entry(Event const&,FSM& ) {std::cout << "entering: State1" << std::endl;}
  36             template <class Event,class FSM>
  37             void on_exit(Event const&,FSM& ) {std::cout << "leaving: State1" << std::endl;}
  38         };
  39         struct State2 : public msm::front::state<>
  40         {
  41             template <class Event,class FSM>
  42             void on_entry(Event const& ,FSM&) {std::cout << "entering: State2" << std::endl;}
  43             template <class Event,class FSM>
  44             void on_exit(Event const&,FSM& ) {std::cout << "leaving: State2" << std::endl;}
  45         };
  46
  47         struct State3 : public msm::front::state<>
  48         {
  49             // when stopped, the CD is loaded
  50             template <class Event,class FSM>
  51             void on_entry(Event const& ,FSM&) {std::cout << "entering: State3" << std::endl;}
  52             template <class Event,class FSM>
  53             void on_exit(Event const&,FSM& ) {std::cout << "leaving: State3" << std::endl;}
  54         };
  55
  56         struct State4 : public msm::front::state<>
  57         {
  58             template <class Event,class FSM>
  59             void on_entry(Event const&,FSM& ) {std::cout << "entering: State4" << std::endl;}
  60             template <class Event,class FSM>
  61             void on_exit(Event const&,FSM& ) {std::cout << "leaving: State4" << std::endl;}
  62         };
  63
  64         // the initial state of the player SM. Must be defined
  65         typedef State1 initial_state;
  66
  67         // transition actions
  68         void State2ToState3(none const&)       { std::cout << "my_machine::State2ToState3\n"; }
  69         void State3ToState4(none const&)       { std::cout << "my_machine::State3ToState4\n"; }
  70         // guard conditions
  71         bool always_true(none const& evt)
  72         {
  73             std::cout << "always_true" << std::endl;
  74             return true;
  75         }
  76         bool always_false(none const& evt)
  77         {
  78             std::cout << "always_false" << std::endl;
  79             return false;
  80         }
  81
  82         typedef my_machine_ p; // makes transition table cleaner
  83
  84         // Transition table for player
  85         struct transition_table : mpl::vector<
  86             //    Start     Event         Next      Action               Guard
  87             //  +---------+-------------+---------+---------------------+----------------------+
  88            _row < State1  , none        , State2                                               >,
  89           a_row < State2  , none        , State3  , &p::State2ToState3                         >,
  90             //  +---------+-------------+---------+---------------------+----------------------+
  91             row < State3  , none        , State4  , &p::State3ToState4  , &p::always_true      >,
  92           g_row < State3  , none        , State4                        , &p::always_false     >,
  93            _row < State4  , event1      , State1                                               >
  94             //  +---------+-------------+---------+---------------------+----------------------+
  95         > {};
  96         // Replaces the default no-transition response.
  97         template <class FSM,class Event>
  98         void no_transition(Event const& e, FSM&,int state)
  99         {
 100             std::cout << "no transition from state " << state
 101                 << " on event " << typeid(e).name() << std::endl;
 102         }
 103     };
 104     // Pick a back-end
 105     typedef msm::back::state_machine<my_machine_> my_machine;
 106
 107     //
 108     // Testing utilities.
 109     //
 110     static char const* const state_names[] = { "State1", "State2", "State3", "State4" };
 111     void pstate(my_machine const& p)
 112     {
 113         std::cout << " -> " << state_names[p.current_state()[0]] << std::endl;
 114     }
 115
 116     void test()
 117     {
 118         my_machine p;
 119
 120         // needed to start the highest-level SM. This will call on_entry and mark the start of the SM
 121         // in this case it will also immediately trigger all anonymous transitions
 122         p.start();
 123         // this event will bring us back to the initial state and thus, a new "loop" will be started
 124         p.process_event(event1());
 125
 126     }
 127 }
 128
 129 int main()
 130 {
 131     test();
 132     return 0;
 133 }