ceph/src/boost/libs/msm/doc/HTML/examples/ActiveStateSetBeforeTransition.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
  15 //front-end
  16 #include <boost/msm/front/state_machine_def.hpp>
  17 // functors
  18 #include <boost/msm/front/functor_row.hpp>
  19 #include <boost/msm/front/euml/common.hpp>
  20
  21
  22 using namespace std;
  23 namespace msm = boost::msm;
  24 namespace mpl = boost::mpl;
  25 using namespace msm::front;
  26
  27 namespace  // Concrete FSM implementation
  28 {
  29     // events
  30     struct disconnect {};
  31     struct connect {};
  32
  33     // flag
  34     struct is_connected{};
  35     // front-end: define the FSM structure
  36     struct Connection_ : public msm::front::state_machine_def<Connection_>
  37     {
  38         // when a transition is about to be taken, we already update our currently active state(s)
  39         typedef msm::active_state_switch_before_transition active_state_switch_policy;
  40
  41         // The list of FSM states
  42         struct Connected : public msm::front::state<>
  43         {
  44             // in this state, we are connected
  45             typedef mpl::vector1<is_connected>      flag_list;
  46             template <class Event,class FSM>
  47             void on_entry(Event const&,FSM& ) {std::cout << "entering: Connected" << std::endl;}
  48             template <class Event,class FSM>
  49             void on_exit(Event const&,FSM& ) {std::cout << "leaving: Connected" << std::endl;}
  50         };
  51         struct Disconnected : public msm::front::state<>
  52         {
  53             template <class Event,class FSM>
  54             void on_entry(Event const& ,FSM&) {std::cout << "entering: Disconnected" << std::endl;}
  55             template <class Event,class FSM>
  56             void on_exit(Event const&,FSM& ) {std::cout << "leaving: Disconnected" << std::endl;}
  57         };
  58
  59         // transition actions
  60         struct SignalConnect
  61         {
  62             template <class EVT,class FSM,class SourceState,class TargetState>
  63             void operator()(EVT const&, FSM& fsm,SourceState& ,TargetState& )
  64             {
  65                 // by default, this would be wrong (shows false)
  66                 cout << "SignalConnect. Connected? " << std::boolalpha << fsm.template is_flag_active<is_connected>() << endl;
  67             }
  68         };
  69         struct SignalDisconnect
  70         {
  71             template <class EVT,class FSM,class SourceState,class TargetState>
  72             void operator()(EVT const&, FSM& fsm,SourceState& ,TargetState& )
  73             {
  74                 // by default, this would be wrong (shows true)
  75                 cout << "SignalDisconnect. Connected? " << std::boolalpha << fsm.template is_flag_active<is_connected>() << endl;
  76             }
  77         };
  78
  79         // the initial state of the player SM. Must be defined
  80         typedef Disconnected initial_state;
  81
  82         // Transition table for player
  83         struct transition_table : mpl::vector<
  84             //    Start          Event         Next           Action                     Guard
  85             //  +--------------+-------------+--------------+---------------------------+----------------------+
  86             Row < Connected    , disconnect  , Disconnected , SignalDisconnect          , none                 >,
  87             Row < Disconnected , connect     , Connected    , SignalConnect             , none                 >
  88             //  +--------------+-------------+--------------+---------------------------+----------------------+
  89         > {};
  90         // Replaces the default no-transition response.
  91         template <class FSM,class Event>
  92         void no_transition(Event const& e, FSM&,int state)
  93         {
  94             std::cout << "no transition from state " << state
  95                 << " on event " << typeid(e).name() << std::endl;
  96         }
  97     };
  98     // Pick a back-end
  99     typedef msm::back::state_machine<Connection_> Connection;
 100
 101
 102     void test()
 103     {
 104         Connection connection;
 105         // needed to start the highest-level SM. This will call on_entry and mark the start of the SM
 106         connection.start();
 107         // signal a connection
 108         connection.process_event(connect());
 109         // signal a disconnection
 110         connection.process_event(disconnect());
 111         connection.stop();
 112     }
 113 }
 114
 115 int main()
 116 {
 117     test();
 118     return 0;
 119 }