1<html><head> 2 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 3 <title>Back-end</title><link rel="stylesheet" href="boostbook.css" type="text/css"><meta name="generator" content="DocBook XSL-NS Stylesheets V1.75.2"><link rel="home" href="index.html" title="Meta State Machine (MSM)"><link rel="up" href="pt02.html" title="Part II. Reference"><link rel="prev" href="re01.html" title="Common headers"><link rel="next" href="re03.html" title="Front-end"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Back-end</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re01.html">Prev</a> </td><th width="60%" align="center">Part II. Reference</th><td width="20%" align="right"> <a accesskey="n" href="re03.html">Next</a></td></tr></table><hr></div><div class="refentry" title="Back-end"><a name="d0e5195"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>Back-end — The back-end headers</p></div><div class="refsect1" title="msm/back/state_machine.hpp"><a name="d0e5201"></a><h2>msm/back/state_machine.hpp</h2><p> This header provides one type, state_machine, MSM's state machine engine 4 implementation.</p><pre class="classsynopsis"> <span class="ooclass"><span class="classname">template <class Derived,class HistoryPolicy=NoHistory,class 5 CompilePolicy=favor_runtime_speed> state_machine</span></span> {<br>}</pre><div class="refsect2" title="Template arguments"><a name="d0e5210"></a><h3> Template arguments </h3><div class="refsect3" title="Derived"><a name="d0e5213"></a><h4> Derived </h4><p>The name of the front-end state machine definition. All three 6 front-ends are possible.</p></div><div class="refsect3" title="HistoryPolicy"><a name="d0e5218"></a><h4> HistoryPolicy </h4><p>The desired history. This can be: AlwaysHistory, NoHistory, 7 ShallowHistory. Default is NoHistory.</p></div><div class="refsect3" title="CompilePolicy"><a name="d0e5223"></a><h4> CompilePolicy </h4><p>The trade-off performance / compile-time. There are two predefined 8 policies, favor_runtime_speed and favor_compile_time. Default is 9 favor_runtime_speed, best performance, longer compile-time. See <a class="link" href="ch03s05.html#backend-tradeof-rt-ct">the backend</a>.</p></div></div><div class="refsect2" title="methods"><a name="d0e5231"></a><h3> methods </h3><div class="refsect3" title="start"><a name="d0e5234"></a><h4>start</h4><p> The start methods must be called before any call to process_event. It 10 activates the entry action of the initial state(s). This allows you to 11 choose when a state machine can start. See <a class="link" href="ch03s05.html#backend-start">backend</a>.</p><code class="methodsynopsis"><span class="methodname">void start</span>(<span class="methodparam"></span>);</code></div><div class="refsect3" title="process_event"><a name="d0e5247"></a><h4>process_event</h4><p>The event processing method implements the double-dispatch. Each call 12 to this function with a new event type instantiates a new dispatch 13 algorithm and increases compile-time.</p><code class="methodsynopsis"><span class="methodname">template <class Event> HandledEnum 14 process_event</span>(<span class="methodparam">Event const&</span>);</code></div><div class="refsect3" title="current_state"><a name="d0e5258"></a><h4>current_state</h4><p>Returns the ids of currently active states. You will typically need it 15 only for debugging or logging purposes.</p><code class="methodsynopsis"><span class="methodname">const int* current_state const</span>(<span class="methodparam"></span>);</code></div><div class="refsect3" title="get_state_by_id"><a name="d0e5268"></a><h4>get_state_by_id</h4><p>Returns the state whose id is given. As all states of a concrete state 16 machine share a common base state, the return value is a base state. If 17 the id corresponds to no state, a null pointer is returned.</p><code class="methodsynopsis"><span class="methodname">const BaseState* get_state_by_id const</span>(<span class="methodparam">int id</span>);</code></div><div class="refsect3" title="is_contained"><a name="d0e5279"></a><h4>is_contained</h4><p>Helper returning true if the state machine is contained as a 18 submachine of another state machine.</p><code class="methodsynopsis"><span class="methodname">bool is_contained const</span>(<span class="methodparam"></span>);</code></div><div class="refsect3" title="get_state"><a name="d0e5289"></a><h4>get_state</h4><p>Returns the required state of the state machine as a pointer. A 19 compile error will occur if the state is not to be found in the state 20 machine.</p><code class="methodsynopsis"><span class="methodname">template <class State> State* get_state</span>(<span class="methodparam"></span>);</code></div><div class="refsect3" title="get_state"><a name="d0e5299"></a><h4>get_state</h4><p>Returns the required state of the state machine as a reference. A 21 compile error will occur if the state is not to be found in the state 22 machine.</p><code class="methodsynopsis"><span class="methodname">template <class State> State& get_state</span>(<span class="methodparam"></span>);</code></div><div class="refsect3" title="is_flag_active"><a name="d0e5309"></a><h4>is_flag_active</h4><p>Returns true if the given flag is currently active. A flag is active 23 if the active state of one region is tagged with this flag (using OR as 24 BinaryOp) or active states of <span class="underline">all</span> 25 regions (using AND as BinaryOp)</p><code class="methodsynopsis"><span class="methodname">template <class Flag,class BinaryOp> bool 26 is_flag_active</span>(<span class="methodparam"></span>);</code></div><div class="refsect3" title="is_flag_active"><a name="d0e5322"></a><h4>is_flag_active</h4><p>Returns true if the given flag is currently active. A flag is active 27 if the active state of one region is tagged with this flag.</p><code class="methodsynopsis"><span class="methodname">template <class Flag> bool is_flag_active</span>(<span class="methodparam"></span>);</code></div><div class="refsect3" title="visit_current_states"><a name="d0e5332"></a><h4>visit_current_states</h4><p>Visits all active states and their substates. A state is visited using 28 the <code class="code">accept</code> method without argument. The base class of all 29 states must provide an <code class="code">accept_sig</code> type.</p><code class="methodsynopsis"><span class="methodname">void visit_current_states</span>(<span class="methodparam"></span>);</code></div><div class="refsect3" title="visit_current_states"><a name="d0e5348"></a><h4>visit_current_states</h4><p>Visits all active states and their substates. A state is visited using 30 the <code class="code">accept</code> method with arguments. The base class of all 31 states must provide an <code class="code">accept_sig</code> type defining the 32 signature and thus the number and type of the parameters.</p><code class="methodsynopsis"><span class="methodname">void visit_current_states</span>(<span class="methodparam">any-type param1, any-type param2,...</span>);</code></div><div class="refsect3" title="defer_event"><a name="d0e5365"></a><h4>defer_event</h4><p> Defers the provided event. This method can be called only if at least 33 one state defers an event or if the state machine provides the 34 <code class="code">activate_deferred_events</code>(see <a class="link" href="examples/Orthogonal-deferred2.cpp" target="_top">example</a>) type 35 either directly or using the deferred_events configuration of eUML 36 (<code class="code">configure_ << deferred_events</code>)</p><code class="methodsynopsis"><span class="methodname">template <class Event> void defer_event</span>(<span class="methodparam">Event const&</span>);</code></div></div><div class="refsect2" title="Types"><a name="d0e5385"></a><h3>Types</h3><div class="refsect3" title="nr_regions"><a name="d0e5388"></a><h4>nr_regions </h4><p>The number of orthogonal regions contained in the state machine</p></div><div class="refsect3" title="entry_pt"><a name="d0e5393"></a><h4>entry_pt</h4><p>This nested type provides the necessary typedef for entry point 37 pseudostates. 38 <code class="code">state_machine<...>::entry_pt<state_name></code> is a 39 transition's valid target inside the containing state machine's 40 transition table.</p><pre class="classsynopsis"> <span class="ooclass"><span class="classname">entry_pt</span></span> {<br>}</pre></div><div class="refsect3" title="exit_pt"><a name="d0e5405"></a><h4>exit_pt</h4><p>This nested type provides the necessary typedef for exit point 41 pseudostates. <code class="code">state_machine<...>::exit_pt<state_name></code> 42 is a transition's valid source inside the containing state machine's 43 transition table.</p><pre class="classsynopsis"> <span class="ooclass"><span class="classname">exit_pt</span></span> {<br>}</pre></div><div class="refsect3" title="direct"><a name="d0e5417"></a><h4>direct</h4><p>This nested type provides the necessary typedef for an explicit entry 44 inside a submachine. 45 <code class="code">state_machine<...>::direct<state_name></code> is a 46 transition's valid target inside the containing state machine's 47 transition table.</p><pre class="classsynopsis"> <span class="ooclass"><span class="classname">direct</span></span> {<br>}</pre></div><div class="refsect3" title="stt"><a name="d0e5429"></a><h4>stt</h4><p>Calling state_machine<frontend>::stt returns a mpl::vector 48 containing the transition table of the state machine. This type can then 49 be used with generate_state_set or generate_event_set.</p></div></div></div><div class="refsect1" title="args.hpp"><a name="d0e5434"></a><h2>args.hpp</h2><p>This header provides one type, args. which provides the necessary types for a 50 visitor implementation.</p></div><div class="refsect1" title="msm/back/history_policies.hpp"><a name="d0e5439"></a><h2><span class="command"><strong><a name="history-interface"></a></strong></span>msm/back/history_policies.hpp</h2><p>This header provides the out-of-the-box history policies supported by MSM. 51 There are 3 such policies.</p><div class="refsect2" title="Every history policy must implement the following methods:"><a name="d0e5445"></a><h3>Every history policy must implement the following methods: </h3><div class="refsect3" title="set_initial_states"><a name="d0e5448"></a><h4> set_initial_states </h4><p> This method is called by msm::back::state_machine when constructed. 52 It gives the policy a chance to save the ids of all initial states 53 (passed as array).</p><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void set_initial_states(</code></td><td><code>)</code>;</td><td> </td></tr></table><div class="paramdef-list"><code> 54 <code>(</code>int* const<code>)</code> 55 </code>;</div><div class="funcprototype-spacer"> </div></div></div><div class="refsect3" title="history_exit"><a name="d0e5462"></a><h4> history_exit </h4><p>This method is called by msm::back::state_machine when the submachine 56 is exited. It gives the policy a chance to remember the ids of the last 57 active substates of this submachine (passed as array).</p><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void history_exit(</code></td><td><code>)</code>;</td><td> </td></tr></table><div class="paramdef-list"><code> 58 <code>(</code>int* const<code>)</code> 59 </code>;</div><div class="funcprototype-spacer"> </div></div></div><div class="refsect3" title="history_entry"><a name="d0e5476"></a><h4> history_entry </h4><p>This method is called by msm::back::state_machine when the submachine 60 is entered. It gives the policy a chance to set the active states 61 according to the policy's aim. The policy gets as parameter the event 62 which activated the submachine and returns an array of active states 63 ids.</p><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">template <class Event> int* const history_exit(</code></td><td><code>)</code>;</td><td> </td></tr></table><div class="paramdef-list"><code> 64 <code>(</code>Event const&<code>)</code> 65 </code>;</div><div class="funcprototype-spacer"> </div></div></div></div><div class="refsect2" title="Out-of-the-box policies:"><a name="d0e5490"></a><h3>Out-of-the-box policies: </h3><div class="refsect3" title="NoHistory"><a name="d0e5493"></a><h4>NoHistory</h4><p>This policy is the default used by state_machine. No active state of a 66 submachine is remembered and at every new activation of the submachine, 67 the initial state(s) are activated. </p></div><div class="refsect3" title="AlwaysHistory"><a name="d0e5498"></a><h4>AlwaysHistory</h4><p>This policy is a non-UML-standard extension. The active state(s) of a 68 submachine is (are) always remembered at every new activation of the 69 submachine. </p></div><div class="refsect3" title="ShallowHistory"><a name="d0e5503"></a><h4>ShallowHistory</h4><p>This policy activates the active state(s) of a submachine if the event 70 is found in the policy's event list. </p></div></div></div><div class="refsect1" title="msm/back/default_compile_policy.hpp"><a name="d0e5508"></a><h2>msm/back/default_compile_policy.hpp</h2><p>This header contains the definition of favor_runtime_speed. This policy has 71 two settings:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Submachines dispatch faster because their transitions are added 72 into their containing machine's transition table instead of simply 73 forwarding events.</p></li><li class="listitem"><p>It solves transition conflicts at compile-time</p></li></ul></div></div><div class="refsect1" title="msm/back/favor_compile_time.hpp"><a name="d0e5520"></a><h2>msm/back/favor_compile_time.hpp</h2><p>This header contains the definition of favor_compile_time. This policy has two settings:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Submachines dispatch is slower because all events, even those with 74 no dispatch chance, are forwarded to submachines. In exchange, no 75 row is added into the containing machine's transition table, which 76 reduces compile-time.</p></li><li class="listitem"><p>It solves transition conflicts at run-time.</p></li></ul></div></div><div class="refsect1" title="msm/back/metafunctions.hpp"><a name="d0e5532"></a><h2>msm/back/metafunctions.hpp </h2><p>This header contains metafunctions for use by the library. Three metafunctions 77 can be useful for the user:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="code">generate_state_set< stt ></code>: generates the list of 78 all states referenced by the transition table stt. If stt is a 79 recursive table (generated by 80 <code class="code">recursive_get_transition_table</code>), the metafunction 81 finds recursively all states of the submachines. A non-recursive 82 table can be obtained with some_backend_fsm::stt.</p></li><li class="listitem"><p><code class="code">generate_event_set< stt></code>: generates the list of 83 all events referenced by the transition table stt. If stt is a 84 recursive table (generated by 85 <code class="code">recursive_get_transition_table</code>), the metafunction 86 finds recursively all events of the submachines. A non-recursive 87 table can be obtained with some_backend_fsm::stt.</p></li><li class="listitem"><p><code class="code">recursive_get_transition_table<fsm></code>: recursively 88 extends the transition table of the state machine fsm with tables 89 from the submachines.</p></li></ul></div></div><div class="refsect1" title="msm/back/tools.hpp"><a name="d0e5559"></a><h2>msm/back/tools.hpp </h2><p> This header contains a few metaprogramming tools to get some information out 90 of a state machine.</p><div class="refsect2" title="fill_state_names"><a name="d0e5564"></a><h3>fill_state_names </h3><div class="refsect3" title="attributes"><a name="d0e5567"></a><h4>attributes </h4><p> fill_state_names has for attribute:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="code">char const** m_names</code>: an already allocated 91 array of const char* where the typeid-generated names of a 92 state machine states will be witten.</p></li></ul></div></div><div class="refsect3" title="constructor"><a name="d0e5578"></a><h4>constructor </h4><code class="constructorsynopsis"><span class="methodparam">char const** names_to_fill</span>(<span class="methodparam">char const** names_to_fill</span>);</code></div><div class="refsect3" title="usage"><a name="d0e5585"></a><h4>usage</h4><p> fill_state_names is made for use in a mpl::for_each iterating on a 93 state list and writing inside a pre-allocated array the state names. 94 Example:</p><pre class="programlisting">typedef some_fsm::stt Stt; 95typedef msm::back::generate_state_set<Stt>::type all_states; //states 96static char const* state_names[mpl::size<all_states>::value]; 97// array to fill with names 98// fill the names of the states defined in the state machine 99mpl::for_each<all_states,boost::msm::wrap<mpl::placeholders::_1> > 100 (msm::back::fill_state_names<Stt>(state_names)); 101// display all active states 102for (unsigned int i=0;i<some_fsm::nr_regions::value;++i) 103{ 104 std::cout << " -> " 105 << state_names[my_fsm_instance.current_state()[i]] 106 << std::endl; 107}</pre></div></div><div class="refsect2" title="get_state_name"><a name="d0e5592"></a><h3>get_state_name </h3><div class="refsect3" title="attributes"><a name="d0e5595"></a><h4> attributes </h4><p>get_state_name has for attributes:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>std::string& m_name: the return value of the 108 iteration</p></li><li class="listitem"><p>int m_state_id: the searched state's id</p></li></ul></div></div><div class="refsect3" title="constructor"><a name="d0e5607"></a><h4>constructor</h4><p>The constructor takes as argument a reference to the string to fill 109 with the state name and the id which must be searched.</p><code class="constructorsynopsis"><span class="methodparam">string& name_to_fill,int state_id</span>(<span class="methodparam">string& name_to_fill,int state_id</span>);</code></div><div class="refsect3" title="usage"><a name="d0e5616"></a><h4> usage</h4><p>This type is made for the same search as in the previous example, 110 using a mpl::for_each to iterate on states. After the iteration, the 111 state name reference has been set.</p><pre class="programlisting">// we need a fsm's table 112typedef player::stt Stt; 113typedef msm::back::generate_state_set<Stt>::type all_states; //all states 114std::string name_of_open; // id of Open is 1 115// fill name_of_open for state of id 1 116boost::mpl::for_each<all_states,boost::msm::wrap<mpl::placeholders::_1> > 117 (msm::back::get_state_name<Stt>(name_of_open,1)); 118std::cout << "typeid-generated name Open is: " << name_of_open << std::endl;</pre></div></div><div class="refsect2" title="display_type"><a name="d0e5623"></a><h3>display_type </h3><div class="refsect3" title="attributes"><a name="d0e5626"></a><h4> attributes </h4><p>none</p></div><div class="refsect3" title="usage"><a name="d0e5631"></a><h4> usage</h4><p>Reusing the state list from the previous example, we can output all 119 state names:</p><p><code class="code">mpl::for_each<all_states,boost::msm::wrap<mpl::placeholders::_1> 120 >(msm::back::display_type ());</code></p></div></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re01.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pt02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Common headers </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Front-end</td></tr></table></div></body></html>