#include <acts/blob/master/Core/include/Acts/Utilities/FiniteStateMachine.hpp>

Classes
struct	Terminated

Public Types
using	StateVariant = std::variant< Terminated, States...>

Public Member Functions
	FiniteStateMachine ()

	FiniteStateMachine (StateVariant state)

const StateVariant &	getState () const noexcept

template<typename State , typename... Args>
void	setState (State state, Args &&...args)

template<typename S >
bool	is (const S &) const noexcept

template<typename S >
bool	is () const noexcept

bool	terminated () const noexcept

template<typename Event , typename... Args>
void	dispatch (Event &&event, Args &&...args)

Protected Types
using	fsm_base = FiniteStateMachine< Derived, States...>

using	event_return = std::optional< StateVariant >

Protected Member Functions
template<typename Event , typename... Args>
event_return	process_event (Event &&event, Args &&...args)

Private Attributes
StateVariant	m_state

Detailed Description

template<typename Derived, typename... States>
class Acts::FiniteStateMachine< Derived, States >

Implementation of a finite state machine engine

Allows setting up a system of states and transitions between them. States are definedd as empty structs (footprint: 1 byte). Tranitions call functions using overload resolution. This works by subclassing this class, providing the deriving type as the first template argument (CRTP) and providing methods like

```cpp event_return on_event(const S&, const E&); ```

The arguments are the state S and the triggered event E. Their values can be discarded (you can attach values to events of course, if you like) The return type of these functions is effectively std::optional<State>, so you can either return std::nullopt to remain in the same state, or an instance of another state. That state will then become active.

You can also define a method template, which will serve as a catch-all handler (due to the fact that it will match any state/event combination):

```cpp template <typename State, typename Event> event_return on_event(const State&, const Event&) const { return Terminated{}; } ```

If for a given state and event no suitable overload of on_event (and you also haven't defined a catch-all as described above), a transition to Terminated will be triggered. This is essentially equivalent to the method template above.

If this triggers, it will switch to the Terminated state (which is always included in the FSM).

Additionally, the FSM will attempt to call functions like ```cpp void on_enter(const State&); void on_exit(const State&); ``` when entering/exiting a state. This can be used to perform actions regardless of the source or destination state in a transition to a given state. This is also fired in case a transition to Terminated occurs.

The base class also calls ```cpp void on_process(const Event&); void on_process(const State&, const Event&); void on_process(const State1& const Event&, const State2&); ``` during event processing, and allow for things like event and transition logging.

The on_event, on_enter, on_exit and on_process methods need to be implemented exhaustively, i.e. for all state/event combinations. This might require you to add catch-all no-op functions like ```cpp template <typename...Args> event_return on_event(Args&&...args) {} // noop ``` and so on.

The public interface for the user of the FSM are the ```cpp template <typename... Args> void setState(StateVariant state, Args&&... args);

template <typename Event, typename... Args> void dispatch(Event&& event, Args&&... args) { ```

setState triggers a transition to a given state, dispatch triggers processing on an event from the given state. Both will call the appropriate on_exit and on_enter overloads. Both also accept an arbitrary number of additional arguments that are passed to the on_event, on_exit and on_enter overloads.

Template Parameters

Derived	Class deriving from the FSM
States	Argument pack with the state types that the FSM can be handled.

Definition at line 102 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 102 of file FiniteStateMachine.hpp

Member Typedef Documentation

template<typename Derived, typename... States>

using Acts::FiniteStateMachine< Derived, States >::event_return = std::optional<StateVariant>

protected

Definition at line 118 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 118 of file FiniteStateMachine.hpp

template<typename Derived, typename... States>

using Acts::FiniteStateMachine< Derived, States >::fsm_base = FiniteStateMachine<Derived, States...>

protected

Definition at line 116 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 116 of file FiniteStateMachine.hpp

template<typename Derived, typename... States>

using Acts::FiniteStateMachine< Derived, States >::StateVariant = std::variant<Terminated, States...>

Variant type allowing tagged type erased storage of the current state of the FSM.

Definition at line 113 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 113 of file FiniteStateMachine.hpp

Constructor & Destructor Documentation

template<typename Derived, typename... States>

Acts::FiniteStateMachine< Derived, States >::FiniteStateMachine ( )

inline

Default constructor. The default state is taken to be the first in the States template arguments

Definition at line 123 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 123 of file FiniteStateMachine.hpp

template<typename Derived, typename... States>

Acts::FiniteStateMachine< Derived, States >::FiniteStateMachine ( StateVariant state )

inline

Constructor from an explicit state. The FSM is initialized to this state.

Parameters

state Initial state for the FSM.

Definition at line 129 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 129 of file FiniteStateMachine.hpp

Member Function Documentation

template<typename Derived, typename... States>

template<typename Event , typename... Args>

void Acts::FiniteStateMachine< Derived, States >::dispatch	(	Event &&	event,
		Args &&...	args
	)

inline

Public interface to handle an event. Will call the appropriate event handlers and perform any required transitions.

Template Parameters

Event	Type of the event being triggered
Args	Additional arguments being passed to overload handlers.

Parameters

event	Instance of the event being triggere
args	Additional arguments

Definition at line 221 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 221 of file FiniteStateMachine.hpp

template<typename Derived, typename... States>

const StateVariant& Acts::FiniteStateMachine< Derived, States >::getState ( ) const

inlinenoexcept

Get the current state of of the FSM (as a variant).

Returns: StateVariant The current state of the FSM.

Definition at line 133 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 133 of file FiniteStateMachine.hpp

template<typename Derived, typename... States>

template<typename S >

bool Acts::FiniteStateMachine< Derived, States >::is ( const S & ) const

inlinenoexcept

Returns whether the FSM is in the specified state

Template Parameters

State type to check against

Parameters

state State instance to check against

Returns: Whether the FSM is in the given state.

Definition at line 161 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 161 of file FiniteStateMachine.hpp

Referenced by Acts::Test::BOOST_AUTO_TEST_CASE(), ludecy(), luedit(), lujmas(), lustrf(), pybook(), pydecy(), pydocu(), pydump(), pyedit(), pyevol(), pyfact(), pyfill(), pyfscr(), pyhirand(), pyhiremn(), pyhisspa(), pyhist(), pyhistfu(), pyhithia(), pyjmas(), pymihg(), pymihk(), pynull(), pypdpi(), pypdpo(), pyplot(), pyprep(), pyptis(), pyrand(), pyreco(), pyremn(), pysspa(), pystfu(), pystrf(), and pythia().

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template<typename Derived, typename... States>

template<typename S >

bool Acts::FiniteStateMachine< Derived, States >::is ( ) const

inlinenoexcept

Returns whether the FSM is in the specified state. Alternative version directly taking only the template argument.

Template Parameters

State type to check against

Returns: Whether the FSM is in the given state.

Definition at line 170 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 170 of file FiniteStateMachine.hpp

template<typename Derived, typename... States>

template<typename Event , typename... Args>

event_return Acts::FiniteStateMachine< Derived, States >::process_event	(	Event &&	event,
		Args &&...	args
	)

inlineprotected

Handles processing of an event.

Note: This should only be called from inside the class Deriving from FSM.

Template Parameters

Event	Type of the event being processed
Args	Arguments being passed to the overload handlers.

Parameters

event	Instance of the event
args	Additional arguments

Returns: Variant state type, signifying if a transition is supposed to happen.

Definition at line 191 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 191 of file FiniteStateMachine.hpp

Referenced by Acts::FiniteStateMachine< fsm2, states::Disconnected, states::Connected >::dispatch().

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template<typename Derived, typename... States>

template<typename State , typename... Args>

void Acts::FiniteStateMachine< Derived, States >::setState	(	State	state,
		Args &&...	args
	)

inline

Sets the state to a given one. Triggers on_exit and on_enter for the given states.

Template Parameters

State	Type of the target state
Args	Additional arguments passed through callback overloads.

Parameters

state	Instance of the target state
args	The additional arguments

Definition at line 143 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 143 of file FiniteStateMachine.hpp

Referenced by Acts::FiniteStateMachine< fsm2, states::Disconnected, states::Connected >::dispatch().

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template<typename Derived, typename... States>

bool Acts::FiniteStateMachine< Derived, States >::terminated ( ) const

inlinenoexcept

Returns whether the FSM is in the terminated state.

Returns: Whether the FSM is in the terminated state.

Definition at line 179 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 179 of file FiniteStateMachine.hpp

Member Data Documentation

template<typename Derived, typename... States>

StateVariant Acts::FiniteStateMachine< Derived, States >::m_state

private

Definition at line 231 of file FiniteStateMachine.hpp.

View newest version in sPHENIX GitHub at line 231 of file FiniteStateMachine.hpp

Referenced by Acts::FiniteStateMachine< fsm2, states::Disconnected, states::Connected >::getState(), Acts::FiniteStateMachine< fsm2, states::Disconnected, states::Connected >::is(), Acts::FiniteStateMachine< fsm2, states::Disconnected, states::Connected >::process_event(), and Acts::FiniteStateMachine< fsm2, states::Disconnected, states::Connected >::setState().

The documentation for this class was generated from the following file:

acts/blob/master/Core/include/Acts/Utilities/FiniteStateMachine.hpp

Classes

Public Types

Public Member Functions

Protected Types

Protected Member Functions

Private Attributes

Detailed Description

template<typename Derived, typename... States> class Acts::FiniteStateMachine< Derived, States >

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation

template<typename Derived, typename... States>
class Acts::FiniteStateMachine< Derived, States >