FSM Support

Description

Macros and classes for writing Finite State Machines. An FSM is defined with the FSM_Switch() macro.

Classes
class	cFSM
	Store the state of an FSM. This class is used in conjunction with the FSM_Switch() and other FSM_ macros. More...

Macros
#define	FSM_MAXT   64
	After this many transitions without reaching a steady state we assume the FSM is in an infinite loop. More...
#define	FSM_Switch(fsm)
	Implements a Finite State Machine. FSM state is stored in an object of type cFSM. More...
#define	FSM_Transient(state)
	Declares a transient state; to be used in enum which declares states. More...
#define	FSM_Steady(state)
	Declares a steady state; to be used in enum which declares states. More...
#define	FSM_Enter(state)
	Within an FSM_Switch() case branch, declares code to be executed on entering the given state. More...
#define	FSM_Exit(state)
	Within an FSM_Switch() case branch, declares code to be executed on exiting the given state. More...
#define	FSM_Goto(fsm, state)
	To be used in state exit code, to transition to another state. More...

Macro Definition Documentation

FSM_MAXT

#define FSM_MAXT   64

After this many transitions without reaching a steady state we assume the FSM is in an infinite loop.

FSM_Switch

#define FSM_Switch

(

fsm

)

Implements a Finite State Machine. FSM state is stored in an object of type cFSM.

There are two kinds of states: transient and steady. At each execution of the FSM_Switch() statement, the FSM transitions out of the current (steady) state, potentially undergoes a series of state changes to transient states, and arrives at another steady state.

The actual FSM is embedded in an FSM_Switch(), which has cases for entering and leaving each state:

FSM_Switch(fsm)
{
    case FSM_Exit(state1):
        //...
        break;
    case FSM_Enter(state1):
        //...
        break;
    case FSM_Exit(state2):
        //...
        break;
    case FSM_Enter(state2):
        //...
        break;
    //...
}

States are declared in enums, using the FSM_Transient() and FSM_Steady() macros.

State transitions are done via calls to FSM_Goto(), which simply stores the new state in the cFSM object.

See also

cFSM, FSM_Transient, FSM_Steady, FSM_Goto, FSM_Debug, FSM_Print

FSM_Transient

#define FSM_Transient

(

state

)

Declares a transient state; to be used in enum which declares states.

Example:

enum {
   INIT = 0,
   SLEEP = FSM_Steady(1),
   ACTIVE = FSM_Steady(2),
   SEND = FSM_Transient(1),
};

The numbers in parens must be unique within the state type and they are used for constructing numeric IDs for the states.

See also

FSM_Steady, FSM_Switch

FSM_Steady

#define FSM_Steady

(

state

)

Declares a steady state; to be used in enum which declares states.

See example in FSM_Transient.

See also

FSM_Transient, FSM_Switch

FSM_Enter

#define FSM_Enter

(

state

)

Within an FSM_Switch() case branch, declares code to be executed on entering the given state.

Calls to FSM_Goto() are not allowed within a state's Enter block.

See also

FSM_Switch

FSM_Exit

#define FSM_Exit

(

state

)

Within an FSM_Switch() case branch, declares code to be executed on exiting the given state.

See also

FSM_Switch

FSM_Goto

#define FSM_Goto	(		fsm,
			state
	)

To be used in state exit code, to transition to another state.

Uses stringize (#state), so it only works correctly if 'state' is the enum name itself and not some variable that contains the state code.

See also

FSM_Switch