fsmlib.h

This library is another approach to implement a finite state machine in C.

Implementation should be:

• easy
• well manageable
• well readable
• standardized

Getting Started

Include the header:

#include "fsmlib.h"

Define states:

FSM_STATES(ledHandler,
    sLED_IS_ON,
    sLED_IS_OFF,
    sLED_BLINK
)

Define events:

FSM_EVENTS(ledHandler,
    eLED_TURN_ON,
    eLED_TURN_OFF,
    eLED_SET_TOGGLE,
    eLED_TIMER_TICK
)

Define callback functions:

static FSM_STATE_TYPE(ledHandler) led_turn_off(void* par, void* ret);
static FSM_STATE_TYPE(ledHandler) led_turn_on(void* par, void* ret);
static FSM_STATE_TYPE(ledHandler) led_toggle_mode_set(void* par, void* ret);
static FSM_STATE_TYPE(ledHandler) led_toggle(void* par, void* ret);

Implement the FSM_TABLE as a triplet of {STATE, EVENT, FUNCTION}

FSM_TABLE(ledHandler,
    {sLED_IS_ON , eLED_TURN_OFF,      led_turn_off        },
    {sLED_IS_OFF, eLED_TURN_ON ,      led_turn_on         },
    {sLED_IS_ON , eLED_SET_TOGGLE,    led_toggle_mode_set },
    {sLED_IS_OFF, eLED_SET_TOGGLE,    led_toggle_mode_set },
    {sLED_BLINK,  eLED_TURN_ON ,      led_turn_on         },
    {sLED_BLINK,  eLED_TURN_OFF,      led_turn_off         },
    {sLED_BLINK,  eLED_TIMER_TICK,    led_toggle          }
)

The most important aspect for your application is to generate events that may be given to the state machine. For this example events are entered by the user in a console environment.

int fsm_get_event() {
    int event = getchar();    
    int c;
    while (c = getchar() != '\n' && c!= EOF){}    
    return (event-'0');
}

To run the state machine, call fsm_run(name, event, par, ret). 'par' is meant to pass parameters to your state transition functions and 'ret' to return information. In case the combination of given event and the machines current state is described by FSM_TABLE, the function defined for this combination will be called. The functions must be implemented by the user and return FSM_STATES for the state machine.

int main(void){
    print_instructions();
    while(1){
        print_fsm_error(  
            fsm_run(ledHandler, 
                    fsm_get_event(), 
                    NULL, NULL)
        );
    }
}

For a complete example look at fsmlib_example.c. Just compile it using gcc:

gcc fsmlib_example.c

HAVE FUN!

Tests

It is planned to add unit tests using ceedling

Contributing

Please contact me if you have any suggestions for improvements.

Versioning

The versionnumber gets updated in the License File.

License

This project is licensed under the MIT License - see the LICENSE.txt file for details

Acknowledgment

Thanks to Alexander Kann and Lars Heinrichs for their valuable support.