isyq/fsm

A finite state machine implementation

fsm

A fsm(finite state machine) library, in order to simplify the work of handling state machine.

It's recommended to use FSM instead of if/else or switch code at the scenario with complicated logics.

Feature

• Pure C code
• Clear architecture
• Multiple FSM instances support

Usage

1. Define your STATE, STATE_CALLLBACK_FUNCTION, EVENT and STATE_TRANSITION_FUNCTION.
2. Create a fsm instance by fsm_create().
3. Add states, events and transition functions into fsm.
4. Call fsm_run() at appropriate place.

Example

Take open and close the door as an example.

The state diagram is shown like below:

There are two states: CLOSED and OPENED.

Two events: Open_it and Close_it.

Two transition function: from CLOSED to OPENED and from OPENED to CLOSED.

In the code, we set state:

typedef enum {
    DOOR_STATE_OPENED,
    DOOR_STATE_CLOSED,
} door_state_t;

In the state callback function part, we print out current state name and do nothing else, like this:

void door_opened(void)
{
    i("The door has opened...\r\n");
}

void door_closed(void)
{
    i("The door has closed...\r\n");
}

Now we can get two state variables:

fsm_state_t state_opened   = {DOOR_STATE_OPENED,  door_opened};
fsm_state_t state_closed   = {DOOR_STATE_CLOSED,  door_closed};

In regard to two events, we set like this:

typedef enum {
    DOOR_EVENT_OPEN,
    DOOR_EVENT_CLOSE, 
} door_event_t;

Then transition functions are set like this:

fsm_transition_t door_state_transition_list[] = {
    {state_closed, DOOR_EVENT_OPEN,  state_opened},
    {state_opened, DOOR_EVENT_CLOSE, state_closed},
};

Look into these transition funcitons, they are consisted of current state, event, and next state.

OK, add those stuff into a FSM variable:

fsm_addState(fsm, state_opened);
fsm_addState(fsm, state_closed);

fsm_addEvent(fsm, (fsm_event_t)DOOR_EVENT_OPEN);
fsm_addEvent(fsm, (fsm_event_t)DOOR_EVENT_CLOSE);

for (i = 0; i < door_state_transition_list_count; i++) {
	fsm_addTransition(fsm, door_state_transition_list[i]);    
}

Of course we have to create a FSM variable at the beginning by:

fsm_t* fsm = fsm_create(state_closed);	

Where the parameter is the initializing state.

OK, we can handle state changes like:

fsm_run(fsm, DOOR_EVENT_OPEN);
fsm_run(fsm, DOOR_EVENT_CLOSE);

Our test code is:

fsm_run(fsm, DOOR_EVENT_OPEN);
fsm_run(fsm, DOOR_EVENT_CLOSE);
fsm_run(fsm, DOOR_EVENT_OPEN);
fsm_run(fsm, DOOR_EVENT_OPEN);
fsm_run(fsm, DOOR_EVENT_OPEN);

The result is:


Note

The Heap Size of this project need to set larger than 0x400, as it uses logger library which consumes 0x200 heap memory.