C state machine

/*
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*/

#include <stdio.h>
#include <stdlib.h>

// State struct
typedef struct{
    void(*Enter)(void*);
    void(*Exit)();
    void(*Update)(float);
    char *name;
}State;

//StateMachine struct
typedef struct{
    State *state;
    State *stateList;
}StateMachine;

void change_state(StateMachine *sm, int stateIndex, void *data){
    sm->state->Exit();
    sm->state = &sm->stateList[stateIndex];
    sm->state->Enter(data);
}

// example data passed to state enter
typedef struct {
    int speed;
}SomeData;

// Example state functions
void st_idle_enter(void *data){
    printf("Idle entered \n");
}
void st_run_enter(void *data){
    int spd = ((SomeData*)data)->speed;
    printf("Run entered with speed data: %d \n", spd);
}
void st_exit(){
    printf("exited \n");
}
void st_update(float dt){
    printf("delta_time: %f \n", dt);
}

// State enum
enum {
    WALK,
    RUN
};

int main(){
    State idle = {st_idle_enter, st_exit, st_update, "idle"};
    State run = {st_run_enter, st_exit, st_update, "run"};
    State list[] = {idle, run};
    StateMachine sm = {&idle, list};

    sm.state->Update(0.666);
    change_state(&sm, WALK, NULL);

    SomeData data = {16};
    change_state(&sm, RUN, (void*)&data);

    return 0;
}