Simple round robin scheduler with table of function pointers.

ptrs.c

#include "stdio.h"

#define MAX_SIZE 10 //maximum amount of functions in table
//#define SHOW_ITERATION  //uncoment for show iteration numbers


//************ TABLES AND ROUTINES *****************************

typedef enum //function callers
{
    FUN_1=0,
    FUN_2,
    FUN_3,
} fun_e;

typedef struct //functon table definition
{
    fun_e fun; ///< identifier
    int	  (*p_fun)(int param); ///< pointer to routine
    int period;
    int timer;
}	fun_table_t;

fun_table_t fun_table[MAX_SIZE]; //function table itself

unsigned int fun_amount=0; //actual amount of functions in table

void init_fun(fun_e fun, int (*p_fun)(int param), int period) //initialization of table. See main ;)
{
    fun_table[fun].fun=fun;
    fun_table[fun].p_fun = *p_fun;
    fun_table[fun].period = period;
    fun_table[fun].timer=0;
    fun_amount++;
}

int call_fun(fun_e fun, int param) //function caller
{
    int i=0;

    for(i=0;i<fun_amount;i++)
    {
        if(fun==fun_table[i].fun)
        {
            return fun_table[i].p_fun(param);
        }
    }
    return -1; //err

}

void init_timers(){ //timer initialization for scheduler
    for(int i=0; i<fun_amount; i++){
        fun_table[i].timer=fun_table[i].period;
    }
}

int check_timer(){ //SW timer checker
    for(int i=0; i<fun_amount; i++){
        if(fun_table[i].timer>0)
            fun_table[i].timer--;
        else {
            fun_table[i].timer=fun_table[i].period;
            fun_table[i].p_fun(i);
        }
    }
}

//*************** FUNCTIONS *****************************************

int fun1(int param){
    printf("Hello from 1st function\n");
    return param;
}

int fun2(int param){
    printf("Hello from 2nd function\n");
    return param*2;
}

int fun3(int param){
    printf("Hello from 3rd function\n");
    return param+2;
}

//*************** MAIN *********************************

int main(int argc, char **argv){
    printf("Function pointers example\n\n");

    init_fun(FUN_1, fun1, 50);
    init_fun(FUN_2, fun2, 100);
    init_fun(FUN_3, fun3, 200);
    printf("Function init OK\n\n");

    printf("Lets try call all functions.\n");
    printf("1. return: %d\n",call_fun(FUN_1, 5));
    printf("2. return: %d\n",call_fun(FUN_2, 5));
    printf("3. return: %d\n",call_fun(FUN_3, 5));
    printf("All OK\n\n");

    printf("Let's try calling by number in loop.\n");
    for(int i=0; i<10; i++){
        printf("%d. return: %d\n",i,call_fun(i, 5));
    }

    printf("\nLet's try simple round-robin scheduler with fixed lifetime.\n");
    init_timers();
    for(int i=0; i<1000; i++){
#ifdef SHOW_ITERATION
        printf("iteration %d\n",i);
#endif
        check_timer();
    }
    printf("\n\nAnd thats all.\n");
    return 0;
}