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@argorain argorain/ptrs.c
Created Apr 6, 2015

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Simple round robin scheduler with table of function pointers.
#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;
}
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