A simple and minimal C implementation of trie

trie.c

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

// weird exercise  from a friend 

// need to Implement this struct
typedef struct attrib_t {
	struct attrib_t* bytes[256];
	const char *data;
} att;


// need to Implement this function
const char *attrib_get(att **a,const char *attrib)
{
         if (*a == NULL) {
		 fprintf(stderr,"Get on %s from null map\n",attrib);
		 exit(-1);
	 }
	 if (*attrib == '\0') return (*a)->data;
	 return attrib_get(&((*a)->bytes[(int)*attrib]),attrib+1);
}
void attrib_init(att **a) {
	*a = malloc(sizeof(**a));
	memset(*a,0,sizeof(**a));
}

// need to Implement this function
void attrib_set(att **a,const char *attrib,const char *value)
{
   if (*a == NULL) attrib_init(a);
	 if (*attrib == '\0') (*a)->data = value;
	 else attrib_set(&((*a)->bytes[(int)*attrib]),attrib+1,value);
}

// need to Implement this function
void attrib_free(att **a)
{
	int i;
	if (a == NULL || *a == NULL) return;
	for (i=0;i<256;i++) attrib_free(&((*a)->bytes[i]));
	free(*a);
}

int main()
{
    att *a =NULL;
    attrib_set(&a,"user","jhon");
    attrib_set(&a,"mail","jhonSmith@gmail.com");
    attrib_set(&a,"user","Smith");
    printf("user = %s\nmail = %s\n" , attrib_get(&a,"user") , attrib_get(&a,"mail"));
    attrib_free(&a);
    return 0;
}