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

typedef struct {
    int value;
} foo_t;

typedef void (*foo_callback_t)(foo_t *foo);

typedef struct _callback_node_s callback_node_t;

struct _callback_node_s {
    foo_callback_t callback;
    callback_node_t *next;
};

static callback_node_t *callback_list = NULL;

void add_foo_callback(foo_callback_t callback)
{
    callback_node_t *node = malloc(sizeof(callback_node_t));
    node->callback = callback;
    node->next = callback_list;
    callback_list = node;
}

void notify_once()
{
    foo_t foo;
    callback_node_t *node;

    foo.value = 10;
    for (node = callback_list; node != NULL; node = node->next)
        node->callback(&foo);
}

void notify_n_times(int n)
{
    int i;

    for (i = 0; i < n; ++i)
        notify_once();
}