#include <stdio.h>
#include <stdint.h>
#include <stddef.h>

#define MAX_DATA_COUNT 32

typedef struct {
    int foo;
    char bar[10];
    float baz;
} my_data_t;

struct {
    my_data_t data;
    uint8_t used;
} my_data_vector[MAX_DATA_COUNT] = {0};

size_t find_empty_data_index() {
    size_t i;
    for (i = 0; i < MAX_DATA_COUNT; i++) {
        if (my_data_vector[i].used == 0) {
            break;
        }
    }
    return i;
}

size_t find_data_index(my_data_t* data) {
    size_t i;
    for (i = 0; i < MAX_DATA_COUNT; i++) {
        if (&my_data_vector[i].data == data) {
            break;
        }
    }
    return i;
}

my_data_t* data_create() {
    size_t index = find_empty_data_index();

    if (index == MAX_DATA_COUNT) {
        return NULL;
    }

    my_data_vector[index].used = 1;
    return &my_data_vector[index].data;
}

void data_delete(my_data_t* data) {
    size_t index = find_data_index(data);

    if (index == MAX_DATA_COUNT) {
        return;
    }

    my_data_vector[index].used = 0;
}

int main() {
    size_t i;
    my_data_t* data1 = data_create();
    for (i = 0; i <= 40; i++) {
        printf("%d\n", find_empty_data_index());
        my_data_t* data = data_create();
        printf("%d - %p\n", find_data_index(data), data);
    }

    data_delete(data1);

    for (i = 0; i <= 40; i++) {
        printf("%d\n", find_empty_data_index());
        my_data_t* data = data_create();
        printf("%d - %p\n", find_data_index(data), data);
    }
}