#include <assert.h>
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

#define BUFSIZE (1024)
static uint8_t some_large_buf[BUFSIZE] = {0};

typedef struct {
    uint8_t *buf;
    size_t   buflen;
    size_t   bufptr;
} fast_alloc_t;

void *fast_alloc(fast_alloc_t *fa, size_t s) {
    if (fa->bufptr + s > fa->buflen) {
        return NULL;
    }
    void *p = fa->buf + fa->bufptr;
    fa->bufptr += s;
    return p;
}

void fast_alloc_init(fast_alloc_t *fa, uint8_t *buf, size_t buflen) {
    fa->buf = buf;
    fa->buflen = buflen;
    fa->bufptr = 0;
}

void fast_alloc_wipe(fast_alloc_t *fa) {
    fa->bufptr = 0;
    memset(fa->buf, 0, fa->buflen);
}

int main(void) {
    fast_alloc_t fa = {0};
    fast_alloc_init(&fa, some_large_buf, BUFSIZE);

    int *a = fast_alloc(&fa, sizeof(int));
    *a = 10;

    int *b = fast_alloc(&fa, sizeof(int));
    *b = INT_MAX;

    printf("Number: %d\n", *a);
    printf("Number: %d\n", *b);
    assert(*a == 10);
    assert(*b == INT_MAX);

    fast_alloc_wipe(&fa);

    printf("Number: %d\n", *a);
    printf("Number: %d\n", *b);
    assert(*a != 10);
    assert(*b != INT_MAX);

    printf("All ok!\n");
}