struct chunk* get_chunk(void *p)
{
    if(p == NULL)
        return NULL;
    /*if((char*)p % sizeof(size_t) != 0)
        return NULL;*/
    struct chunk *base = get_base();
    /* if((struct chunk*)p < base || p > sbrk(0))
        return NULL;*/
    while(base != NULL && base->data != p)
    {
        base = base->next;
    }
    if(base == NULL || base->free == 0)
        return NULL;
    return base;

}