}

/* shared memory implement */
static MM *mm_create_shm(size_t size) {
  MM *p;

  p = (MM *)mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
  if (p != (MM *)-1) {
    p->size = size;
    p->start = (char *)p + sizeof(MM);
  }
  return p;
}

static void mm_destroy_shm(MM *mm) {
  if (mm != NULL && mm != (MM *)-1) {
    munmap(mm, mm->size);
  }
}

static void mm_init(MM *mm) {
  mm->start = MM_ALIGN(mm->start);
  mm->lock = mm->start;
  mm->start = MM_ALIGN((void *)(((char *)(mm->start)) + sizeof(mm_mutex)));
  mm->available = mm->size - (((char *)(mm->start))-(char *)mm);
  mm->free_list = (mm_free_bucket *)mm->start;
  mm->free_list->size = mm->available;
  mm->free_list->next = NULL;