ptr2idx
idx = ptr2idx(pf->end);
idx = ptr2idx(ptr);
last_idx = ptr2idx(tail) - 1;
last_idx = ptr2idx(malloc_brk) - 1;
if (page_dir[ptr2idx(pf->page)] != MALLOC_FREE)
if (page_dir[ptr2idx(pf->end)-1] != MALLOC_FREE)
if (p != NULL && page_dir[ptr2idx(p)] != MALLOC_FREE)
idx = ptr2idx(p);
page_dir[ptr2idx(pp)] = bp;
idx = ptr2idx(ptr);