P::move_next(current.page.as_page(), &mut current.cursor);
                let left = P::left_child(current.page.as_page(), &current.cursor);

                let left = P::right_child(current.page.as_page(), &current.cursor);

                } else {
                    P::move_next(current.page.as_page(), &mut current.cursor);

                P::move_next(current.page.as_page(), &mut current.cursor);

                } else {
                    P::move_next(current.page.as_page(), &mut current.cursor);

                let current = unsafe { &mut *self.stack[self.pointer].as_mut_ptr() };
                P::move_next(current.page.as_page(), &mut current.cursor);

        debug!("======== prev");

            debug!("prev = {:?} {:?} {:?}" ,self.pointer, current.page, current.cursor);

                debug!("empty");

                debug!("current = {:?} {:?}", k, v);

                debug!("pop");

    }
}
#[test]
fn iterators() {
    env_logger::try_init().unwrap_or(());
    let env = Env::new_anon(40960, 1).unwrap();
    let mut txn = Env::mut_txn_begin(&env).unwrap();
    let mut db = create_db_::<MutTxn<&Env, ()>, u64, A, P<u64, A>>(&mut txn).unwrap();
    for i in 0..100 {
        let a = A([i; 100]);
        put(&mut txn, &mut db, &i, &a).unwrap();
    }
    let mut cursor = btree::cursor::Cursor::new(&txn, &db).unwrap();
    for i in 0..50 {
        let (k, v) = cursor.next(&txn).unwrap().unwrap();
        assert_eq!(*k, i);
        assert_eq!(v.0[0], i);
        debug!("{:?}", i);

    crate::debug::debug(&txn, &[&db], "debug", true);
    debug!("=======");
    for i in (25..50).rev() {
        let (k, v) = cursor.prev(&txn).unwrap().unwrap();
        debug!("{:?} {:?}", i, k);
        assert_eq!(*k, i);
        assert_eq!(v.0[0], i);
    }
    debug!("=======");
    for i in 24..75 {
        let (k, v) = cursor.next(&txn).unwrap().unwrap();
        assert_eq!(*k, i);
        assert_eq!(v.0[0], i);
        debug!("{:?}", i);
    }