SIZELEFT
if (node_size + sizeof(indx_t) > SIZELEFT(mp)) {
if (delta > 0 && SIZELEFT(mp) < delta) {
if (SIZELEFT(pright->parent) < bt_branch_size(bt, &sepkey)) {
if (SIZELEFT(mp) < bt_leaf_size(bt, key, data)) {
#define PAGEFILL(bt, mp) (1000 * ((bt)->head.psize - PAGEHDRSZ - SIZELEFT(mp)) / \