PTN_BRANCH_POSITION
const pt_slot_t branch_slot = PTN_BRANCH_POSITION(ptn);
PTN_SET_BRANCH_POSITION(dst, PTN_BRANCH_POSITION(src));
KASSERT(PT_LEAF_P(node) || id->id_parent_slot == PTN_BRANCH_POSITION(ptn));
KASSERT(PT_LEAF_P(node) || id->id_parent_slot == PTN_BRANCH_POSITION(PT_NODE(node)));
KASSERT(PTN_BRANCH_POSITION(ptn) == id.id_parent_slot);
const pt_slot_t branch_slot = PTN_BRANCH_POSITION(target);
if (PTN_BRANCH(parent) == PTN_BRANCH_SLOT(target, PTN_BRANCH_POSITION(parent))) {
const pt_slot_t slot = PTN_BRANCH_POSITION(parent);
PTN_SET_BRANCH_POSITION(parent, PTN_BRANCH_POSITION(target));
PTN__EXTRACT((ptn)->ptn_nodedata, PTN_BRANCH_POSITION)
PTN__INSERT((ptn)->ptn_nodedata, PTN_BRANCH_POSITION, slot)