extract_bit
next_bit = extract_bit(key->data, node->prefixlen);
next_bit = extract_bit(key->data, node->prefixlen);
next_bit = extract_bit(node->data, matchlen);
if (extract_bit(key->data, matchlen)) {
next_bit = extract_bit(key->data, node->prefixlen);
next_bit = extract_bit(key->data, node->prefixlen);