int lookahead(void* p, int level) {
void* const q = work.data();
while (level >= 1) {
for (int b = 1; b < 2; ++b) {
spec.get_copy(q, p);
if (spec.get_child(q, level, b) != 0) {
spec.destruct(q);
return level;
}
spec.destruct(q);
}
level = spec.get_child(p, level, 0);
}
return level;
}
void get_copy(void* to, void const* from) {
spec.get_copy(to, from);
}