func (t *prefixTree) newChildNode(parent *prefixNode, childIndex int) *prefixNode {
n := &prefixNode{prefixTree: t, Leaf: true}
var key *cf.Bitstring
if parent != nil {
parentKey := parent.Key()
key = cf.NewBitstring(parentKey.BitLen() + t.BitQuantum)
key.SetBytes(parentKey.Bytes())
for j := 0; j < parent.BitQuantum; j++ {
if (1<<uint(j))&childIndex == 0 {
key.Clear(parentKey.BitLen() + j)
} else {
key.Set(parentKey.BitLen() + j)
}
}
} else {
key = cf.NewBitstring(0)
}
n.NodeKey = mustEncodeBitstring(key)
svalues := make([]*cf.Zp, t.NumSamples())
for i := 0; i < len(svalues); i++ {
svalues[i] = cf.Zi(cf.P_SKS, 1)
}
n.NodeSValues = mustEncodeZZarray(svalues)
return n
}
