Method put

crates/kernel/src/shard.rs:315–327

Preorder serialization: `0u8, id(4)` for a leaf; `1u8, , ` for an internal node.

(&self, out: &mut Vec<u8>)

  pub fn prune(&self, keep: &impl Fn(u32) -> bool) -> Option<AggNode> {
    match self {
      AggNode::Leaf(id) => keep(*id).then_some(AggNode::Leaf(*id)),
      AggNode::Internal(l, r) => match (l.prune(keep), r.prune(keep)) {
        (Some(a), Some(b)) => Some(AggNode::Internal(Box::new(a), Box::new(b))),
        (Some(a), None) | (None, Some(a)) => Some(a),
        (None, None) => None,
      },
    }
  }

  /// Preorder serialization: `0u8, id(4)` for a leaf; `1u8, <left>, <right>` for
  /// an internal node.
  fn put(&self, out: &mut Vec<u8>) {
    match self {
      AggNode::Leaf(id) => {
        out.push(0);
        out.extend_from_slice(&id.to_le_bytes());