use git_hash::ObjectId; use crate::{    extension::{Signature, Tree},    util::split_at_byte_exclusive,}; pub const SIGNATURE: Signature = *b"TREE"; pub struct NodeId {    /// The id of the directory tree of the associated tree object.    id: git_hash::ObjectId,    /// The amount of non-tree entries contained within, and definitely not zero.    entry_count: u32,} /// A recursive data structurepub fn decode(data: &[u8], object_hash: git_hash::Kind) -> Option<Tree> {    let (tree, data) = one_recursive(data, object_hash.len_in_bytes())?;    assert!(        data.is_empty(),        "BUG: should fully consume the entire tree extension chunk, got {} left",        data.len()    );    Some(tree)} pub fn one_recursive(data: &[u8], hash_len: usize) -> Option<(Tree, &[u8])> {    let (path, data) = split_at_byte_exclusive(data, 0)?;     let (entry_count, data) = split_at_byte_exclusive(data, b' ')?;    let entry_count: u32 = atoi::atoi(entry_count)?;     let (subtree_count, mut data) = split_at_byte_exclusive(data, b'\n')?;    let subtree_count: usize = atoi::atoi(subtree_count)?;     let node_id = (entry_count != 0)        .then(|| {            (data.len() >= hash_len).then(|| {                let (hash, rest) = data.split_at(hash_len);                data = rest;                ObjectId::from(hash)            })        })        .flatten()        .map(|id| NodeId { id, entry_count });     let mut subtrees = Vec::with_capacity(subtree_count);    for _ in 0..subtree_count {        let (tree, rest) = one_recursive(data, hash_len)?;        subtrees.push(tree);        data = rest;    }     Some((        Tree {            id: node_id,            name: path.into(),            children: subtrees,        },        data,    ))} #[cfg(test)]mod tests {    use super::*;     #[test]    fn size_of_tree() {        assert_eq!(std::mem::size_of::<Tree>(), 88);    }}