1 files changed, 63 insertions, 0 deletions
diff --git a/vendor/gix-index/src/extension/tree/decode.rs b/vendor/gix-index/src/extension/tree/decode.rs
new file mode 100644
index 000000000..82221b48c
--- /dev/null
+++ b/vendor/gix-index/src/extension/tree/decode.rs
@@ -0,0 +1,63 @@
+use std::convert::TryInto;
+
+use gix_hash::ObjectId;
+
+use crate::{
+    extension::Tree,
+    util::{split_at_byte_exclusive, split_at_pos},
+};
+
+/// A recursive data structure
+pub fn decode(data: &[u8], object_hash: gix_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)
+}
+
+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 num_entries: i32 = btoi::btoi(entry_count).ok()?;
+
+    let (subtree_count, data) = split_at_byte_exclusive(data, b'\n')?;
+    let subtree_count: usize = btoi::btou(subtree_count).ok()?;
+
+    let (id, mut data) = if num_entries >= 0 {
+        let (hash, data) = split_at_pos(data, hash_len)?;
+        (ObjectId::from(hash), data)
+    } else {
+        (
+            ObjectId::null(gix_hash::Kind::from_hex_len(hash_len * 2).expect("valid hex_len")),
+            data,
+        )
+    };
+
+    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;
+    }
+
+    subtrees.sort_by(|a, b| a.name.cmp(&b.name));
+    let num_trees = subtrees.len();
+    subtrees.dedup_by(|a, b| a.name == b.name);
+    if num_trees != subtrees.len() {
+        return None;
+    }
+
+    Some((
+        Tree {
+            id,
+            num_entries: num_entries.try_into().ok(),
+            name: path.into(),
+            children: subtrees,
+        },
+        data,
+    ))
+}