From 0aca3bcfe7aaf83b22bdebceaf0209fa393d0c6b Mon Sep 17 00:00:00 2001
From: Runxi Yu <me@runxiyu.org>
Date: Sun, 14 Sep 2025 03:24:22 +0800
Subject: [PATCH] Primitive tree-parsing function

---
 git/obj_tree.ha | 40 ++++++++++++++++++++++++++++++++++++++++

diff --git a/git/obj_tree.ha b/git/obj_tree.ha
index 4082b28e4a028dd1559574be571d14daf5b76a0a..58c3d41e50aa03121cf67230a7fa4e518c208381 100644
--- a/git/obj_tree.ha
+++ b/git/obj_tree.ha
@@ -1,3 +1,9 @@
+use bytes;
+use crypto::sha256;
+use errors;
+use strconv;
+use strings;
+
 export type tree = struct {
 	oid: oid,
 	entries: []tree_entry,
@@ -17,3 +23,37 @@ };
 export fn tree_entry_finish(te: tree_entry) void = {
 	free(te.name);
 };
+
+export fn parse_tree(id: oid, body: []u8) (tree | errors::invalid | strconv::invalid | strconv::overflow | nomem) = {
+	let entries: []tree_entry = [];
+	let i = 0z;
+
+	for (i < len(body)) {
+		const sp = match (bytes::index(body[i..], ' ')) {
+		case let j: size => yield j;
+		case void => return errors::invalid;
+		};
+		const mode_b = body[i .. i+sp];
+		i += sp + 1z;
+
+		const nul = match (bytes::index(body[i..], 0u8)) {
+		case let j: size => yield j;
+		case void => return errors::invalid;
+		};
+		const name_b = body[i .. i+nul];
+		i += nul + 1z;
+
+		if (i + sha256::SZ > len(body)) return errors::invalid;
+		let child: oid = [0...];
+		child[..] = body[i .. i+sha256::SZ];
+		i += sha256::SZ;
+
+		const mode_s = strings::fromutf8_unsafe(mode_b);
+		const mode = strconv::stou32(mode_s, strconv::base::OCT)?;
+
+		const name = name_b[..];
+		append(entries, tree_entry { mode = mode, name = name, oid = child })!;
+	};
+
+	return tree { oid = id, entries = entries };
+};

-- 
2.48.1