+struct expand_data {
+ unsigned char sha1[20];
+ enum object_type type;
+ unsigned long size;
+
+ /*
+ * If mark_query is true, we do not expand anything, but rather
+ * just mark the object_info with items we wish to query.
+ */
+ int mark_query;
+
+ /*
+ * After a mark_query run, this object_info is set up to be
+ * passed to sha1_object_info_extended. It will point to the data
+ * elements above, so you can retrieve the response from there.
+ */
+ struct object_info info;
+};
+
+static int is_atom(const char *atom, const char *s, int slen)
+{
+ int alen = strlen(atom);
+ return alen == slen && !memcmp(atom, s, alen);
+}
+
+static void expand_atom(struct strbuf *sb, const char *atom, int len,
+ void *vdata)
+{
+ struct expand_data *data = vdata;
+
+ if (is_atom("objectname", atom, len)) {
+ if (!data->mark_query)
+ strbuf_addstr(sb, sha1_to_hex(data->sha1));
+ } else if (is_atom("objecttype", atom, len)) {
+ if (!data->mark_query)
+ strbuf_addstr(sb, typename(data->type));
+ } else if (is_atom("objectsize", atom, len)) {
+ if (data->mark_query)
+ data->info.sizep = &data->size;
+ else
+ strbuf_addf(sb, "%lu", data->size);
+ } else
+ die("unknown format element: %.*s", len, atom);
+}
+
+static size_t expand_format(struct strbuf *sb, const char *start, void *data)
+{
+ const char *end;
+
+ if (*start != '(')
+ return 0;
+ end = strchr(start + 1, ')');
+ if (!end)
+ die("format element '%s' does not end in ')'", start);
+
+ expand_atom(sb, start + 1, end - start - 1, data);
+
+ return end - start + 1;
+}
+