From: Ondřej Surý <ondrej@isc.org>
Date: Wed, 12 Aug 2026 11:00:27 +0000 (+0200)
Subject: Add dns_name_empty() to skip counting all the labels in the name
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7e350ac30d1a7372f1241d4a815bd15ecb9dc2b9;p=thirdparty%2Fbind9.git

Add dns_name_empty() to skip counting all the labels in the name

Checking whether a name is empty via dns_name_countlabels() walks the
whole name just to compare the label count with zero.  An empty name
is simply one with zero length, so add dns_name_empty() that checks
the length directly, along with a coccinelle patch that converts the
existing callers.
---

diff --git a/cocci/dns_name_empty.spatch b/cocci/dns_name_empty.spatch
new file mode 100644
index 00000000000..ae47b3326ca
--- /dev/null
+++ b/cocci/dns_name_empty.spatch
@@ -0,0 +1,23 @@
+@@
+constant ZERO =~ "^0[uUlL]*$";
+expression E;
+@@
+
+- dns_name_countlabels(E) > ZERO
++ !dns_name_empty(E)
+
+@@
+constant ZERO =~ "^0[uUlL]*$";
+expression E;
+@@
+
+- dns_name_countlabels(E) == ZERO
++ dns_name_empty(E)
+
+@@
+constant ZERO =~ "^0[uUlL]*$";
+expression E;
+@@
+
+- dns_name_countlabels(E) != ZERO
++ !dns_name_empty(E)
diff --git a/lib/dns/include/dns/name.h b/lib/dns/include/dns/name.h
index db9752fc827..60506f73e4e 100644
--- a/lib/dns/include/dns/name.h
+++ b/lib/dns/include/dns/name.h
@@ -591,6 +591,20 @@ dns_name_offsets(const dns_name_t *name, dns_offsets_t offsets);
  *	individual labels in the name
  */
 
+static inline bool
+dns_name_empty(const dns_name_t *name) {
+	REQUIRE(DNS_NAME_VALID(name));
+
+	return name->length == 0;
+}
+/*%<
+ * Return whether the name is empty.
+ *
+ * Requires:
+ * \li	'name' is a valid name
+ *
+ */
+
 static inline uint8_t
 dns_name_countlabels(const dns_name_t *name) {
 	REQUIRE(DNS_NAME_VALID(name));