namedb: make the API constant

src/common/namedb/namedb_lmdb.c

@@ -325,9 +325,9 @@ static void iter_finish(knot_iter_t *iter)
 	mdb_cursor_close(cursor);
 }
 
-struct namedb_api *namedb_lmdb_api(void)
+const struct namedb_api *namedb_lmdb_api(void)
 {
-	static struct namedb_api api = {
+	static const struct namedb_api api = {
 		"lmdb",
 		init, deinit,
 		txn_begin, txn_commit, txn_abort,
@@ -342,7 +342,7 @@ struct namedb_api *namedb_lmdb_api(void)
 
 #include <stdlib.h>
 
-struct namedb_api *namedb_lmdb_api(void)
+const struct namedb_api *namedb_lmdb_api(void)
 {
 	return NULL;
 }

src/common/namedb/namedb_lmdb.h

@@ -18,4 +18,4 @@
 
 #include "common/namedb/namedb.h"
 
-struct namedb_api *namedb_lmdb_api(void);
+const struct namedb_api *namedb_lmdb_api(void);

src/common/namedb/namedb_trie.c

@@ -126,9 +126,9 @@ static void iter_finish(knot_iter_t *iter)
 	hattrie_iter_free((hattrie_iter_t *)iter);
 }
 
-struct namedb_api *namedb_trie_api(void)
+const struct namedb_api *namedb_trie_api(void)
 {
-	static struct namedb_api api = {
+	static const struct namedb_api api = {
 		"hattrie",
 		init, deinit,
 		txn_begin, txn_commit, txn_abort,

src/common/namedb/namedb_trie.h

@@ -18,4 +18,4 @@
 
 #include "common/namedb/namedb.h"
 
-struct namedb_api *namedb_trie_api(void);
+const struct namedb_api *namedb_trie_api(void);

tests/namedb.c

@@ -48,7 +48,7 @@ static char *str_key_rand(size_t len, mm_ctx_t *pool)
 #include "common-knot/array-sort.h"
 
 static void namedb_test_set(unsigned nkeys, char **keys, char *dbid,
-                            struct namedb_api *api, mm_ctx_t *pool)
+                            const struct namedb_api *api, mm_ctx_t *pool)
 {
 	if (api == NULL) {
 		skip("API not compiled in");