lib: Add str_list_add_printf()

Build up execv argument lists

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

lib/util/tests/strlist.c

@@ -493,10 +493,32 @@ static bool test_list_append_const(struct torture_context *tctx)
 	return true;
 }
 
+static bool test_list_add_printf_NULL(struct torture_context *tctx)
+{
+	char **list = NULL;
+	str_list_add_printf(&list, "x=%d", 1);
+	torture_assert(tctx, list==NULL, "str_list_add_printf must keep NULL");
+	return true;
+}
+
+static bool test_list_add_printf(struct torture_context *tctx)
+{
+	const char *list2[] = { "foo", "bar=baz", NULL };
+	char **list = str_list_make_empty(tctx);
+	str_list_add_printf(&list, "foo");
+	str_list_add_printf(&list, "bar=%s", "baz");
+	torture_assert(
+		tctx,
+		str_list_equal((const char * const *)list, list2),
+		"str_list_add_printf failed");
+	TALLOC_FREE(list);
+	return true;
+}
+
 struct torture_suite *torture_local_util_strlist(TALLOC_CTX *mem_ctx)
 {
 	struct torture_suite *suite = torture_suite_create(mem_ctx, "strlist");
-	int i;
+	size_t i;
 
 	for (i = 0; i < ARRAY_SIZE(test_lists_shell_strings); i++) {
 		char *name;
@@ -528,6 +550,9 @@ struct torture_suite *torture_local_util_strlist(TALLOC_CTX *mem_ctx)
 	torture_suite_add_simple_test(suite, "list_unique_2", test_list_unique_2);
 	torture_suite_add_simple_test(suite, "list_append", test_list_append);
 	torture_suite_add_simple_test(suite, "list_append_const", test_list_append_const);
-
+	torture_suite_add_simple_test(
+		suite, "list_add_printf_NULL", test_list_add_printf_NULL);
+	torture_suite_add_simple_test(
+		suite, "list_add_printf", test_list_add_printf);
 	return suite;
 }

lib/util/util_strlist.c

@@ -299,6 +299,57 @@ _PUBLIC_ const char **str_list_add(const char **list, const char *s)
 	return ret;
 }
 
+/**
+ * @brief Extend a talloc'ed string list with a printf'ed string
+ *
+ * str_list_add_printf() does nothing if *plist is NULL and it sets
+ * *plist to NULL on failure. It is designed to avoid intermediate
+ * NULL checks:
+ *
+ *     argv = str_list_make_empty(ctx);
+ *     str_list_add_printf(&argv, "smbstatus");
+ *     str_list_add_printf(&argv, "--configfile=%s", config);
+ *     if (argv == NULL) {
+ *        goto nomem;
+ *     }
+ *
+ * @param[in,out] plist The talloc'ed list to extend
+ * @param[in] fmt The format string
+ */
+void str_list_add_printf(char ***plist, const char *fmt, ...)
+{
+	char **list = *plist;
+	size_t len;
+	char **tmp = NULL;
+	va_list ap;
+
+	if (list == NULL) {
+		return;
+	}
+	len = str_list_length((const char * const *)list);
+
+	tmp = talloc_realloc(NULL, list, char *, len+2);
+	if (tmp == NULL) {
+		goto fail;
+	}
+	list = tmp;
+	list[len+1] = NULL;
+
+	va_start(ap, fmt);
+	list[len] = talloc_vasprintf(list, fmt, ap);
+	va_end(ap);
+
+	if (list[len] == NULL) {
+		goto fail;
+	}
+	*plist = list;
+
+	return;
+fail:
+	TALLOC_FREE(list);
+	*plist = NULL;
+}
+
 /**
   remove an entry from a string list
 */

lib/util/util_strlist.h

@@ -87,6 +87,12 @@ bool str_list_equal(const char * const *list1,
 */
 const char **str_list_add(const char **list, const char *s);
 
+/*
+ * Extend a list with a printf'ed string
+ */
+void str_list_add_printf(char ***plist, const char *fmt, ...)
+	PRINTF_ATTRIBUTE(2,3);
+
 /**
   remove an entry from a string list
 */