utils: add lxc_append_string()

lxc_append_string() appends strings without separator. This is mostly useful
for reading in whole files line-by-line.

Signed-off-by: Christian Brauner <christian.brauner@canonical.com>

src/lxc/utils.c

@@ -1930,3 +1930,37 @@ bool task_blocking_signal(pid_t pid, int signal)
 	fclose(f);
 	return bret;
 }
+
+static int lxc_append_null_to_list(void ***list)
+{
+	int newentry = 0;
+	void **tmp;
+
+	if (*list)
+		for (; (*list)[newentry]; newentry++) {
+			;
+		}
+
+	tmp = realloc(*list, (newentry + 2) * sizeof(void **));
+	if (!tmp)
+		return -1;
+
+	*list = tmp;
+	(*list)[newentry + 1] = NULL;
+
+	return newentry;
+}
+
+int lxc_append_string(char ***list, char *entry)
+{
+	int newentry = lxc_append_null_to_list((void ***)list);
+	char *copy;
+
+	copy = strdup(entry);
+	if (!copy)
+		return -1;
+
+	(*list)[newentry] = copy;
+
+	return 0;
+}

src/lxc/utils.h

@@ -258,6 +258,8 @@ extern char *lxc_append_paths(const char *first, const char *second);
 extern bool lxc_string_in_list(const char *needle, const char *haystack, char sep);
 extern char **lxc_string_split(const char *string, char sep);
 extern char **lxc_string_split_and_trim(const char *string, char sep);
+/* Append string to NULL-terminated string array. */
+extern int lxc_append_string(char ***list, char *entry);
 
 /* some simple array manipulation utilities */
 typedef void (*lxc_free_fn)(void *);