path-lookup: add state_directory_generic() helper inspired by runtime_directory_generic()

src/libsystemd/sd-path/path-lookup.c

@@ -140,6 +140,30 @@ int runtime_directory_make(RuntimeScope scope, const char *subdir, char **ret_di
         return 0;
 }
 
+int state_directory_generic(RuntimeScope scope, const char *suffix, char **ret) {
+        assert(ret);
+
+        /* This does not bother with $STATE_DIRECTORY, and hence can be applied to get other service's state
+         * dir */
+
+        switch (scope) {
+
+        case RUNTIME_SCOPE_USER:
+                return xdg_user_state_dir(suffix, ret);
+
+        case RUNTIME_SCOPE_SYSTEM: {
+                char *d = path_join("/var/lib", suffix);
+                if (!d)
+                        return -ENOMEM;
+                *ret = d;
+                return 0;
+        }
+
+        default:
+                return -EINVAL;
+        }
+}
+
 static const char* const user_data_unit_paths[] = {
         "/usr/local/lib/systemd/user",
         "/usr/local/share/systemd/user",

src/libsystemd/sd-path/path-lookup.h

@@ -61,6 +61,7 @@ int config_directory_generic(RuntimeScope scope, const char *suffix, char **ret)
 int runtime_directory_generic(RuntimeScope scope, const char *suffix, char **ret);
 int runtime_directory(RuntimeScope scope, const char *fallback_suffix, char **ret);
 int runtime_directory_make(RuntimeScope scope, const char *subdir, char **ret_dir, char **ret_dir_destroy);
+int state_directory_generic(RuntimeScope scope, const char *suffix, char **ret);
 
 /* We don't treat /etc/xdg/systemd/ in these functions as the xdg base dir spec suggests because we assume
  * that is a link to /etc/systemd/ anyway. */
@@ -75,6 +76,9 @@ static inline int xdg_user_config_dir(const char *suffix, char **ret) {
 static inline int xdg_user_data_dir(const char *suffix, char **ret) {
         return sd_path_lookup(SD_PATH_USER_SHARED, suffix, ret);
 }
+static inline int xdg_user_state_dir(const char *suffix, char **ret) {
+        return sd_path_lookup(SD_PATH_USER_STATE_PRIVATE, suffix, ret);
+}
 
 bool path_is_user_data_dir(const char *path);
 bool path_is_user_config_dir(const char *path);