public function searchOrigDir(File $cacheDir) {
        foreach ($this->autoDirPathMap as $entry_set) {
            $orig_dir = $entry_set[0];
            $cache_dir = $entry_set[1];
            if ($cacheDir->getAbsolutePath() === $cache_dir->getAbsolutePath()) {
                return $orig_dir;
            }
        }
        return null;
    }