anchor.diff:    }
   
     /**
  +   * Constructs a uuid combining the current date and a random integer.
  +   */
  +  String _generateUuidString() {
  +    int millisecondsSinceEpoch = new DateTime.now().millisecondsSinceEpoch;
  +    int random = new Random().nextInt(0x3fffffff);
  +    return '$millisecondsSinceEpoch$random';
  +  }
  +
  +  /**
      * Perform log files rolling.
      *
      * Rename existing files with names `[path].(x)` to `[path].(x+1)`.
  
positive.code:    * Read the UUID from disk, generating and storing a new one if necessary.
     */
    String _readUuid(InstrumentationService service) {
      File uuidFile = new File(PhysicalResourceProvider.INSTANCE
          .getStateLocation('.instrumentation')
          .getChild('uuid.txt')
          .path);
      try {
        if (uuidFile.existsSync()) {
          String uuid = uuidFile.readAsStringSync();
  
negative.code:     } catch (exception, stackTrace) {
        service.logPriorityException(exception, stackTrace);
      }
      String uuid = _generateUuidString();
      try {
        uuidFile.parent.createSync(recursive: true);
        uuidFile.writeAsStringSync(uuid);
  