private function readUsageType($pointer) {
    if (false === $pointer) {
      // Deal with invalid IPs
      $usageType = self::INVALID_IP_ADDRESS;
    } elseif (0 === self::$columns[self::USAGE_TYPE][$this->type]) {
      // If the field is not suported, return accordingly
      $usageType = self::FIELD_NOT_SUPPORTED;
    } else {
      $usageType = $this->readString($pointer + self::$columns[self::USAGE_TYPE][$this->type]);
    }
    return $usageType;
  }