if (bytesLeft == -1L || constructed) {
      throw ProtocolException("constructed octet strings not supported for DER")
    }
    return source.readByteString(bytesLeft)
  }

  fun readUtf8String(): String {
    if (bytesLeft == -1L || constructed) {
      throw ProtocolException("constructed strings not supported for DER")
    }
    return source.readUtf8(bytesLeft)
  }