cbuf: CharArray,
      off: Int,
      len: Int,
    ): Int {
      if (closed) throw IOException("Stream closed")

      val finalDelegate =
        delegate ?: InputStreamReader(
          source.inputStream(),
          source.readBomAsCharset(charset),
        ).also {
          delegate = it
        }
      return finalDelegate.read(cbuf, off, len)
    }