fun readLine(): String {
    val line = source.readUtf8LineStrict(headerLimit)
    headerLimit -= line.length.toLong()
    return line
  }

  /** Reads headers or trailers. */
  fun readHeaders(): Headers {
    val result = Headers.Builder()
    while (true) {
      val line = readLine()
      if (line.isEmpty()) break
      result.addLenient(line)
    }
    return result.build()
  }

      throw IOException("Expected a SETTINGS frame but was ${formattedType(type)}")
    }

    when (type) {
      TYPE_DATA -> readData(handler, length, flags, streamId)
      TYPE_HEADERS -> readHeaders(handler, length, flags, streamId)
      TYPE_PRIORITY -> readPriority(handler, length, flags, streamId)
      TYPE_RST_STREAM -> readRstStream(handler, length, flags, streamId)

      /**
       * Read `byteCount` bytes of headers from the source stream. This implementation does not
       * propagate the never indexed flag of a header.
       */
      @Throws(IOException::class)
      fun readHeaders() {
        while (!source.exhausted()) {
          val b = source.readByte() and 0xff
          when {
            b == 0x80 -> {
              // 10000000
              throw IOException("index == 0")