random.nextBytes(maskKey!!)
      sinkBuffer.write(maskKey)

      if (length > 0) {
        val payloadStart = sinkBuffer.size
        sinkBuffer.write(payload)

        sinkBuffer.readAndWriteUnsafe(maskCursor!!)
        maskCursor.seek(payloadStart)
        toggleMask(maskCursor, maskKey)
        maskCursor.close()
      }
    } else {
      sinkBuffer.writeByte(b1)
      sinkBuffer.write(payload)

    deflaterSink.flush()

    if (deflatedBytes.endsWith(EMPTY_DEFLATE_BLOCK)) {
      val newSize = deflatedBytes.size - LAST_OCTETS_COUNT_TO_REMOVE_AFTER_DEFLATION
      deflatedBytes.readAndWriteUnsafe().use { cursor ->
        cursor.resizeBuffer(newSize)
      }
    } else {
      // Same as adding EMPTY_DEFLATE_BLOCK and then removing 4 bytes.
      deflatedBytes.writeByte(0x00)
    }

  @Throws(IOException::class)
  private fun readControlFrame() {
    if (frameLength > 0L) {
      source.readFully(controlFrameBuffer, frameLength)

      if (!isClient) {
        controlFrameBuffer.readAndWriteUnsafe(maskCursor!!)
        maskCursor.seek(0)
        toggleMask(maskCursor, maskKey!!)
        maskCursor.close()
      }
    }

    when (opcode) {
      OPCODE_CONTROL_PING -> {