writeBytesTotal += toWrite
        outFinished = outFinishedOnLastFrame && toWrite == sendBuffer.size
      }

      writeTimeout.enter()
      try {
        connection.writeData(id, outFinished, sendBuffer, toWrite)
      } finally {
        writeTimeout.exitAndThrowIfTimedOut()
      }
    }

    @Throws(IOException::class)
    override fun flush() {
      lock.assertNotHeld()