while (sendBuffer.size >= EMIT_BUFFER_SIZE) {
        emitFrame(false)
      }
    }

    /**
     * Emit a single data frame to the connection. The frame's size be limited by this stream's
     * write window. This method will block until the write window is nonempty.
     */
    @Throws(IOException::class)
    private fun emitFrame(outFinishedOnLastFrame: Boolean) {
      val toWrite: Long