Method handleAckByte

app/src/IO/FileTransmission/XMODEM.cpp:120–170

* @brief Reacts to a byte received while waiting for ACK/NAK after a data block. * Returns false when processing must stop because the transfer ended. */

 *        Returns false when processing must stop because the transfer ended.
 */
bool IO::Protocols::XMODEM::handleAckByte(quint8 ch)
{
  if (ch == kACK) {
    m_timeoutTimer.stop();
    m_retryCount  = 0;
    m_blockNumber = static_cast<quint8>((m_blockNumber + 1) & 0xFF);
    m_state       = State::SendingBlocks;

    if (m_file.atEnd())
      sendEOT();
    else
      sendBlock();

    return true;
  }

  if (ch == kNAK) {
    m_timeoutTimer.stop();
    ++m_retryCount;
    if (m_retryCount >= m_maxRetries) {
      sendCancel();
      resetState();
      Q_EMIT statusMessage(tr("Too many retries, transfer aborted"));
      Q_EMIT finished(false, tr("Maximum retries exceeded"));
      return false;
    }

    Q_EMIT statusMessage(tr("NAK received, retrying block %1 (%2/%3)")
                           .arg(m_blockNumber)
                           .arg(m_retryCount)
                           .arg(m_maxRetries));

    m_bytesSent = qMax<qint64>(0, m_bytesSent - m_lastBlockBytes);
    if (!m_file.seek(m_lastBlockStart)) [[unlikely]] {
      m_file.close();
      Q_EMIT finished(false, tr("Failed to seek in file"));
      return false;
    }
    sendBlock();
    return true;
  }

  if (ch == kCAN) {
    m_timeoutTimer.stop();
    resetState();
    Q_EMIT statusMessage(tr("Transfer cancelled by receiver"));
    Q_EMIT finished(false, tr("Receiver cancelled the transfer"));
  }

  return true;
}

/**
 * @brief Reacts to a byte received while waiting for ACK after EOT.