How transmit data in ADALM-Pluto with libiio C/C++

Question

I cannot understand how transmit data in libiio. In example https://github.com/analogdevicesinc/libiio/blob/master/examples/ad9361-iiostream.c#L248 i cannot understand which line is transmitting data. On matlab i can transmit data with function transmitRepeat or calling sdrTransmitter(txWaveForm). How can i do this in C/C++ libiio Maybe this is what making tramsit the signal? ` // Streaming devices struct iio_device* tx; struct iio_device* rx;

   // RX and TX sample counters
   size_t nrx = 0;
   size_t ntx = 0;

    // Stream configurations
    struct stream_cfg rxcfg;
    struct stream_cfg txcfg;

    // Listen to ctrl+c and IIO_ENSURE
    signal(SIGINT, handle_sig);

    // RX stream config
    rxcfg.bw_hz = MHZ(2);   // 2 MHz rf bandwidth
    rxcfg.fs_hz = MHZ(2.5);   // 2.5 MS/s rx sample rate
    rxcfg.lo_hz = GHZ(2.5); // 2.5 GHz rf frequency
    rxcfg.rfport = "A_BALANCED"; // port A (select for rf freq.)

    // TX stream config
    txcfg.bw_hz = MHZ(1.5); // 1.5 MHz rf bandwidth
    txcfg.fs_hz = MHZ(2.5);   // 2.5 MS/s tx sample rate
    txcfg.lo_hz = GHZ(2.5); // 2.5 GHz rf frequency
    txcfg.rfport = "A"; // port A (select for rf freq.)

    printf("* Acquiring IIO context\n");
    ctx = iio_create_context_from_uri("ip:192.168.2.1");
    IIO_ENSURE(iio_context_get_devices_count(ctx) > 0 && "No devices");

    printf("* Acquiring AD9361 streaming devices\n");
    IIO_ENSURE(get_ad9361_stream_dev(TX, &tx) && "No tx dev found");
    IIO_ENSURE(get_ad9361_stream_dev(RX, &rx) && "No rx dev found");

    printf("* Configuring AD9361 for streaming\n");
    IIO_ENSURE(cfg_ad9361_streaming_ch(&rxcfg, RX, 0) && "RX port 0 not found");
    IIO_ENSURE(cfg_ad9361_streaming_ch(&txcfg, TX, 0) && "TX port 0 not found");

    printf("* Initializing AD9361 IIO streaming channels\n");
    IIO_ENSURE(get_ad9361_stream_ch(RX, rx, 0, &rx0_i) && "RX chan i not found");
    IIO_ENSURE(get_ad9361_stream_ch(RX, rx, 1, &rx0_q) && "RX chan q not found");
    IIO_ENSURE(get_ad9361_stream_ch(TX, tx, 0, &tx0_i) && "TX chan i not found");
    IIO_ENSURE(get_ad9361_stream_ch(TX, tx, 1, &tx0_q) && "TX chan q not found");

    printf("* Enabling IIO streaming channels\n");
    iio_channel_enable(rx0_i);
    iio_channel_enable(rx0_q);
    iio_channel_enable(tx0_i);
    iio_channel_enable(tx0_q);

    printf("* Creating non-cyclic IIO buffers with 1 MiS\n");
    rxbuf = iio_device_create_buffer(rx, 1024 * 1024, false);
    if (!rxbuf) {
        perror("Could not create RX buffer");
        shutdown();
    }
    txbuf = iio_device_create_buffer(tx, 1024 * 1024, false);
    if (!txbuf) {
        perror("Could not create TX buffer");
        shutdown();
    }

    printf("* Starting IO streaming (press CTRL+C to cancel)\n");
    while (!stop)
    {
        ssize_t nbytes_rx, nbytes_tx;
        char* p_dat, * p_end;
        ptrdiff_t p_inc;

        // Schedule TX buffer
        nbytes_tx = iio_buffer_push(txbuf);
        if (nbytes_tx < 0) { printf("Error pushing buf %d\n", (int)nbytes_tx); shutdown(); }

        // Refill RX buffer
        nbytes_rx = iio_buffer_refill(rxbuf);
        if (nbytes_rx < 0) { printf("Error refilling buf %d\n", (int)nbytes_rx); shutdown(); }

        // READ: Get pointers to RX buf and read IQ from RX buf port 0
        p_inc = iio_buffer_step(rxbuf);
        p_end = iio_buffer_end(rxbuf);
        for (p_dat = (char*)iio_buffer_first(rxbuf, rx0_i); p_dat < p_end; p_dat += p_inc) {
            // Example: swap I and Q
            const int16_t i = ((int16_t*)p_dat)[0]; // Real (I)
            const int16_t q = ((int16_t*)p_dat)[1]; // Imag (Q)
            ((int16_t*)p_dat)[0] = q;
            ((int16_t*)p_dat)[1] = i;
        }

        // WRITE: Get pointers to TX buf and write IQ to TX buf port 0
        p_inc = iio_buffer_step(txbuf);
        p_end = iio_buffer_end(txbuf);
        for (p_dat = (char*)iio_buffer_first(txbuf, tx0_i); p_dat < p_end; p_dat += p_inc) {
            // Example: fill with zeros
            // 12-bit sample needs to be MSB aligned so shift by 4
            // https://wiki.analog.com/resources/eval/user-guides/ad-fmcomms2-ebz/software/basic_iq_datafiles#binary_format
            ((int16_t*)p_dat)[0] = 0 << 4; // Real (I)
            ((int16_t*)p_dat)[1] = 0 << 4; // Imag (Q)
        }

        // Sample counter increment and status output
        nrx += nbytes_rx / iio_device_get_sample_size(rx);
        ntx += nbytes_tx / iio_device_get_sample_size(tx);
        //printf(nbytes_tx);
        printf("\tRX %8.2f MSmp, TX %8.2f MSmp\n", nrx/ 1e6, ntx / 1e6);
    }

    shutdown();

    return 0;
}`