Re: [Discuss-gnuradio] Liquid DSP Flexframe and GNU Radio

Hey!

As fas as I can tell, you don't check if the output buffer can actually
take that many samples. Thus "you end up in the middle of invalid
memory". At least that's what I guess from the code I can see. You need
to ensure that 'noutput_items' always holds a value greater than your
final 'total_items'.

Cheers
Johannes

On 26.07.2016 03:13, Vanhoy, Garrett M - (gvanhoy) wrote:
> Hello,
>
>
> I have sent this to the list once before, but I did not see it show up
> on the index so I am assuming it did not work after waiting some time.
>
>
> I am attempting to embed the liquid DSP
> <https://github.com/jgaeddert/liquid-dsp> flexframe protocol in a custom
> GNU Radio block. I am doing this by extending the out-of-tree module
> that Tom Rondeau recently worked on
> <https://github.com/trondeau/gr-liquiddsp>. I am writing a block that
> embeds the flexframegen and another that embeds a flexframesync. Since
> these blocks tend to produce a varying amount of symbols depending on
> the coding scheme or modulation, I wrote it as a general block. You can
> see the current version of the code at my own fork
> <https://github.com/gvanhoy/gr-liquiddsp>.
>
>
> I am currently having trouble with the generator and occasionally the
> sync block as well. However, for the generator, I am getting a return
> code -11 (I assume a seg fault) when I attempt to copy a generated frame
> to the out buffer and run this in GNURadioCompanion. This often happens
> after attempting to copy ~16000 gr_complex items to the outbuffer. Is
> there a problems with that amount? Here is my work function code:
>
>
> {
> unsigned int buf_len = 1000;
> unsigned int payload_len = 4096;
> unsigned char header[14]; // Liquid hardcodes this as the
> length for the header
> unsigned char payload[4096];
>
> unsigned char *in = (unsigned char *) input_items[0];
> unsigned char *inbuf = in;
> gr_complex *out = (gr_complex *) output_items[0];
> gr_complex *outbuf = (gr_complex *)
> malloc(buf_len*sizeof(gr_complex));
> gr_complex *front = out;
> int byte_count = 0;
>
> unsigned char frame_count;
> unsigned int total_items = 0;
> int frame_complete = 0;
>
> // Make header
> for(int i = 1; i < 14; i++) header[i] = i;
> while(byte_count < ((int) ninput_items[0]) - payload_len) {
> header[0] = frame_count;
> frame_count > 255 ? frame_count = 0 : frame_count++;
> memcpy(payload, inbuf, payload_len);
> inbuf += payload_len;
> byte_count += payload_len;
> // Assemble the frame
> while (!flexframegen_is_assembled(d_fg)) {
> flexframegen_assemble(d_fg, header, payload, payload_len);
> }
>
> // Make the frame in blocks
> frame_complete = 0;
> while (!frame_complete){
> frame_complete = flexframegen_write_samples(d_fg,
> outbuf, buf_len);
> memcpy(front, outbuf, buf_len*sizeof(gr_complex));
> front += buf_len;
> total_items += buf_len;
> }
>
> // Get frame length
> }
>
> free(outbuf);
> consume_each (total_items);
>
> // Tell runtime system how many output items we produced.
> return total_items;
> }
>
>
> Any ideas? Thanks for any help.
>
>
>
>
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> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
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>

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