• Dump contents in raw packet data (packets are in ASCII format) in C

    ShikhaTan Member August 25, 2015 at 4:01 pm

    Dump contents in raw packet data (packets are in ASCII format).
    I need raw packet data (packets are in ascii format). I’m limited in size because I’m using 3rd party lib print utility that redirect the logs to an equipment

    #7532
  • Ganesh Member August 25, 2015 at 4:02 pm

    Would calling your print utility in a loop until all the packed is dumped be be an option or is there an issue with that? E.g. like

    unsigned int written = 0;

for (written = 0; i < packet_size - packet_size % 90; written += 90) {

  // write 90 bytes
  log_3rd_party(packet_buffer + written, 90);
}

// log the remainder
log_3rd_party(packet_buffer + written, packet_size % 90);
    #7533
  • ShikhaTan Member August 25, 2015 at 4:02 pm

    If log_3rd_party does not allow to pass a length, so we may need to copy to a temporary buffer.

    unsigned int written = 0;
char buf[92];

for (written = 0; i < packet_size - packet_size % 90; written += 90) {

  // write 90 bytes
  memcpy(buf,packet_buffer + written, 90); // could also use 'snprintf()', won't terminate iether
  buf[91] = '\0'; // zero-terminate buffer
  log_3rd_party(buf);
}

// log the remainder
unsigned remainder =  packet_size % 90;
memcpy(buf,packet_buffer + written,  remainder); // could also use 'snprintf()', won't terminate iether
buf[ remainder + 1] = '\0'; // zero-terminate buffer
log_3rd_party(buf);
    #7534
  • ShikhaTan Member August 25, 2015 at 4:14 pm

    A couple of thoughts come to mind….

    Are you sure that the buffer is longer than the data? It could be a simple buffer overrun.

    Do you need to flush the output file? It’s possible that the 3rd party I/O package can’t handle that much data that fast.

    #7536
  • Ganesh Member August 25, 2015 at 4:19 pm 
    // write 90 bytes
  memcpy(buf,packet_buffer + written, 90); // could also use 'snprintf()', won't terminate iether
  buf[91] = '\0'; // zero-terminate buffer

    The buffer terminates at buf[91] what means it is the 92th byte. so after 90 characters the buffer contains 1 byte with random contents. also if the print function expects a 90-byte buffer, it is probably too much to pass 92 bytes since it might write beyond buffer boundaries in the print function by 1 or two bytes.

    so the code should be

    char buf[90] = { '\0' };  // initialize the buffer
for (written = 0; written < packet_size - remainder; written += 89) {

 // copy 89 bytes (or less at end)
  int ncopy = min(89, packet_size-remainder-written);
  memcpy(buf, packet_buffer + written, ncopy); 
  buf[ncopy] = '\0'; // zero-terminate buffer in 90th byte (is buf[89])
    #7537
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