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hdlcgen.c

#define FAST_HDLC_NEED_TABLES
#include "fasthdlc.h"
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>

#define RANDOM "/dev/urandom"             /* Not genuinely random */
/* #define RANDOM "/dev/random" */        /* Quite genuinely random */

int myread(int fd, char *buf, int len)
{
      int sofar;
      int res;
      sofar = 0;
      while(sofar < len) {
            res = read(fd, buf + sofar, len - sofar);
            if (res < 0)
                  return res;
            sofar += res;
      }
      return sofar;
}

int main(int argc, char *argv[])
{
      unsigned char buf[1024];
      unsigned char outbuf[2048];
      int res;
      int randin;
      int randout;
      int hdlcout;
      int cnt;
      int hdlccnt;
      int x;
      int flags;
      struct fasthdlc_state transmitter;
      
      fasthdlc_precalc();
      
      fasthdlc_init(&transmitter);
      
      randin = open(RANDOM, O_RDONLY);
      if (randin < 0) {
            fprintf(stderr, "Unable to open %s: %s\n", RANDOM, strerror(errno));
            exit(1);
      }
      randout = open("random.raw", O_WRONLY|O_TRUNC|O_CREAT, 0666);
      if (randout < 0) {
            fprintf(stderr, "Unable to open random.raw: %s\n", strerror(errno));
            exit(1);
      }
      hdlcout = open("random.hdlc", O_WRONLY|O_TRUNC|O_CREAT, 0666);
      if (hdlcout < 0) {
            fprintf(stderr, "Unable to open random.hdlc: %s\n", strerror(errno));
            exit(1);
      }
      for (;;) {
            cnt = (rand() % 256) + 4;     /* Read a pseudo-random amount of stuff */
            res = myread(randin, buf, cnt);
            if (res != cnt) {
                  fprintf(stderr, "Tried to read %d bytes, but read %d instead\n", cnt, res);
                  exit(1);
            }
            res = write(randout, buf, cnt);
            if (res != cnt) {
                  fprintf(stderr, "Tried to write %d bytes, but wrote %d instead\n", cnt, res);
                  exit(1);
            }
            /* HDLC encode */
            hdlccnt = 0;
            /* Start with a flag */
            fasthdlc_tx_frame(&transmitter);
            if (transmitter.bits >= 8)
                  outbuf[hdlccnt++] = fasthdlc_tx_run(&transmitter);
            for (x=0;x<cnt;x++) {
                  res = fasthdlc_tx_load(&transmitter, buf[x]);
                  if (res < 0) {
                        fprintf(stderr, "Unable to load byte :(\n");
                        exit(1);
                  }
                  while(transmitter.bits >= 8)  {
                        outbuf[hdlccnt++] = fasthdlc_tx_run(&transmitter);
                  }
            }
            flags = (rand() % 4);
            for (x=0;x<flags;x++) {
                  if (transmitter.bits < 8)
                        fasthdlc_tx_frame(&transmitter);
                  else
                        fprintf(stderr, "Huh?  Don't need a frame?\n");
                  outbuf[hdlccnt++] = fasthdlc_tx_run(&transmitter);
            }
            if (argc > 1)
                  printf("Encoded %d byte message with %d bytes of HDLC and %d extra flags\n", cnt, hdlccnt, flags);
            res = write(hdlcout, outbuf, hdlccnt);
            if (res != hdlccnt) {
                  fprintf(stderr, "Tried to write %d HDLC bytes, but wrote %d instead\n", cnt, res);
                  exit(1);
            }
            
      }
}

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