/* Sends the contents of `fname` to `device`, expecting every sent byte to be
* echoed back verbatim. Compare every echoed byte with the one sent and bail
* out if a mismatch is detected. When the whole file is sent, push a null char
* to indicate EOF to the receiving end.
*
* It is recommended that you send contents that has gone through `ttysafe`.
*/
int main(int argc, char **argv)
{
if (argc != 3) {
fprintf(stderr, "Usage: ./pingpong device fname\n");
return 1;
}
FILE *fp = fopen(argv[2], "r");
if (!fp) {
fprintf(stderr, "Can't open %s.\n", argv[2]);
return 1;
}
int fd = open(argv[1], O_RDWR|O_NOCTTY|O_NONBLOCK);
printf("Press a key...\n");
getchar();
unsigned char c;
// empty the recv buffer
while (read(fd, &c, 1) == 1) usleep(1000);
int returncode = 0;
while (fread(&c, 1, 1, fp)) {
putchar('.');
fflush(stdout);
write(fd, &c, 1);
usleep(1000); // let it breathe
unsigned char c2;
while (read(fd, &c2, 1) != 1); // read echo
if (c != c2) {
// mismatch!
unsigned int pos = ftell(fp);
fprintf(stderr, "Mismatch at byte %d! %d != %d.\n", pos, c, c2);
returncode = 1;
break;
}
}
// To close the receiving loop on the other side, we send a straight null
c = 0;
write(fd, &c, 1);
printf("Done!\n");
fclose(fp);
return returncode;
}
