/* First translation - encoding of repeated characters
* The code is byte for byte pass through except that
* DLE is encoded as DLE, zero and repeated byte values
* are encoded as value, DLE, count for count >= 3.
*/
init_ncr() /*initialize getcnr() */
{
state = NOHIST;
}
int
getcnr(iob)
FILE *iob;
{
switch(state) {
case NOHIST:
/* No relevant history */
state = SENTCHAR;
return lastchar = getc_crc(iob);
case SENTCHAR:
/* Lastchar is set, need lookahead */
switch(lastchar) {
case DLE:
state = NOHIST;
return 0; /* indicates DLE was the data */
case EOF:
return EOF;
default:
for(likect = 1; (newchar = getc_crc(iob)) == lastchar && likect < 255; ++likect)
;
switch(likect) {
case 1:
return lastchar = newchar;
case 2:
/* just pass through */
state = SENDNEWC;
return lastchar;
default:
state = SENDCNT;
return DLE;
}
}
case SENDNEWC:
/* Previous sequence complete, newchar set */
state = SENTCHAR;
return lastchar = newchar;
case SENDCNT:
/* Sent DLE for repeat sequence, send count */
state = SENDNEWC;
return likect;
default:
puts("Bug - bad state\n");
exit(1);
}
}
