static int fixerr(msgblk_t * blk, const unsigned short crc, int *pr, int pn)
{
int i;
if (pn > 0) {
for (i = 0; i < 8; i++) {
if (fixerr
(blk, crc ^ syndrom[i + 8 * (blk->len - *pr + 1)],
pr + 1, pn - 1)) {
blk->txt[*pr] ^= (1 << i);
return 1;
}
}
return 0;
} else {
if (crc == 0)
return 1;
for (i = 0; i < 2 * 8; i++)
if (syndrom[i] == crc) {
return 1;
}
return 0;
}
}
static void *blk_thread(void *arg)
{
do {
msgblk_t *blk;
int i, pn;
unsigned short crc;
int pr[MAXPERR];
pthread_mutex_lock(&blkmtx);
while (blkq_e == NULL)
pthread_cond_wait(&blkwcd, &blkmtx);
blk = blkq_e;
blkq_e = blk->prev;
if (blkq_e == NULL)
blkq_s = NULL;
pthread_mutex_unlock(&blkmtx);
if (blk->len < 13) {
if (verbose)
fprintf(stderr, "#%d too short\n",
blk->chn + 1);
free(blk);
continue;
}
/* force STX/ETX */
blk->txt[12] &= (ETX | STX);
blk->txt[12] |= (ETX & STX);
/* parity check */
pn = 0;
for (i = 0; i < blk->len; i++) {
if ((numbits[blk->txt[i]] & 1) == 0) {
if (pn < MAXPERR) {
pr[pn] = i;
}
pn++;
}
}
if (pn > MAXPERR) {
if (verbose)
fprintf(stderr,
"#%d too many parity errors: %d\n",
blk->chn + 1, pn);
free(blk);
continue;
}
if (pn > 0 && verbose)
fprintf(stderr, "#%d parity error(s): %d\n",
blk->chn + 1, pn);
blk->err = pn;
/* crc check */
crc = 0;
for (i = 0; i < blk->len; i++) {
update_crc(crc, blk->txt[i]);
}
update_crc(crc, blk->crc[0]);
update_crc(crc, blk->crc[1]);
if (crc && verbose)
fprintf(stderr, "#%d crc error\n", blk->chn + 1);
/* try to fix error */
if (fixerr(blk, crc, pr, pn) == 0) {
if (verbose)
fprintf(stderr, "#%d not able to fix errors\n",
blk->chn + 1);
free(blk);
continue;
}
/* redo parity checking and removing */
pn = 0;
for (i = 0; i < blk->len; i++) {
if ((numbits[blk->txt[i]] & 1) == 0) {
pn++;
}
blk->txt[i] &= 0x7f;
}
if (pn) {
fprintf(stderr, "#%d parity check problem\n",
blk->chn + 1);
free(blk);
continue;
}
if (prev_t == blk->t &&
prev_crc[0] == blk->crc[0] && prev_crc[1] == blk->crc[1]) {
if (verbose)
fprintf(stderr, "#%d duplicate %d\n",
blk->chn + 1, blk->lvl);
free(blk);
continue;
}
prev_t = blk->t;
prev_crc[0] = blk->crc[0];
prev_crc[1] = blk->crc[1];
outputmsg(blk);
free(blk);
} while (1);
return NULL;
}
static void * blk_thread(void *arg)
{
do {
msgblk_t *blk;
acarsmsg_t msg;
int i,k,pn;
unsigned short crc;
pthread_mutex_lock(&blkmtx);
while(blkq_e==NULL) pthread_cond_wait(&blkwcd,&blkmtx);
blk=blkq_e;
blkq_e=blk->prev;
if(blkq_e==NULL) blkq_s=NULL;
pthread_mutex_unlock(&blkmtx);
if(blk==NULL) return;
if(blk->len<13) {
if(verbose) fprintf(stderr,"#%d too short\n",blk->chn+1);
free(blk);
continue;
}
/* force STX/ETX */
blk->txt[12]&=(ETX|STX);
blk->txt[12]|=(ETX&STX);
msg.err=0;
/* parity check */
pn=0;
for(i=0;i<blk->len;i++) {
if((numbits[blk->txt[i]]&1)==0) {
pn++;
}
}
if(pn>1) {
if(verbose) fprintf(stderr,"#%d too much parity error : %d\n",blk->chn+1,pn);
free(blk);
continue;
}
/* crc check */
crc=0;
for(i=0;i<blk->len;i++) {
update_crc(crc,blk->txt[i]);
}
update_crc(crc,blk->crc[0]);
update_crc(crc,blk->crc[1]);
/* try to fix errors */
if(crc!=0) {
int i,k,fx;
if(verbose) fprintf(stderr,"#%d CRC error, try to recover 1 error\n",blk->chn+1);
fx=0;
for(i=0;i<242*8;i++)
if(oneerr[i]==crc) {
fixerr(blk,i/8,1<<(i%8));
fx=1;
msg.err=1;
break;
}
if(fx==0 && pn==0 && blk->len<142) {
int i,k,l;
unsigned char u,v;
unsigned short n=0;
if(verbose) fprintf(stderr,"#%d CRC error, try to recover 2 close errors\n",blk->chn+1);
for(k=1,v=2;k<8;k++,v<<=1) {
for(l=0,u=1;l<k;l++,u<<=1) {
if(twoerr[n]==crc) {
fixerr(blk,0,u|v);
fx=1;
msg.err=2;
break;
}
n++;
for(i=1;i<142;i++) {
if(twoerr[n]==crc) {
fixerr(blk,i,u|v);
fx=1;
msg.err=2;
break;
}
n++;
}
if(i<142) break;
}
if(l<k) break;
}
}
if(fx==0) {
if(verbose) fprintf(stderr,"#%d not able to fix it\n",blk->chn+1);
free(blk);
continue;
} else {
if(verbose) fprintf(stderr,"#%d fix it\n",blk->chn+1);
}
}
/* redo parity checking and remove parity */
pn=0;
for(i=0;i<blk->len;i++) {
if((numbits[blk->txt[i]]&1)==0) {
pn++;
}
blk->txt[i]&=0x7f;
}
if(pn) {
if(verbose) fprintf(stderr,"#%d parity error %d\n",blk->chn+1,pn);
free(blk);
continue;
}
/* fill msg struct */
msg.txt[0]= '\0';
msg.fid[0] = '\0';
msg.lvl = blk->lvl;
k = 0;
msg.mode = blk->txt[k];
k++;
for (i = 0; i < 7; i++, k++) {
msg.addr[i] = blk->txt[k];
}
msg.addr[7] = '\0';
/* ACK/NAK */
msg.ack = blk->txt[k];
k++;
msg.label[0] = blk->txt[k];
k++;
msg.label[1] = blk->txt[k];
if(msg.label[1]==0x7f) msg.label[1]='d';
k++;
msg.label[2] = '\0';
msg.bid = blk->txt[k];
k++;
/* STX/ETX */
msg.bs=blk->txt[k];
k++;
msg.no[0] = '\0';
msg.fid[0] = '\0';
if(msg.mode <= 0x5d) {
/* donwlink */
if(k<blk->len) {
for (i = 0; i < 4 && k<blk->len-1; i++, k++) {
msg.no[i] = blk->txt[k];
}
msg.no[i] = '\0';
msg.be=blk->txt[blk->len-1];
for (i = 0; i < 6 && k<blk->len-1; i++, k++) {
msg.fid[i] = blk->txt[k];
}
msg.fid[i] = '\0';
}
} else {
/* uplink */
if(airflt) {
free(blk);
continue;
}
}
blk->txt[blk->len-1]='\0';
strncpy(msg.txt, &(blk->txt[k]),240);msg.txt[239]=0;
if(outtype==0)
printoneline(&msg,blk->chn,blk->t);
else if (outtype==1)
printmsg(&msg,blk->chn,blk->t);
else if (outtype==2)
send_udp(&msg,blk->chn,blk->t);
free(blk);
} while(1);
}
