/*

* Copyright (c) 2014 Thierry Leconte (f4dwv)

*

*

* This code is free software; you can redistribute it and/or modify

* it under the terms of the GNU Library General Public License version 2

* published by the Free Software Foundation.

*

* This program is distributed in the hope that it will be useful,

* but WITHOUT ANY WARRANTY; without even the implied warranty of

* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

* GNU Library General Public License for more details.

*

* You should have received a copy of the GNU Library General Public

* License along with this library; if not, write to the Free Software

* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*

*/

#include <stdlib.h>

#include <stdio.h>

#include <time.h>

#include <string.h>

#include <pthread.h>

#include <math.h>

#include "acarsdec.h"

#include "acars.h"

#define SYN 0x16

#define SOH 0x01

#define STX 0x02

#define ETX 0x83

#define ETB 0x97

#define DLE 0x7f

static const unsigned char numbits[256]={

0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4,1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,

1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,

1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,

2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,

1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,

2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,

2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,

3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,4,5,5,6,5,6,6,7,5,6,6,7,6,7,7,8

};

#include "syndrom.h"

const unsigned short crc_ccitt_table[256] = {

0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,

0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,

0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,

0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,

0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,

0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,

0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,

0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,

0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,

0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,

0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,

0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,

0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,

0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,

0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,

0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,

0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,

0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,

0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,

0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,

0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,

0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,

0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,

0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,

0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,

0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,

0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,

0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,

0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,

0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,

0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,

0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78

};

static pthread_mutex_t blkmtx=PTHREAD_MUTEX_INITIALIZER;

static pthread_cond_t blkwcd= PTHREAD_COND_INITIALIZER;

static msgblk_t *blkq_s=NULL;

static msgblk_t *blkq_e=NULL;

#define update_crc(crc,c) crc= (crc>> 8)^crc_ccitt_table[(crc^(c))&0xff];

static void printtime(time_t t)

{

struct tm *tmp;

if(t==0) return;

tmp = gmtime(&t);

printf ("%02d/%02d/%04d %02d:%02d:%02d",

tmp->tm_mday, tmp->tm_mon + 1, tmp->tm_year + 1900,

tmp->tm_hour, tmp->tm_min, tmp->tm_sec);

}

static void cleantxt(char *txt)

{

char *ptr;

for(ptr=txt;*ptr;ptr++)

if((*ptr<' ' || *ptr>126) && *ptr !='\n') *ptr=' ';

}

static void printmsg(acarsmsg_t *msg,int chn,time_t t)

{

printf("\n[#%1d (%3d/%1d) ",chn+1,msg->lvl,msg->err);

printtime(t);

printf(" ----------------------------------------------------------\n");

printf("Aircraft reg: %s ", msg->addr);

if(msg->bs!=0x03) printf("Flight id: %s", msg->fid);

printf("\n");

printf("Mode: %c ", msg->mode);

printf("Msg. label: %s\n", msg->label);

printf("Block id: %x ", (int) msg->bid);

printf("Ack: %x\n", msg->ack);

printf("Msg. no: %s\n", msg->no);

if(msg->bs==0x03)

printf("No Text\n");

else {

cleantxt(msg->txt);

printf("Message :\n%s\n", msg->txt);

}

if(msg->be==0x17) printf("Block End\n");

fflush(stdout);

}

static void printoneline(acarsmsg_t *msg,int chn,time_t t)

{

char txt[34];

char *pstr;

strncpy(txt,msg->txt,34);txt[33]=0;

cleantxt(txt);

strtok_r(txt,"\n",&pstr);

printf("#%1d %7s %6s %2s %4s ", chn+1,msg->addr,msg->fid,msg->label,msg->no);

printtime(t);

printf(" %s\n", txt);

fflush(stdout);

}

static void fixerr(msgblk_t *blk,int sft,unsigned char msk)

{

if(sft<=2) {

if(verbose) fprintf(stderr,"#%d error in CRC\n",blk->chn+1);

return;

}

blk->txt[blk->len-1-(sft-2)]^=msk;

}

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);

}

int initAcars(channel_t *ch)

{

pthread_t th;

ch->outbits=0;

ch->nbits=8;

ch->Acarsstate=WSYN;

ch->blk=malloc(sizeof(msgblk_t));

ch->blk->chn=ch->chn;

pthread_create(&th,NULL,blk_thread,NULL);

return 0;

}

void decodeAcars(channel_t *ch)

{

unsigned char r=ch->outbits;

switch (ch->Acarsstate) {

case WSYN:

if (r==SYN) {

ch->Acarsstate = SYN2;

ch->nbits=8;

return;

}

if (r==(unsigned char)~SYN) {

ch->MskS^=2;

ch->Acarsstate = SYN2;

ch->nbits=8;

return;

}

ch->nbits=1;

return;

case SYN2:

if (r==SYN) {

ch->Acarsstate = SOH1;

ch->nbits=8;

return ;

}

if (r==(unsigned char)~SYN) {

ch->MskS^=2;

ch->nbits=8;

return;

}

ch->Acarsstate = WSYN;

ch->nbits=1;

return;

case SOH1:

if (r==SOH) {

if(inpmode!=2) ch->blk->t = time(NULL);

else ch->blk->t=0;

ch->Acarsstate = TXT;

ch->blk->len=0;

ch->nbits=8;

return ;

}

ch->Acarsstate = WSYN;

ch->nbits=1;

return;

case TXT:

ch->blk->txt[ch->blk->len] = r;

ch->blk->len++;

if (r == ETX || r == ETB) {

ch->Acarsstate = CRC1;

ch->nbits=8;

return ;

}

if (ch->blk->len>20 && r==DLE) {

if(verbose) fprintf(stderr,"#%d miss txt end\n",ch->chn+1);

ch->blk->len-=3;

ch->blk->crc[0]=ch->blk->txt[ch->blk->len];

ch->blk->crc[1]=ch->blk->txt[ch->blk->len+1];

ch->Acarsstate = CRC2;

goto putmsg_lbl;

}

if (ch->blk->len > 240) {

if(verbose) fprintf(stderr,"#%d too long\n",ch->chn+1);

ch->Acarsstate = WSYN;

ch->nbits=1;

return;

}

ch->nbits=8;

return ;

case CRC1:

ch->blk->crc[0]=r;

ch->Acarsstate = CRC2;

ch->nbits=8;

return ;

case CRC2:

ch->blk->crc[1]=r;

ch->blk->lvl=20*log10(ch->Mskdc)-81.0;

putmsg_lbl:

pthread_mutex_lock(&blkmtx);

ch->blk->prev=NULL;

if(blkq_s) blkq_s->prev=ch->blk;

blkq_s=ch->blk;

if(blkq_e==NULL) blkq_e=blkq_s;

pthread_cond_signal(&blkwcd);

pthread_mutex_unlock(&blkmtx);

ch->blk=malloc(sizeof(msgblk_t));

ch->blk->chn=ch->chn;

ch->Acarsstate = END;

ch->nbits=8;

return ;

case END:

ch->Acarsstate = WSYN;

ch->nbits=8;

return ;

}

}