error parsing ais message type 5

[handerpeder]

I'm having an issue parsing incoming messages with ais message type 5. Parsing these message works with AisLib.

Please advise.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "portable.h"
#include "nmea.h"
#include "sixbit.h"
#include "vdm_parse.h"


int main( int argc, char *argv[] )
{
  int i = 0;
    ais_state ais;
    aismsg_5 msg_5;

    memset( &ais, 0, sizeof( ais_state ) );
    char *msg[] =
      {
       "!BSVDM,2,2,4,A,54SkDki@000,2*06",
       "!BSVDM,2,2,1,A,50E@0000000,2*3C",
       "!BSVDM,2,2,7,A,5`5QAhH8880,2*52",
       "!BSVDM,2,2,3,A,5H888888880,2*43",
       "!BSVDM,2,2,3,B,54SkDki@000,2*02",
       "!BSVDM,2,2,9,B,50E@0000000,2*37",
       "!BSVDM,2,2,2,A,5P@Ah000000,2*03",
       "!BSVDM,2,2,6,A,5`5QAhH8880,2*53",
       "!BSVDM,2,2,8,B,5H888888880,2*4B",
       "!BSVDM,2,2,2,B,5R1`0j8<M`0,2*79",
       "!BSVDM,1,1,,A,53mFl:400000hoG3;@0pE1ADp000,0*39"
    };

    for(i = 0; i < (sizeof(msg) / sizeof(const char*)) ; i++) {
      if(assemble_vdm( &ais, msg[i]) == 0) {
        ais.msgid = (unsigned char) get_6bit( &ais.six_state, 6 );
        printf("msgid: %d, parse result: %d\n", ais.msgid, parse_ais_5(&ais, &msg_5));
      }
    }

    return 0;
}

Output:

msgid: 5, parse result: 2
msgid: 5, parse result: 2
msgid: 5, parse result: 2
msgid: 5, parse result: 2
msgid: 5, parse result: 2
msgid: 5, parse result: 2
msgid: 5, parse result: 2
msgid: 5, parse result: 2
msgid: 5, parse result: 2
msgid: 5, parse result: 2
msgid: 5, parse result: 2

[bcl]

Error 2 means you don't have enough bits for the message. Looking at your example data I see a couple of things that are going to cause problems:

• The messages are out of order (see the sequence #) and are incomplete.
• The 1,1 message should be complete, but it is too short for a message 5
• You need to reset the ais struct on errors or when it is finished assembling a message
• Check the return code of assemble_vdm

I do note that assemble_vdm doesn't give an error 5 when you feed it the out of sequence sentences so I'll look into that.

[bcl]

Fixed by #19