Re: [gpsd-users] Passing metadata through gpsd

[Ed Simmons]

Hi Roy,

On 15/04/14 04:39, Roy Barkas wrote:
> Some time ago Eric said that it is possible to pass metadata through 
> gpsd and have the metadata appear as (I hope) an element of the gpsd 
> json output.
>
> I now need to implement this in order to pass some ais message 
> metadata through to the end user.
>
> The AIS messages that I receive are wrapped in a non-standard format 
> that includes some info that I need to preserve and pass along.
>
> If I was correct that this is possible, how can I do it?  It isn't 
> obvious to me how I should go about packaging the desired metadata and 
> sending it to gpsd so that it comes out the other end.
>
> Cheers;
>
> RoyHB
>
> p.s.:  The split24 functionality that was released with 3.9 works 
> beautifully - thanks for adding it.
It's some time since I played with the innards of GPSD...

What I did was to add to the parser so that the data of interest is 
understood by GPSD itself, then modify the json code to be aware of 
these new variables that are collected by the parser.

packet.c contains the state machine for understanding the packets.

I added the variables I needed to struct attitude_t in gps.h as this was 
the appropriate place for my attitude related data to be stored.

You would need to ensure the packet sniffer correctly identifies your 
messages and hands them on to driver_ais.c - here you'd need to add the 
code to parse the data you want and store it.

In gpsd_json.c you would then need to add appropriate code to output 
your newly added variables contents...

I hope that helps... I'm a little rusty on this, thanks to our SVN I can 
tell you what I did!

Best,
Ed