Re: [liblo] how to connect to a liblo TCP OSC server?

[Fernando C. <fca...@gm...>]

Hello Mark, thanks for replying.

So I can simply access the fields of the "argv" union, based upon the
value of "type". Excellent.

I looked at lo_osc_types.h as a reference.
It seems to me, that some types may have more than one corresponding
field. How to choose?

Example 1:
I have type = LO_STRING, which is 's'
Should I read &argv[n]->S or &argv[n]->s ?

Example 2:
I have type = LO_INT32, which is 'i'
Should I read argv[n]->i or argv[n]->i32 ?

Same goes for 'f' (read from ->f or ->f32 ?)

Thanks for the clarification

Fernando



Il giorno dom 28 feb 2021 alle ore 23:34 Mark Hotchkiss
<Ma...@re...> ha scritto:
>
> Hi Fernando,
>
> I assume that you are talking about fetching the passed values out from a received message in the message handler. The values are each passed in a union.
>
> Here is one of my message handlers (sorry if it doesn't format well in an email):
>
>
> //      Callback handler for "/request/write <id> <node> <location> <parameter size> <parameter ID> <parameter format> <value>"
>
> //                              or                       <id> <node> <location> <parameter name> <parameter format> <value>"
>
> int             handler_reqwrite(const char *path, const char *types, lo_arg **argv, int argc, lo_message msg, void *user_data)
>
> {
>         if ( *(types+3) == 'i')                                                 // if the forth parameter is a size and not a name . . .
>
>                 if ( argv[2]->i == -1 )                                         // and if the location is ram and not a flash page . . .
>
>                         requestWrite( (void*)argv[0]->i, argv[1]->i, argv[3]->i, argv[4]->i, argv[5]->i, argv[6]);
>                 else
>                         requestWriteFlash( (void*)argv[0]->i, argv[1]->i, argv[3]->i, argv[4]->i, argv[5]->i, argv[6]);
>         else                                                                                                    // if the forth parameter is a name and not a size . . .
>
>                 if ( argv[2]->i == -1 )                                         // and if the location is ram and not a flash page . . .
>
>                         requestWriteByName( (void*)argv[0]->i, argv[1]->i, &argv[3]->s, argv[4]->i, argv[5]);
>                 else
>                         requestWriteFlashByName( (void*)argv[0]->i, argv[1]->i, &argv[3]->s, argv[4]->i, argv[5]);
>         return 0;
> }
>
>
> Each 'lo_arg' type is a union of all of the OSC types and each 'argv' is a pointer to a union. As an example, if the second value passed was an 'int', then I would access it as:
>
>         int size = argv[1]->i ;
>
> and if it was a string (which is actually a character-pointer, so we have a pointer to a pointer):
>
>         char* name = &argv[1]->s ;
>
> Of course, the 'types' parameter would tell you the true type of the parameter so that you can access it correctly, and I have caused segmentation faults when I made the wrong assumption of the type.
>
> Is that what you needed? Let me know if you would like anything else. I have a ton of code now.
>
> Mark
>
>
>
> -----Original Message-----
> From: Fernando Carello [mailto:fca...@gm...]
> Sent: Sunday, February 28, 2021 9:00 AM
> To: liblo development list
> Subject: Re: [liblo] how to connect to a liblo TCP OSC server?
>
>
> Hello,
> I've successfully tested liblo in C, writing both client and server
> implementations.
>
> Now I'm faced with a maybe silly problem...
>
> I can compose an OSC message from native C types using
> lo_message_new() and appropriate
> lo_message_add_* methods.
>
> But, how may I convert OSC arguments from lo_arg to native C types?
>
> Thanks!
> Fernando
>
>
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