void
tdSensor()
   CODE:
   {
      char protocol[_MAX_PROTOCOL_LEN + 1];
      char model[_MAX_MODEL_LEN + 1];
      int  id;
      int  dataTypes;

      int rv = tdSensor(
         protocol, sizeof(protocol),
         model, sizeof(model),
         &id,
         &dataTypes
      );

      if (rv != TELLSTICK_SUCCESS) {
         XSRETURN(0);
      }

      EXTEND(SP, 4);
      ST(0) = sv_2mortal(newSVpv(protocol, 0)));
      ST(1) = sv_2mortal(newSVpv(model, 0));
      ST(2) = sv_2mortal(newIV(id));
      ST(3) = sv_2mortal(newIV(dataTypes));
      XSRETURN(4);
   }
[download]

Usage:

use feature qw( say );

while (my ($protocol, $model, $id, $dataTypes) = tdSensor()) {
   say join ', ',
      "protocol: $protocol",
      "model: $model",
      "sensorId: $id",
      "dataTypes: $dataTypes";
}
[download]

Untested.

If the first 4 arguments are for specifying ways to output 2 strings, then you can get simpler than that!

int
tdSensor( protocol, protocolLen, model, modelLen, id, dataTypes )
        SV *    protocol
        int     protocolLen
        SV *    model
        int     modelLen
        int &   id
        int &   dataTypes
CODE:
    {
        STRLEN n_a;
        (void) SvPV_force( protocol, n_a );
        (void) SvPV_force( model, n_a );
        SvGROW( protocol, protocolLen );
        SvGROW( model, modelLen );
    }
    RETVAL = tdSensor(
        SvPV(protocol), protocolLen, SvPV(model), modelLen, &id, &data
+Types );
    SvCUR_set( protocol, strlen(SvPV(protocol)) );
    SvCUR_set( model, strlen(SvPV(model)) );
OUTPUT:
    RETVAL
    id
    dataTypes
[download]

But much simpler (and less likely to be buggy) than even that is:

int
_tdSensor( protocol, protocolLen, model, modelLen, id, dataTypes )
        char *  protocol
        int     protocolLen
        char *  model
        int     modelLen
        int &   id
        int &   dataTypes
CODE:
    RETVAL = tdSensor( protocol, protocolLen, model, modelLen, &id, &d
+ataTypes );
OUTPUT:
    RETVAL
    id
    dataTypes
[download]

Plus

sub tdSensor {
    my( $protocolLen, $modelLen ) = @_;
    $protcolLen ||= 1024;
    $modelLen ||= 1024;
    my $protocol = '\0' x $protcolLen;
    my $model = '\0' x $modelLen;
    my $id = 0;
    my $dataTypes = 0;
    my $ret = _tdSensor(
        $protocol, $protocolLen, $model, $modelLen, $id, $dataTypes );
    s/\0.*//
        for $protocol, $model;
    return( $ret, $protocol, $model, $id, $dataTypes );
}
[download]

Which has the significant advantage of making it much easier to improve the interface without having to futz with the super finicky XS part of the code.

- tye        

But much simpler (and less likely to be buggy) than even that is:

Didn't I already demonstrate that it's quite buggy? (Ok, so you're relying on the fact that manipulating the internal buffer of the scalar works in this situation even though you're not allowed to do it. As far as I'm concerned, you can't call simple something that relies on this level of knowledge of internals.)

If the first 4 arguments are for specifying ways to output 2 strings, then you can get simpler than that!

Really? Cause I would need to perform some testing to verify that it's correct. All that magic is far far more complicated than just returning the values.