Re: Passing integer pointer in XS?

Provides the specified interface:

#define _MAX_PROTOCOL_LEN 25
#define _MAX_MODEL_LEN    25

int
tdSensor(SV* protocol_sv, SV* model_sv, SV* id_sv, SV* dataTypes_sv)
   CODE:
   {
      char protocol[_MAX_PROTOCOL_LEN + 1];
      char model[_MAX_MODEL_LEN + 1];
      int  id;
      int  dataTypes;

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

      if (RETVAL == TELLSTICK_SUCCESS) {
         SV* sv;
         sv = sv_2mortal(newSVpv(protocol, 0)));  SvSetMagicSV(protoco
+l_sv,  sv);
         sv = sv_2mortal(newSVpv(model, 0));      SvSetMagicSV(model_s
+v,     sv);
         sv = sv_2mortal(newIV(id));              SvSetMagicSV(id_sv, 
+       sv);
         sv = sv_2mortal(newIV(dataTypes));       SvSetMagicSV(dataTyp
+es_sv, sv);
      } else {
         SvSetMagicSV(protocol_sv,  &PL_sv_undef);
         SvSetMagicSV(model_sv,     &PL_sv_undef);
         SvSetMagicSV(id_sv,        &PL_sv_undef);
         SvSetMagicSV(dataTypes_sv, &PL_sv_undef);
      }
   }
   OUTPUT:
       RETVAL
[download]

Untested.

Provides a more Perlish interface:

#define _MAX_PROTOCOL_LEN 25
#define _MAX_MODEL_LEN    25

SV*
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) {
         HV* hv = newHV();
         SV* sv;
 
         /* In theory, hv_stores can fail.                        */
         /* However, I suspect it can't happen for this new hash. */
         /* It it were to happen here, this code would leak.      */
         sv = newSVpv(protocol, 0);  hv_stores(hv, "protocol",  sv);
         sv = newSVpv(model, 0);     hv_stores(hv, "model",     sv);
         sv = newIV(id);             hv_stores(hv, "id",        sv);
         sv = newIV(dataTypes);      hv_stores(hv, "dataTypes", sv);

         RETVAL = newRV_noinc(MUTABLE_SV(hv));
      } else {
         RETVAL = &PL_sv_undef;
      }
   }
   OUTPUT:
       RETVAL
[download]

Usage:

use feature qw( say );

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

Untested.

Update: Fixed missing sv declaration and missing typecast for newRV_noinc's argument.

Comment on Re: Passing integer pointer in XS? Select or Download Code

Replies are listed 'Best First'.
Re^2: Passing integer pointer in XS? by martin67 (Novice) on Jul 18, 2016 at 20:56 UTC
Thank you! This looks interesting - and definately a new area of Perl for me... I tried to compile it but ran into an error: `TellStick.xs:70:10: error: ‘sv’ undeclared (first use in this function +)` [download] I guess sv needs to be declared. And there was a typo for NewSViv. So now it looks like `if (rv == TELLSTICK_SUCCESS) { HV* hv = newHV(); SV sv = newSV(0); sv = newSVpv(protocol, 0); hv_stores(hv, "protocol", sv); sv = newSVpv(model, 0); hv_stores(hv, "model", sv); sv = newSViv(id); hv_stores(hv, "id", sv); sv = newSViv(dataTypes); hv_stores(hv, "dataTypes", sv); RETVAL = newRV_noinc(hv); } else { RETVAL = &PL_sv_undef; }` [download] There were some compilation warnings as well, don't know if they are important: In file included from /usr/lib/arm-linux-gnueabihf/perl/5.20/CORE/perl +.h:5102:0, from TellStick.xs:2: TellStick.xs: In function ‘XS_TellStick_tdSensor’: TellStick.xs:76:31: warning: passing argument 2 of ‘Perl_newRV_noinc’ +from incompatible pointer type RETVAL = newRV_noinc(hv); ^ /usr/lib/arm-linux-gnueabihf/perl/5.20/CORE/embed.h:371:48: note: in d +efinition of macro ‘newRV_noinc’ #define newRV_noinc(a) Perl_newRV_noinc(aTHX_ a) ^ In file included from /usr/lib/arm-linux-gnueabihf/perl/5.20/CORE/perl +.h:5061:0, from TellStick.xs:2: /usr/lib/arm-linux-gnueabihf/perl/5.20/CORE/proto.h:2874:19: note: exp +ected ‘struct SV const’ but argument is of type ‘struct HV ’ PERL_CALLCONV SV Perl_newRV_noinc(pTHX_ SV *const sv) [download] But the code works!!! I get the correct values: `protocol: mandolyn, model: temperaturehumidity, sensorId: 51, dataType +s: 3 protocol: mandolyn, model: temperaturehumidity, sensorId: 61, dataType +s: 3` [download] Thank you very much for your help! Now I have a way forward for implementing the rest of fucntion in the C library.	[reply] [d/l] [select]
Re^3: Passing integer pointer in XS? (XS << Perl) by tye (Sage) on Jul 18, 2016 at 21:10 UTC
This is the kind of code that, in my experience, is one of the most likely sources of particularly troublesome errors/bugs. If you want to provide a Perlish interface, then I'd implement that in Perl code, not in XS code. If you are having to deal with reference counts, for example, then you are highly likely to get it wrong sooner rather than later and more than once and probably not always notice the problem before you release the code. Just write a tiny wrapper function in mundane Perl code and have that call the very, very thinly wrapped XS that calls the C code. Only do in XS those things that you really have to do in XS. - tye	[reply]
Re^4: Passing integer pointer in XS? (XS << Perl) by ikegami (Patriarch) on Jul 18, 2016 at 21:31 UTC
What would be simpler than returning them in a hash? ...oh yeah, returning them in a list! Here ya go. `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.	[reply] [d/l] [select]
Re^5: Passing integer pointer in XS? (simpler) by tye (Sage) on Jul 18, 2016 at 22:14 UTC
Re^6: Passing integer pointer in XS? (simpler) by ikegami (Patriarch) on Jul 19, 2016 at 07:02 UTC
Some notes below your chosen depth have not been shown here
Re^3: Passing integer pointer in XS? by ikegami (Patriarch) on Jul 18, 2016 at 21:18 UTC
`SV sv = newSV(0);` leaks. You want `SV sv;` The other issue is because I forgot to cast it. `newRV_noinc(hv)` should be `newRV_noinc(MUTABLE_SV(hv))`. Fixed in original.	[reply] [d/l] [select]


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