Calling ICU APIs from RPG

[Luca Altmann]

I'm trying to call an ICU APIs from RPG but can't get it running and i think its due to parameter mismatch.
https://unicode-org.github.io/icu-do.../uidna_8h.html - API "uidna_IDNToASCII()"


My code looks like following:

**free
Ctl-Opt BndDir('QICU/QXICUAPIBD');

//************************************************** **
// Prototypes *
//************************************************** **
Dcl-Pr StrToPunycode Int(10) ExtProc('uidna_IDNToASCII_4_0');
  Src Uns(5) Value;
  SrcLen Int(10);
  Dest Uns(5) Value;
  DestCapacity Int(10);
  Options Int(10);
  ParseError LikeDs(ParseError);
  ErrorCode Int(10);
End-Pr;

//************************************************** **
// Variables *
//************************************************** **
Dcl-Ds Src Qualified;
  Dec Uns(5) Inz(0);
  Value UCS2(64) Pos(1);
End-Ds;

Dcl-Ds Dest Qualified;
  Value UCS2(64) Inz('');
  Dec Uns(5);
End-Ds;

Dcl-S DestCapacity Int(10);
Dcl-S Options Int(10);
Dcl-S ErrorCode Int(10);
Dcl-S Len Int(10);
Dcl-S SrcLen Int(10);

Dcl-Ds ParseError Qualified;
  Line Int(10);
  Offset Int(10);
  Dcl-Ds PreContext;
    Value UCS2(32) Inz('');
    Dec Uns(5) Pos(1);
  End-Ds;
  Dcl-Ds PostContext;
    Value UCS2(32) Inz('');
    Dec Uns(5) Pos(1);
  End-Ds;
End-Ds;

//************************************************** **
// Main *
//************************************************** **
Src.Value = 'HALLÖ.COM';
SrcLen = %Len(Src.Value);
DestCapacity = %Size(Dest.Value);
Options = *Zero;

Len = StrToPunycode(Src.Dec :
                     SrcLen :
                   Dest.Dec :
               DestCapacity :
                    Options :
                 ParseError :
                 ErrorCode) ;

*INLR = *On;

I think i got the Int(10) Parameters right but the UCHAR (Src, Dest, ParseError) Parameters seem wrong. Does anyone know how to define the UCHAR Parameters in RPG.

Thanks in advance
Luca Altmann