Re: String encoding problem in R wrappers on Windows

Just for future reference, my code had an incorrect function call in it.  The correct way to create only UTF8 strings in R is as follows:

%typemap(out,noblock=1) char * 
{
  if ( $1 ) {
    PROTECT($result = Rf_mkCharCE((char *)($1), CE_UTF8));
    $result = Rf_ScalarString($result);
    UNPROTECT(1);
  } else {
    $result = R_NilValue;
  }
}

Kevin Smith
[email protected]




> On Aug 11, 2020, at 4:25 PM, William S Fulton <[email protected]> wrote:
> 
> The code in question looks like it comes from the 'out' typemap for char *, so you are probably wrapping a function returning a char *:
> 
> %typemap(out,noblock=1) char * 
>  {  $result = $1 ? Rf_mkString(%reinterpret_cast($1,char *)) : R_NilValue; }
> 
> Just add in your own version with the code you want (your code doesn't compile for me, but here it is converted into a typemap:)
> 
> %typemap(out,noblock=1) char * 
> // {  $result = $1 ? Rf_mkString(%reinterpret_cast($1,char *)) : R_NilValue; }
> {
>   if ( $1 ) {
>     PROTECT($result = Rf_mkCharCE((char *)($1), CE_UTF8));
>     $result = Rf_mkString($result);
>     UNPROTECT(1);
>   } else {
>     $result = R_NilValue;
>   }
> }
> 
> William
> 
> 
> 
> On Thu, 30 Jul 2020 at 21:42, Kevin Smith <[email protected]> wrote:
> I’m wrapping a library that uses all UTF-8 strings as results.  I noticed recently that non-ASCII characters on Windows contained incorrect characters.  I tracked it down to the use of Rf_mkString in the wrappers which I’m assuming must think the C string is encoded in the native encoding for the platform, not necessarily UTF-8.  The lines looks like:
> 
>   r_ans = result ? Rf_mkString(result) : R_NilValue;
> 
> I’m not sure how to make the wrappers work properly with UTF-8 result strings though.  The only thing I can think of is to post-process the wrappers to generate code like the following.  It forces the encoding to UTF-8.  This approach seems pretty heavy-handed though and I was wondering if there was a better solution.
> 
>   if ( result ) {
>     PROTECT(r_ans = Rf_mkCharCE((char *)(result), CE_UTF8)); 
>     r_ans = Rf_mkString(r_ans);
>     UNPROTECT(1);
>   } else {
>     r_ans = R_NilValue;
>   }
> 
> Kevin Smith
> [email protected]
> 
> 
> 
> 
> 
> 
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