[R] Returnin char back through the .Call interface

[Roger Bivand]

On Wed, 4 Feb 2004, wolski wrote:

> Hi!
> 
> My results or error messages are copied in a string and than have to be
> passed back through the .Call interface togheter with numeric results
> What is the best way to allocate storage to a character? (R_alloc?) And
> how to add it to a list? (e.g. allocVector(VECSXP, 9))
> 
> 
> Help are highly appreciated.

Again, browsing the header files usually helps. A short and probably not 
ideal example (COPY_TO_USER_STRING() does the work):

SEXP R_G_get_gisrc_file() {
      SEXP ans;
      char *gisrc;
      
      PROTECT(ans=NEW_CHARACTER(1));
      gisrc = G__get_gisrc_file();
      if (gisrc) {
	   gisrc = G_store(gisrc);
           SET_STRING_ELT(ans, 0,
                COPY_TO_USER_STRING(gisrc));
      } else {
           SET_STRING_ELT(ans, 0,
                COPY_TO_USER_STRING("empty"));
       }
      UNPROTECT(1);
      return(ans);
}


> 
> Eryk
> 
> 
> 
> Ps.
> I tried a with mkChar
> and with
> PROTECT(ral1 = NEW_CHARACTER(1));
> 
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-- 
Roger Bivand
Econonic Geography Section, Department of Economics, Norwegian School of 
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen, 
Norway, voice: +47-55959355, fax: +47-55959393; Roger.Bivand at nhh.no