Re: [Swig-user] Returning a value from C/C++ Function with output parameter - Ruby

[Roy S. <ro...@mi...>]

Piet wrote:
> Hi, all!
>
> Thanks to Roy Sutton *very much* for the answer,
> but things didn't work.
>
>   
> Did not work, because (*$1) gets accessed too early. With
> "out" or "argout" things won't compile (of course).
> I'm struggling here since two weeks(!). Does anyone still
> have a clue ?
>   
Piet,

I just tried it here and it appears to wrap perfectly.  Which version of 
SWIG are you using?  Here is my entire interface file:

%module FirstSwigTest

%typemap(argout) char**
{
    VALUE arr = rb_ary_new2(1024);
    int Len = strlen(*$1);
    for (int i=0; i<Len; i++)
    {
        rb_ary_push(arr, (*$1)[i]);
    }
    $result = arr;
}

%typemap(in, numinputs=0) (char ** OUTPUT) (char * tmp) {
 // Don't know if you need to allocate space or anything, but if so, do 
it here
 // If you do, you'll need a typemap to free the space
  $1 = &tmp
}

extern "C" bool Go(char** OUTPUT);

The resulting output:

SWIGINTERN VALUE
_wrap_Go(int argc, VALUE *argv, VALUE self) {
  char **arg1 = (char **) 0 ;
  bool result;
  char *tmp1 ;
  VALUE vresult = Qnil;
 
  {
    // Don't know if you need to allocate space or anything, but if so, 
do it here
    // If you do, you'll need a typemap to free the space
    arg1 = &tmp1
  }
  if ((argc < 0) || (argc > 0)) {
    rb_raise(rb_eArgError, "wrong # of arguments(%d for 0)",argc); 
SWIG_fail;
  }
  result = (bool)Go(arg1);
  vresult = SWIG_From_bool(static_cast< bool >(result));
... >snip<

Roy