Re: Native Calls with SEXP (a variant type, with subtypes for all R’s data structures).

[Alexander Burger]

On Wed, Apr 07, 2021 at 07:46:20AM +0200, Alexander Burger wrote:
> OK, so now we have a pointer to a structure filled by evalInR().
> ...
>    (struct (evalInR "6*4") ...)

In fact this depends on what exactly evalInR() returns.

If it returns a pointer to a dynamically allocated structure, and the caller is
responsible to de-allocate it, you would do

   (let P (evalInR "6*4")
      (prog1
         (struct P ...)
         (free P) ) )

If, however, the structure is statically allocated, you can also give the
structure's structure directly as the return value specification:

   (native `*RinC "evalInR" '(...) "Cmd")

For example, as a (somewhat conceived) test case

   static struct {
      char *s;
      int i[4];
      double d;
      char nm[8];
   } Data;

   void *foo(void) {
      Data.s = "Hello";
      Data.i[0] = 1;
      Data.i[1] = 2;
      Data.i[2] = -3;
      Data.i[3] = 4;
      Data.d = 0.99;
      strcpy(Data.nm, "world");
      return &Data;
   }

Then in the REPL

   : (native "./test.so" "foo" '(S I (I . 2) (B . 4) 100 (C . 8)))
   -> ("Hello" 1 (2 -3) (4 0 0 0) 99 ("w" "o" "r" "l" "d"))

☺/ A!ex

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