C FFI

Demonstrate the C-FFI of your language. Show how to wrap an hypothetic C library that contains these three functions in its header file:

void myfunc_a();
float myfunc_b(int, float);
char *myfunc_c(int *);

The header file is named "mylib.h", and link against the lib with -lmylib and compile with -I/usr/include/mylib. Provide all the files included a Makefile.

OCaml

file "mylib.ml": <lang ocaml>external myfunc_a: unit -> unit = "caml_myfunc_a" external myfunc_b: int -> float -> float = "caml_myfunc_b" external myfunc_c: int array -> string = "caml_myfunc_c"</lang>

file "wrap_mylib.c": <lang C>#include <caml/mlvalues.h>

1. include <caml/alloc.h>
2. include <mylib.h>

CAMLprim value caml_myfunc_a(value unit) {

   myfunc_a();
   return Val_unit;

}

CAMLprim value caml_myfunc_b(value a; value b) {

   float c = myfunc_b(Int_val(a), Double_val(b));
   return caml_copy_double(c);

}

CAMLprim value caml_myfunc_c(value ml_array) {

   int i, len;
   int *arr;
   char *s;
   len = Wosize_val(ml_array);
   arr = malloc(len * sizeof(int));
   for (i=0; i < len; i++) {
       arr[i] = Int_val(Field(ml_array, i));
   }
   char *s = myfunc_c(int *);
   free(arr);
   return caml_copy_string(s);

}</lang>

the Makefile: <lang Makefile>wrap_mylib.o: wrap_mylib.c

       ocamlc -c -ccopt -I/usr/include/mylib $<

dllmylib_stubs.so: wrap_mylib.o

       ocamlmklib -o mylib_stubs $< -lmylib

mylib.mli: mylib.ml

       ocamlc -i $< > $@

mylib.cmi: mylib.mli

       ocamlc -c $<

mylib.cmo: mylib.ml mylib.cmi

       ocamlc -c $<

mylib.cma: mylib.cmo dllmylib_stubs.so

       ocamlc -a -o $@ $< -dllib -lmylib_stubs -cclib -lmylib

mylib.cmx: mylib.ml mylib.cmi

       ocamlopt -c $<

mylib.cmxa: mylib.cmx dllmylib_stubs.so

       ocamlopt -a -o $@ $< -cclib -lmylib_stubs -cclib -lmylib

clean:

       rm -f *.[oa] *.so *.cm[ixoa] *.cmxa</lang>

the file mylib.cma is used for the interpreted and bytecode modes, and mylib.cmxa is for the native mode.