Need help with narray: how to return an array from a C-extension

ruby-talk
1

Hi there,
I am writing my first C extension module to ruby, and I need a little
help:
import of parameters works fine, but export of results not yet:

static VALUE
myarr_faltung1(VALUE m, VALUE distribution, VALUE lookuptable, VALUE
mu_shifted)
{
    struct NARRAY *a1, *a2;
    int mt, i;
    volatile VALUE v1, v2;

/* import from parameters seems to work */
    mt = NUM2INT(mu_shifted);
    v1 = na_cast_unless_narray(distribution,NA_DFLOAT);
    GetNArray(v1,a1);
    v2 = na_cast_unless_narray(lookuptable,NA_DFLOAT);
    GetNArray(v2,a2);

/* calculation seems to work */
    for (i=0; i<=1000; i++)
        *((double*)(a1->ptr+i)) += *((double*)(a2->ptr+mt-i));

/* PROBLEM: this does not work. QUESTION: how can I overwrite the call
parameter "distribution"
    with a ruby array that contains the result a1->ptr of the above
calculation? */
    distribution = na_to_array( a1->ref );

/* PROBLEM: the following does not work either. QUESTION: how can I
return the result a1->ptr
    of the above calculation to the calling program? */
    return a1->ref ;
}

Thanks in advance, Joachim

2

VALUE my_function(VALUE self, VALUE param) {
   VALUE result;

   result = rb_ary_new(NUM2INT(param));
   return result;
}

···

On Oct 4, 2006, at 11:30 AM, Joachim (München) wrote:

Hi there,
I am writing my first C extension module to ruby, and I need a little
help:
import of parameters works fine, but export of results not yet:

3

Hi,

From: "Joachim (München)"
I am writing my first C extension module to ruby, and I need a little
help:
import of parameters works fine, but export of results not yet:

I recommend not to manipulate the C structure of NArray
because its structure is complicated and may be changed in future.

static VALUE
myarr_faltung1(VALUE m, VALUE distribution, VALUE lookuptable, VALUE
mu_shifted)
{
    struct NARRAY *a1, *a2;
    int mt, i;
    volatile VALUE v1, v2;

/* import from parameters seems to work */
    mt = NUM2INT(mu_shifted);
    v1 = na_cast_unless_narray(distribution,NA_DFLOAT);
    GetNArray(v1,a1);
    v2 = na_cast_unless_narray(lookuptable,NA_DFLOAT);
    GetNArray(v2,a2);

  // must check array sizes here

/* calculation seems to work */
    for (i=0; i<=1000; i++)
        *((double*)(a1->ptr+i)) += *((double*)(a2->ptr+mt-i));

          *((double*)(a1->ptr)+i) += *((double*)(a2->ptr)+mt-i);
  // a1->ptr is declared as char*

/* PROBLEM: this does not work. QUESTION: how can I overwrite the call
parameter "distribution"
    with a ruby array that contains the result a1->ptr of the above
calculation? */
    distribution = na_to_array( a1->ref );

  // I think ovewriting arguments is not a good idea.
  // If you cannot avoid it, overwrite RARRAY(distribution)->ptr[i] carefully.

/* PROBLEM: the following does not work either. QUESTION: how can I
return the result a1->ptr
    of the above calculation to the calling program? */
    return a1->ref ;

      return v1;

}

Masahiro Tanaka