new

static VALUE
initialize(int argc, VALUE argv[], VALUE self)
{
    ffi_cif * cif;
    ffi_type **arg_types;
    ffi_status result;
    VALUE ptr, args, ret_type, abi;
    int i;

    rb_scan_args(argc, argv, "31", &ptr, &args, &ret_type, &abi);
    if(NIL_P(abi)) abi = INT2NUM(FFI_DEFAULT_ABI);

    Check_Type(args, T_ARRAY);

    rb_iv_set(self, "@ptr", ptr);
    rb_iv_set(self, "@args", args);
    rb_iv_set(self, "@return_type", ret_type);
    rb_iv_set(self, "@abi", abi);

    TypedData_Get_Struct(self, ffi_cif, &function_data_type, cif);

    arg_types = xcalloc(RARRAY_LEN(args) + 1, sizeof(ffi_type *));

    for (i = 0; i < RARRAY_LEN(args); i++) {
        int type = NUM2INT(RARRAY_PTR(args)[i]);
        arg_types[i] = INT2FFI_TYPE(type);
    }
    arg_types[RARRAY_LEN(args)] = NULL;

    result = ffi_prep_cif (
            cif,
            NUM2INT(abi),
            RARRAY_LENINT(args),
            INT2FFI_TYPE(NUM2INT(ret_type)),
            arg_types);

    if (result)
        rb_raise(rb_eRuntimeError, "error creating CIF %d", result);

    return self;
}