to_der

static VALUE
ossl_pkcs12_to_der(VALUE self)
{
    PKCS12 *p12;
    VALUE str;
    long len;
    unsigned char *p;

    GetPKCS12(self, p12);
    if((len = i2d_PKCS12(p12, NULL)) <= 0)
        ossl_raise(ePKCS12Error, NULL);
    str = rb_str_new(0, len);
    p = (unsigned char *)RSTRING_PTR(str);
    if(i2d_PKCS12(p12, &p) <= 0)
        ossl_raise(ePKCS12Error, NULL);
    ossl_str_adjust(str, p);

    return str;
}