to_der

static VALUE
ossl_ocspreq_to_der(VALUE self)
{
    OCSP_REQUEST *req;
    VALUE str;
    unsigned char *p;
    long len;

    GetOCSPReq(self, req);
    if((len = i2d_OCSP_REQUEST(req, NULL)) <= 0)
        ossl_raise(eOCSPError, NULL);
    str = rb_str_new(0, len);
    p = (unsigned char *)RSTRING_PTR(str);
    if(i2d_OCSP_REQUEST(req, &p) <= 0)
        ossl_raise(eOCSPError, NULL);
    ossl_str_adjust(str, p);

    return str;
}