OpenSSL::PKey::EC#dsa_sign_asn1

static VALUE ossl_ec_key_dsa_sign_asn1(VALUE self, VALUE data)
{
    EC_KEY *ec;
    unsigned int buf_len;
    VALUE str;

    GetEC(self, ec);
    StringValue(data);

    if (EC_KEY_get0_private_key(ec) == NULL)
        ossl_raise(eECError, "Private EC key needed!");

    str = rb_str_new(0, ECDSA_size(ec));
    if (ECDSA_sign(0, (unsigned char *) RSTRING_PTR(data), RSTRING_LENINT(data), (unsigned char *) RSTRING_PTR(str), &buf_len, ec) != 1)
        ossl_raise(eECError, "ECDSA_sign");
    rb_str_set_len(str, buf_len);

    return str;
}