class OpenSSL::PKey::EC::Group

static VALUE ossl_ec_group_initialize(int argc, VALUE *argv, VALUE self)
{
    VALUE arg1, arg2, arg3, arg4;
    EC_GROUP *group;

    TypedData_Get_Struct(self, EC_GROUP, &ossl_ec_group_type, group);
    if (group)
        ossl_raise(rb_eRuntimeError, "EC_GROUP is already initialized");

    switch (rb_scan_args(argc, argv, "13", &arg1, &arg2, &arg3, &arg4)) {
    case 1:
        if (rb_obj_is_kind_of(arg1, cEC_GROUP)) {
            const EC_GROUP *arg1_group;

            GetECGroup(arg1, arg1_group);
            if ((group = EC_GROUP_dup(arg1_group)) == NULL)
                ossl_raise(eEC_GROUP, "EC_GROUP_dup");
        } else {
            BIO *in = ossl_obj2bio(&arg1);

            group = PEM_read_bio_ECPKParameters(in, NULL, NULL, NULL);
            if (!group) {
                OSSL_BIO_reset(in);
                group = d2i_ECPKParameters_bio(in, NULL);
            }

            BIO_free(in);

            if (!group) {
                const char *name = StringValueCStr(arg1);
                int nid = OBJ_sn2nid(name);

                ossl_clear_error(); /* ignore errors in d2i_ECPKParameters_bio() */
                if (nid == NID_undef)
                    ossl_raise(eEC_GROUP, "unknown curve name (%"PRIsVALUE")", arg1);

                group = EC_GROUP_new_by_curve_name(nid);
                if (group == NULL)
                    ossl_raise(eEC_GROUP, "unable to create curve (%"PRIsVALUE")", arg1);

                EC_GROUP_set_asn1_flag(group, OPENSSL_EC_NAMED_CURVE);
                EC_GROUP_set_point_conversion_form(group, POINT_CONVERSION_UNCOMPRESSED);
            }
        }

        break;
    case 4:
        if (SYMBOL_P(arg1)) {
            ID id = SYM2ID(arg1);
            EC_GROUP *(*new_curve)(const BIGNUM *, const BIGNUM *, const BIGNUM *, BN_CTX *) = NULL;
            const BIGNUM *p = GetBNPtr(arg2);
            const BIGNUM *a = GetBNPtr(arg3);
            const BIGNUM *b = GetBNPtr(arg4);

            if (id == s_GFp) {
                new_curve = EC_GROUP_new_curve_GFp;
#if !defined(OPENSSL_NO_EC2M)
            } else if (id == s_GF2m) {
                new_curve = EC_GROUP_new_curve_GF2m;
#endif
            } else {
                ossl_raise(rb_eArgError, "unknown symbol, must be :GFp or :GF2m");
            }

            if ((group = new_curve(p, a, b, ossl_bn_ctx)) == NULL)
                ossl_raise(eEC_GROUP, "EC_GROUP_new_by_GF*");
        } else {
             ossl_raise(rb_eArgError, "unknown argument, must be :GFp or :GF2m");
        }

        break;
    default:
        ossl_raise(rb_eArgError, "wrong number of arguments");
    }

    ASSUME(group);
    RTYPEDDATA_DATA(self) = group;

    return self;
}

static VALUE ossl_ec_group_get_asn1_flag(VALUE self)
{
    EC_GROUP *group = NULL;
    int flag;

    GetECGroup(self, group);
    flag = EC_GROUP_get_asn1_flag(group);

    return INT2NUM(flag);
}

static VALUE ossl_ec_group_set_asn1_flag(VALUE self, VALUE flag_v)
{
    EC_GROUP *group = NULL;

    GetECGroup(self, group);
    EC_GROUP_set_asn1_flag(group, NUM2INT(flag_v));

    return flag_v;
}

static VALUE ossl_ec_group_get_cofactor(VALUE self)
{
    VALUE bn_obj;
    BIGNUM *bn;
    EC_GROUP *group = NULL;

    GetECGroup(self, group);

    bn_obj = ossl_bn_new(NULL);
    bn = GetBNPtr(bn_obj);

    if (EC_GROUP_get_cofactor(group, bn, ossl_bn_ctx) != 1)
        ossl_raise(eEC_GROUP, "EC_GROUP_get_cofactor");

    return bn_obj;
}

static VALUE ossl_ec_group_get_curve_name(VALUE self)
{
    EC_GROUP *group = NULL;
    int nid;

    GetECGroup(self, group);
    if (group == NULL)
        return Qnil;

    nid = EC_GROUP_get_curve_name(group);

/* BUG: an nid or asn1 object should be returned, maybe. */
    return rb_str_new2(OBJ_nid2sn(nid));
}

static VALUE ossl_ec_group_get_degree(VALUE self)
{
    EC_GROUP *group = NULL;

    GetECGroup(self, group);

    return INT2NUM(EC_GROUP_get_degree(group));
}

static VALUE ossl_ec_group_eql(VALUE a, VALUE b)
{
    EC_GROUP *group1 = NULL, *group2 = NULL;

    GetECGroup(a, group1);
    GetECGroup(b, group2);

    switch (EC_GROUP_cmp(group1, group2, ossl_bn_ctx)) {
    case 0: return Qtrue;
    case 1: return Qfalse;
    default: ossl_raise(eEC_GROUP, "EC_GROUP_cmp");
    }
}

static VALUE ossl_ec_group_get_generator(VALUE self)
{
    EC_GROUP *group;
    const EC_POINT *generator;

    GetECGroup(self, group);
    generator = EC_GROUP_get0_generator(group);
    if (!generator)
        return Qnil;

    return ec_point_new(generator, group);
}

static VALUE
ossl_ec_group_initialize_copy(VALUE self, VALUE other)
{
    EC_GROUP *group, *group_new;

    TypedData_Get_Struct(self, EC_GROUP, &ossl_ec_group_type, group_new);
    if (group_new)
        ossl_raise(eEC_GROUP, "EC::Group already initialized");
    GetECGroup(other, group);

    group_new = EC_GROUP_dup(group);
    if (!group_new)
        ossl_raise(eEC_GROUP, "EC_GROUP_dup");
    RTYPEDDATA_DATA(self) = group_new;

    return self;
}

static VALUE ossl_ec_group_get_order(VALUE self)
{
    VALUE bn_obj;
    BIGNUM *bn;
    EC_GROUP *group = NULL;

    GetECGroup(self, group);

    bn_obj = ossl_bn_new(NULL);
    bn = GetBNPtr(bn_obj);

    if (EC_GROUP_get_order(group, bn, ossl_bn_ctx) != 1)
        ossl_raise(eEC_GROUP, "EC_GROUP_get_order");

    return bn_obj;
}

static VALUE ossl_ec_group_get_point_conversion_form(VALUE self)
{
    EC_GROUP *group = NULL;
    point_conversion_form_t form;
    VALUE ret;

    GetECGroup(self, group);
    form = EC_GROUP_get_point_conversion_form(group);

    switch (form) {
    case POINT_CONVERSION_UNCOMPRESSED: ret = ID_uncompressed; break;
    case POINT_CONVERSION_COMPRESSED:   ret = ID_compressed; break;
    case POINT_CONVERSION_HYBRID:       ret = ID_hybrid; break;
    default:    ossl_raise(eEC_GROUP, "unsupported point conversion form: %d, this module should be updated", form);
    }

   return ID2SYM(ret);
}

static VALUE
ossl_ec_group_set_point_conversion_form(VALUE self, VALUE form_v)
{
    EC_GROUP *group;
    point_conversion_form_t form;

    GetECGroup(self, group);
    form = parse_point_conversion_form_symbol(form_v);

    EC_GROUP_set_point_conversion_form(group, form);

    return form_v;
}

static VALUE ossl_ec_group_get_seed(VALUE self)
{
    EC_GROUP *group = NULL;
    size_t seed_len;

    GetECGroup(self, group);
    seed_len = EC_GROUP_get_seed_len(group);

    if (seed_len == 0)
        return Qnil;

    return rb_str_new((const char *)EC_GROUP_get0_seed(group), seed_len);
}

static VALUE ossl_ec_group_set_seed(VALUE self, VALUE seed)
{
    EC_GROUP *group = NULL;

    GetECGroup(self, group);
    StringValue(seed);

    if (EC_GROUP_set_seed(group, (unsigned char *)RSTRING_PTR(seed), RSTRING_LEN(seed)) != (size_t)RSTRING_LEN(seed))
        ossl_raise(eEC_GROUP, "EC_GROUP_set_seed");

    return seed;
}

static VALUE ossl_ec_group_set_generator(VALUE self, VALUE generator, VALUE order, VALUE cofactor)
{
    EC_GROUP *group = NULL;
    const EC_POINT *point;
    const BIGNUM *o, *co;

    GetECGroup(self, group);
    GetECPoint(generator, point);
    o = GetBNPtr(order);
    co = GetBNPtr(cofactor);

    if (EC_GROUP_set_generator(group, point, o, co) != 1)
        ossl_raise(eEC_GROUP, "EC_GROUP_set_generator");

    return self;
}

static VALUE ossl_ec_group_to_der(VALUE self)
{
    return ossl_ec_group_to_string(self, EXPORT_DER);
}

static VALUE ossl_ec_group_to_pem(VALUE self)
{
    return ossl_ec_group_to_string(self, EXPORT_PEM);
}

static VALUE ossl_ec_group_to_text(VALUE self)
{
    EC_GROUP *group;
    BIO *out;
    VALUE str;

    GetECGroup(self, group);
    if (!(out = BIO_new(BIO_s_mem()))) {
        ossl_raise(eEC_GROUP, "BIO_new(BIO_s_mem())");
    }
    if (!ECPKParameters_print(out, group, 0)) {
        BIO_free(out);
        ossl_raise(eEC_GROUP, NULL);
    }
    str = ossl_membio2str(out);

    return str;
}