class OpenSSL::X509::Attribute

static VALUE
ossl_x509attr_initialize(int argc, VALUE *argv, VALUE self)
{
    VALUE oid, value;
    X509_ATTRIBUTE *attr, *x;
    const unsigned char *p;

    GetX509Attr(self, attr);
    if(rb_scan_args(argc, argv, "11", &oid, &value) == 1){
        oid = ossl_to_der_if_possible(oid);
        StringValue(oid);
        p = (unsigned char *)RSTRING_PTR(oid);
        x = d2i_X509_ATTRIBUTE(&attr, &p, RSTRING_LEN(oid));
        DATA_PTR(self) = attr;
        if(!x){
            ossl_raise(eX509AttrError, NULL);
        }
        return self;
    }
    rb_funcall(self, rb_intern("oid="), 1, oid);
    rb_funcall(self, rb_intern("value="), 1, value);

    return self;
}

static VALUE
ossl_x509attr_get_oid(VALUE self)
{
    X509_ATTRIBUTE *attr;
    ASN1_OBJECT *oid;
    BIO *out;
    VALUE ret;
    int nid;

    GetX509Attr(self, attr);
    oid = X509_ATTRIBUTE_get0_object(attr);
    if ((nid = OBJ_obj2nid(oid)) != NID_undef)
        ret = rb_str_new2(OBJ_nid2sn(nid));
    else{
        if (!(out = BIO_new(BIO_s_mem())))
            ossl_raise(eX509AttrError, NULL);
        i2a_ASN1_OBJECT(out, oid);
        ret = ossl_membio2str(out);
    }

    return ret;
}

static VALUE
ossl_x509attr_set_oid(VALUE self, VALUE oid)
{
    X509_ATTRIBUTE *attr;
    ASN1_OBJECT *obj;
    char *s;

    GetX509Attr(self, attr);
    s = StringValueCStr(oid);
    obj = OBJ_txt2obj(s, 0);
    if(!obj) ossl_raise(eX509AttrError, NULL);
    if (!X509_ATTRIBUTE_set1_object(attr, obj)) {
        ASN1_OBJECT_free(obj);
        ossl_raise(eX509AttrError, "X509_ATTRIBUTE_set1_object");
    }
    ASN1_OBJECT_free(obj);

    return oid;
}

static VALUE
ossl_x509attr_to_der(VALUE self)
{
    X509_ATTRIBUTE *attr;
    VALUE str;
    int len;
    unsigned char *p;

    GetX509Attr(self, attr);
    if((len = i2d_X509_ATTRIBUTE(attr, NULL)) <= 0)
        ossl_raise(eX509AttrError, NULL);
    str = rb_str_new(0, len);
    p = (unsigned char *)RSTRING_PTR(str);
    if(i2d_X509_ATTRIBUTE(attr, &p) <= 0)
        ossl_raise(eX509AttrError, NULL);
    ossl_str_adjust(str, p);

    return str;
}

static VALUE
ossl_x509attr_get_value(VALUE self)
{
    X509_ATTRIBUTE *attr;
    STACK_OF(ASN1_TYPE) *sk;
    VALUE str;
    int i, count, len;
    unsigned char *p;

    GetX509Attr(self, attr);
    /* there is no X509_ATTRIBUTE_get0_set() :( */
    if (!(sk = sk_ASN1_TYPE_new_null()))
        ossl_raise(eX509AttrError, "sk_new");

    count = X509_ATTRIBUTE_count(attr);
    for (i = 0; i < count; i++)
        sk_ASN1_TYPE_push(sk, X509_ATTRIBUTE_get0_type(attr, i));

    if ((len = i2d_ASN1_SET_ANY(sk, NULL)) <= 0) {
        sk_ASN1_TYPE_free(sk);
        ossl_raise(eX509AttrError, NULL);
    }
    str = rb_str_new(0, len);
    p = (unsigned char *)RSTRING_PTR(str);
    if (i2d_ASN1_SET_ANY(sk, &p) <= 0) {
        sk_ASN1_TYPE_free(sk);
        ossl_raise(eX509AttrError, NULL);
    }
    ossl_str_adjust(str, p);
    sk_ASN1_TYPE_free(sk);

    return rb_funcall(mASN1, rb_intern("decode"), 1, str);
}

static VALUE
ossl_x509attr_set_value(VALUE self, VALUE value)
{
    X509_ATTRIBUTE *attr;
    VALUE asn1_value;
    int i, asn1_tag;

    OSSL_Check_Kind(value, cASN1Data);
    asn1_tag = NUM2INT(rb_attr_get(value, rb_intern("@tag")));
    asn1_value = rb_attr_get(value, rb_intern("@value"));
    if (asn1_tag != V_ASN1_SET)
        ossl_raise(eASN1Error, "argument must be ASN1::Set");
    if (!RB_TYPE_P(asn1_value, T_ARRAY))
        ossl_raise(eASN1Error, "ASN1::Set has non-array value");

    GetX509Attr(self, attr);
    if (X509_ATTRIBUTE_count(attr)) { /* populated, reset first */
        ASN1_OBJECT *obj = X509_ATTRIBUTE_get0_object(attr);
        X509_ATTRIBUTE *new_attr = X509_ATTRIBUTE_create_by_OBJ(NULL, obj, 0, NULL, -1);
        if (!new_attr)
            ossl_raise(eX509AttrError, NULL);
        SetX509Attr(self, new_attr);
        X509_ATTRIBUTE_free(attr);
        attr = new_attr;
    }

    for (i = 0; i < RARRAY_LEN(asn1_value); i++) {
        ASN1_TYPE *a1type = ossl_asn1_get_asn1type(RARRAY_AREF(asn1_value, i));
        if (!X509_ATTRIBUTE_set1_data(attr, ASN1_TYPE_get(a1type),
                                      a1type->value.ptr, -1)) {
            ASN1_TYPE_free(a1type);
            ossl_raise(eX509AttrError, NULL);
        }
        ASN1_TYPE_free(a1type);
    }

    return value;
}