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);
    rb_str_set_len(str, p - (unsigned char*)RSTRING_PTR(str));

    return str;
}

static VALUE
ossl_x509attr_get_value(VALUE self)
{
    X509_ATTRIBUTE *attr;
    VALUE str, asn1;
    long length;
    unsigned char *p;

    GetX509Attr(self, attr);
    if(attr->value.ptr == NULL) return Qnil;
    if(OSSL_X509ATTR_IS_SINGLE(attr)){
        length = i2d_ASN1_TYPE(attr->value.single, NULL);
        str = rb_str_new(0, length);
        p = (unsigned char *)RSTRING_PTR(str);
        i2d_ASN1_TYPE(attr->value.single, &p);
        ossl_str_adjust(str, p);
    }
    else{
        length = i2d_ASN1_SET_OF_ASN1_TYPE(attr->value.set,
                        (unsigned char **) NULL, i2d_ASN1_TYPE,
                        V_ASN1_SET, V_ASN1_UNIVERSAL, 0);
        str = rb_str_new(0, length);
        p = (unsigned char *)RSTRING_PTR(str);
        i2d_ASN1_SET_OF_ASN1_TYPE(attr->value.set, &p,
                        i2d_ASN1_TYPE, V_ASN1_SET, V_ASN1_UNIVERSAL, 0);
        ossl_str_adjust(str, p);
    }
    asn1 = rb_funcall(mASN1, rb_intern("decode"), 1, str);

    return asn1;
}

static VALUE
ossl_x509attr_set_value(VALUE self, VALUE value)
{
    X509_ATTRIBUTE *attr;
    ASN1_TYPE *a1type;

    if(!(a1type = ossl_asn1_get_asn1type(value)))
        ossl_raise(eASN1Error, "could not get ASN1_TYPE");
    if(ASN1_TYPE_get(a1type) == V_ASN1_SEQUENCE){
        ASN1_TYPE_free(a1type);
        ossl_raise(eASN1Error, "couldn't set SEQUENCE for attribute value.");
    }
    GetX509Attr(self, attr);
    if(attr->value.set){
        if(OSSL_X509ATTR_IS_SINGLE(attr)) ASN1_TYPE_free(attr->value.single);
        else sk_ASN1_TYPE_free(attr->value.set);
    }
    OSSL_X509ATTR_SET_SINGLE(attr);
    attr->value.single = a1type;

    return value;
}