* call-seq:
 * conn.compare_ext(dn, attr, val, sctrls, cctrls)  => true or false
 * Compare the DN given as +dn+ to see whether it has the attribute +attr+
 * with a value of +val+. +sctrls+ is an array of server controls, whilst
 * +cctrls+ is an array of client controls.
rb_ldap_conn_compare_ext_s (VALUE self, VALUE dn, VALUE attr, VALUE val,
                            VALUE serverctrls, VALUE clientctrls)
  RB_LDAP_DATA *ldapdata;
  char *c_dn, *c_attr;
#ifdef USE_WLDAP32
  char *c_val;
  struct berval bval;
  LDAPControl **sctrls, **cctrls;

  GET_LDAP_DATA (self, ldapdata);
  c_dn = StringValueCStr (dn);
  c_attr = StringValueCStr (attr);
#ifdef USE_WLDAP32
  c_val = StringValueCStr (val);
  bval.bv_val = StringValueCStr (val);
  bval.bv_len = RSTRING (val)->len;
  sctrls = rb_ldap_get_controls (serverctrls);
  cctrls = rb_ldap_get_controls (clientctrls);

  ldapdata->err = ldap_compare_ext_s (ldapdata->ldap, c_dn, c_attr,
#ifdef USE_WLDAP32
                                      &bval, sctrls, cctrls);

  if ((ldapdata->err) == LDAP_COMPARE_TRUE)
    return Qtrue;
  else if ((ldapdata->err) == LDAP_COMPARE_FALSE)
    return Qfalse;

  Check_LDAP_Result (ldapdata->err);

  fprintf (stderr,
           "rb_ldap_conn_compare_ext_s() unexpectedly set no error.\n");

  return self;