Missing getGroupMembers from Remote API

i am missing a getGroupMembers from the remote api
which means i had to write it myself (see below)
but this take long time as my user list is growing
and will reach 2000 or more
a getGroupMembers will be so good for me
thanks

protected String[] getGroupMembers(String groupName) throws RemoteException {
ConfluenceSoapService soapService = getService();
String token = getToken();
if (!soapService.hasGroup(token, groupName))

ArrayList<String> users = new ArrayList<String>();
String[] activeUsers = soapService.getActiveUsers(token, true);
//TODO - this is what taking so long !! 30 sec and growing !!
for (String user : activeUsers) {
//get each user group list
String[] userGroups = soapService.getUserGroups(token, user);
for (String group : userGroups) {
if (group.equals(groupName))

}
}
return users.toArray(new String[users.size()]);
}