Copyright (C) 2003,2004,2005 Daniel B. Cid <dcid@ossec.net>
  All rights reserved.
  This program is a free software; you can redistribute it
  and/or modify it under the terms of the GNU General Public
  License (version 2) as published by the FSF - Free Software 
  Foundation

OSSEC, os_xml library.
Available at http://www.ossec.net/c/os_xml/