navfilterex-pseudo-container.cpp

Pseudo-code example of using a container of application data structures for storing the navigation messages processed by the filter.

//==============================================================================
//
//  This file is part of GNSSTk, the ARL:UT GNSS Toolkit.
//
//  The GNSSTk is free software; you can redistribute it and/or modify
//  it under the terms of the GNU Lesser General Public License as published
//  by the Free Software Foundation; either version 3.0 of the License, or
//  any later version.
//
//  The GNSSTk is distributed in the hope that it will be useful,
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//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public
//  License along with GNSSTk; if not, write to the Free Software Foundation,
//  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110, USA
//
//  This software was developed by Applied Research Laboratories at the
//  University of Texas at Austin.
//  Copyright 2004-2022, The Board of Regents of The University of Texas System
//
//==============================================================================
 
//==============================================================================
//
//  This software was developed by Applied Research Laboratories at the
//  University of Texas at Austin, under contract to an agency or agencies
//  within the U.S. Department of Defense. The U.S. Government retains all
//  rights to use, duplicate, distribute, disclose, or release this software.
//
//  Pursuant to DoD Directive 523024
//
//  DISTRIBUTION STATEMENT A: This software has been approved for public
//                            release, distribution is unlimited.
//
//==============================================================================
 
class NavSubframe
{
public:
   std::vector<uint32_t> subframe;
};
 
typedef std::list<NavSubframe*> NavSubframeList;
 
void readNavEpoch(NavSubframeList& nsl)
{
   NavSubframe *nsf;
   while (sameEpoch)
   {
      nsf = new NavSubframe();
      strm >> *nsf;
      if (strm)
         nsl.push_back(nsf);
   }
}
 
void filterEX()
{
      // Filter manager, where the work is done
   gnsstk::NavFilterMgr mgr;
      // Individual filters being applied
   gnsstk::LNavCookFilter filtCook;
   gnsstk::LNavParityFilter filtParity;
      // Data being passed to the filter
   gnsstk::LNavFilterData navFiltData;
   gnsstk::NavFilter::NavMsgList::const_iterator nmli;
      // application's nav storage
   NavSubframeList nsl;
   NavSubframeList::iterator nsli;
 
      // Tell the manager what filters to use
   mgr.addFilter(&filtCook);
   mgr.addFilter(&filtParity);
 
   while (strm)
   {
      readNavEpoch(nsl);
 
         // process each subframe read from the input stream
      for (nsli = nsl.begin(); nsli != nsl.end(); nsli++)
      {
         NavSubframe *nsf = *nsli;
            // Point the filter data to the LNAV message
         navFiltData.sf = &nsf->subframe[1];
 
            // validate the subframe
         gnsstk::NavFilter::NavMsgList l = mgr.validate(&navFiltData);
 
            // process the results
         for (nmli = l.begin(); nmli != l.end(); nmli++)
         {
            gnsstk::LNavFilterData *fd =
               dynamic_cast<gnsstk::LNavFilterData*>(*nmli);
               // do something with fd (nav message that passed the filters)
         }
            // Because the filters are depth 1, we can immediately
            // free the application data storage.  We set the value in
            // the list to NULL as "good practice".  Erase the list at
            // the end so that we don't end up doing any weird
            // unnecessary memory management internal to the list
            // implementation.
         delete nsf;
         *nsli = NULL;
      }
      nsl.clear();
   }
 
      // Finalize the filters.  Probably not necessary when using only
      // depth 1 filters, but good practice in any case.
   gnsstk::NavFilter::NavMsgList l = mgr.finalize();
 
      // process the results
   for (nmli = l.begin(); nmli != l.end(); nmli++)
   {
      gnsstk::LNavFilterData *fd =
         dynamic_cast<gnsstk::LNavFilterData*>(*nmli);
         // do something with fd (nav message that passed the filters)
   }
}