owlps/owlps-positioner/src/measurement.cc

/*
 * This file is part of the Owl Positioning System (OwlPS).
 * OwlPS is a project of the University of Franche-Comté
 * (Université de Franche-Comté), France.
 */


#include "measurement.hh"
#include "posexcept.hh"

#include <iostream>
#include <sstream>

using namespace std ;



/* *** Constructors *** */


/**
 * Note that values pointed by #ap are not deleted.
 */
Measurement::~Measurement()
{
  ss_list.clear() ;
}



/* *** Write accessors *** */


/**
 * @param packet_id The sequence number of the packet in the request,
 * as sent by the mobile.
 * @param ss_dbm The signal strength to add to #ss_list (in dBm).
 */
void Measurement::
add_ss(const pkt_id_t packet_id, const ss_t ss_dbm)
{
  unsigned int ss_list_size = ss_list.size() ;

  // Add the new value (in dBm) along with the packet identifier:
  pair<pkt_id_t, ss_t> packet(make_pair(packet_id, ss_dbm)) ;
  if (! ss_list.insert(packet).second)
    {
      cerr
          << "Cannot insert the packet (#" << packet_id << ", "
          << static_cast<int_fast16_t>(ss_dbm) << " dBm)\n" ;
      return ;
    }

  // Update the average with the new value
  double total_ss_mwatts =
    pow(10, static_cast<double>(ss_dbm) / 10.0) + // New SS in mW
    (ss_list_size * pow(10, average_ss / 10.0)) ; // Other values in mW
  // Convert the average back in dBm:
  average_ss = 10.0 * log10(total_ss_mwatts / ss_list.size()) ;
}


/**
 * Add an SS list to the current Measurement's SS list.
 * If the new SS list contains a packet with the same ID, the old one
 * is overwritten.
 */
void Measurement::
add_ss_list(const map<pkt_id_t, ss_t> &_ss_list)
{
  // We cannot use insert() here because we want to overwrite the
  // previous values with the same ID, if any.
  for (map<pkt_id_t, ss_t>::const_iterator
       i = _ss_list.begin() ; i != _ss_list.end() ; ++i)
    ss_list[i->first] = i->second ;

  update_average_ss() ;
}


/**
 * Merge consists of adding the SS values of \em source to #ss_list. It
 * is possible only if the #ap of the two Measurement are identical.
 * @throw cannot_merge if the AP of the two Measurement are different.
 */
void Measurement::merge(const Measurement &source)
{
  if (ap != source.ap)
    throw cannot_merge(
      "error when trying to merge measurements, APs are different") ;

  add_ss_list(source.ss_list) ;
}


/**
 * - #ap is not deleted, only initialised to NULL.
 * - #ss_list is cleared.
 * - #average_ss is initialised to 0.
 */
void Measurement::clear()
{
  ss_list.clear() ;
  average_ss = 0 ;
  ap = NULL ;
}



/* *** Operations *** */


void Measurement::update_average_ss()
{
  if (ss_list.empty())
    {
      average_ss = 0 ;
      return ;
    }

  double total_ss_mwatts = 0 ;

  for (map<pkt_id_t, ss_t>::const_iterator
       i = ss_list.begin() ; i != ss_list.end() ; ++i)
    // Add the current value in mW to the total
    total_ss_mwatts += pow(10, static_cast<double>(i->second) / 10.0) ;

  // Compute the average in mW and convert it to dBm
  average_ss = 10 * log10(total_ss_mwatts / ss_list.size()) ;
}



/* *** Operators *** */


Measurement& Measurement::operator=(const Measurement &m)
{
  if (this == &m)
    return *this ;

  ap = m.ap ;
  ss_list = m.ss_list ;
  average_ss = m.average_ss ;

  return *this ;
}


bool Measurement::operator==(const Measurement &m) const
{
  if (this == &m)
    return true ;

  return
    ap == m.ap &&
    ss_list == m.ss_list &&
    average_ss == m.average_ss ;
}



const string Measurement::to_csv() const
{
  ostringstream csv_line ;

  if (ss_list.empty())
    return "" ;

  string mac_ap("") ;
  if (ap)
    mac_ap = ap->get_mac_addr() ;

  for (map<pkt_id_t, ss_t>::const_iterator
       i = ss_list.begin() ; i != ss_list.end() ; ++i)
    {
      if (i != ss_list.begin())
        csv_line << ';' ;
      csv_line
          << mac_ap << ';'
          << i->first << ';'
          << static_cast<int_fast16_t>(i->second) ;
    }

  return csv_line.str() ;
}



ostream &operator<<(ostream &os, const Measurement &m)
{
  // MAC address
  os
      << "AP: " << (m.ap ? m.ap->get_mac_addr() : "Unknown_AP")
      << ": " ;

  // List of SS
  if (m.ss_list.empty())
    os << "No values" ;
  else
    for (map<pkt_id_t, ss_t>::const_iterator
         i = m.ss_list.begin() ; i != m.ss_list.end() ; ++i)
      {
        if (i != m.ss_list.begin())
          os << ';' ;
        os << static_cast<int_fast16_t>(i->second)
           << '(' << i->first << ')' ;
      }
  os << " [AVG=" << m.average_ss << "]" ;

  return os ;
}