content/browser/geolocation/wifi_data.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/browser/geolocation/wifi_data.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/logging.h"
  10
  11 namespace content {
  12
  13 AccessPointData::AccessPointData()
  14     : radio_signal_strength(kint32min),
  15       channel(kint32min),
  16       signal_to_noise(kint32min) {
  17 }
  18
  19 AccessPointData::~AccessPointData() {}
  20
  21 WifiData::WifiData() {}
  22
  23 WifiData::~WifiData() {}
  24
  25 bool WifiData::DiffersSignificantly(const WifiData& other) const {
  26   // More than 4 or 50% of access points added or removed is significant.
  27   static const size_t kMinChangedAccessPoints = 4;
  28   const size_t min_ap_count =
  29       std::min(access_point_data.size(), other.access_point_data.size());
  30   const size_t max_ap_count =
  31       std::max(access_point_data.size(), other.access_point_data.size());
  32   const size_t difference_threadhold = std::min(kMinChangedAccessPoints,
  33                                                 min_ap_count / 2);
  34   if (max_ap_count > min_ap_count + difference_threadhold)
  35     return true;
  36   // Compute size of intersection of old and new sets.
  37   size_t num_common = 0;
  38   for (AccessPointDataSet::const_iterator iter = access_point_data.begin();
  39        iter != access_point_data.end();
  40        iter++) {
  41     if (other.access_point_data.find(*iter) !=
  42         other.access_point_data.end()) {
  43       ++num_common;
  44     }
  45   }
  46   DCHECK(num_common <= min_ap_count);
  47
  48   // Test how many have changed.
  49   return max_ap_count > num_common + difference_threadhold;
  50 }
  51
  52 }  // namespace content