(Second attempt at http://codereview.chromium.org/553069/show)...

chrome/browser/geolocation/wifi_data_provider_osx.cc

Index: chrome/browser/geolocation/wifi_data_provider_osx.cc
===================================================================
--- chrome/browser/geolocation/wifi_data_provider_osx.cc	(revision 0)
+++ chrome/browser/geolocation/wifi_data_provider_osx.cc	(revision 0)
@@ -0,0 +1,168 @@
+// Copyright 2008, Google Inc.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+//  1. Redistributions of source code must retain the above copyright notice,
+//     this list of conditions and the following disclaimer.
+//  2. Redistributions in binary form must reproduce the above copyright notice,
+//     this list of conditions and the following disclaimer in the documentation
+//     and/or other materials provided with the distribution.
+//  3. Neither the name of Google Inc. nor the names of its contributors may be
+//     used to endorse or promote products derived from this software without
+//     specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+// WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+// EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+// OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+// OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+// ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// We use the OSX system API function WirelessScanSplit. This function is not
+// documented or included in the SDK, so we use a reverse-engineered header,
+// osx_wifi_.h. This file is taken from the iStumbler project
+// (http://www.istumbler.net).
+
+// TODO(cprince): remove platform-specific #ifdef guards when OS-specific
+// sources (e.g. WIN32_CPPSRCS) are implemented
+#ifdef OS_MACOSX
+
+#include "gears/geolocation/wifi_data_provider_osx.h"
+
+#include <dlfcn.h>
+#include <stdio.h>
+#include "gears/base/common/string_utils.h"
+#include "gears/geolocation/wifi_data_provider_common.h"
+
+// The time periods, in milliseconds, between successive polls of the wifi data.
+extern const int kDefaultPollingInterval = 120000;  // 2 mins
+extern const int kNoChangePollingInterval = 300000;  // 5 mins
+extern const int kTwoNoChangePollingInterval = 600000;  // 10 mins
+
+// static
+template<>
+WifiDataProviderImplBase *WifiDataProvider::DefaultFactoryFunction() {
+  return new OsxWifiDataProvider();
+}
+
+
+OsxWifiDataProvider::OsxWifiDataProvider() : is_first_scan_complete_(false) {
+  Start();
+}
+
+OsxWifiDataProvider::~OsxWifiDataProvider() {
+  stop_event_.Signal();
+  Join();
+}
+
+bool OsxWifiDataProvider::GetData(WifiData *data) {
+  assert(data);
+  MutexLock lock(&data_mutex_);
+  *data = wifi_data_;
+  // If we've successfully completed a scan, indicate that we have all of the
+  // data we can get.
+  return is_first_scan_complete_;
+}
+
+// Thread implementation
+void OsxWifiDataProvider::Run() {
+  void *apple_80211_library = dlopen(
+      "/System/Library/PrivateFrameworks/Apple80211.framework/Apple80211",
+      RTLD_LAZY);
+  if (!apple_80211_library) {
+    is_first_scan_complete_ = true;
+    return;
+  }
+
+  WirelessAttach_function_ = reinterpret_cast<WirelessAttachFunction>(
+      dlsym(apple_80211_library, "WirelessAttach"));
+  WirelessScanSplit_function_ = reinterpret_cast<WirelessScanSplitFunction>(
+      dlsym(apple_80211_library, "WirelessScanSplit"));
+  WirelessDetach_function_ = reinterpret_cast<WirelessDetachFunction>(
+      dlsym(apple_80211_library, "WirelessDetach"));
+  assert(WirelessAttach_function_ &&
+         WirelessScanSplit_function_ &&
+         WirelessDetach_function_);
+    
+  if ((*WirelessAttach_function_)(&wifi_context_, 0) != noErr) {
+    is_first_scan_complete_ = true;
+    return;
+  }
+
+  // Regularly get the access point data.
+  int polling_interval = kDefaultPollingInterval;
+  do {
+    WifiData new_data;
+    GetAccessPointData(&new_data.access_point_data);
+    bool update_available;
+    data_mutex_.Lock();
+    update_available = wifi_data_.DiffersSignificantly(new_data);
+    wifi_data_ = new_data;
+    data_mutex_.Unlock();
+    polling_interval =
+        UpdatePollingInterval(polling_interval, update_available);
+    if (update_available) {
+      is_first_scan_complete_ = true;
+      NotifyListeners();
+    }
+  } while (!stop_event_.WaitWithTimeout(polling_interval));
+
+  (*WirelessDetach_function_)(wifi_context_);
+
+  dlclose(apple_80211_library);
+}
+
+void OsxWifiDataProvider::GetAccessPointData(
+    WifiData::AccessPointDataSet *access_points) {
+  assert(access_points);
+  assert(WirelessScanSplit_function_);
+  CFArrayRef managed_access_points = NULL;
+  CFArrayRef adhoc_access_points = NULL;
+  if ((*WirelessScanSplit_function_)(wifi_context_,
+                                     &managed_access_points,
+                                     &adhoc_access_points,
+                                     0) != noErr) {
+    return;
+  }
+  
+  if (managed_access_points == NULL) {
+    return;
+  }
+
+  int num_access_points = CFArrayGetCount(managed_access_points);
+  for (int i = 0; i < num_access_points; ++i) {
+    const WirelessNetworkInfo *access_point_info =
+        reinterpret_cast<const WirelessNetworkInfo*>(
+        CFDataGetBytePtr(
+        reinterpret_cast<const CFDataRef>(
+        CFArrayGetValueAtIndex(managed_access_points, i))));
+        
+    // Currently we get only MAC address, signal strength, channel
+    // signal-to-noise and SSID
+    // TODO(steveblock): Work out how to get age.
+    AccessPointData access_point_data;
+    access_point_data.mac_address =
+        MacAddressAsString16(access_point_info->macAddress);
+    // WirelessNetworkInfo::signal appears to be signal strength in dBm.
+    access_point_data.radio_signal_strength = access_point_info->signal;
+    access_point_data.channel = access_point_info->channel;
+    // WirelessNetworkInfo::noise appears to be noise floor in dBm.
+    access_point_data.signal_to_noise = access_point_info->signal -
+                                        access_point_info->noise;
+    std::string16 ssid;
+    if (UTF8ToString16(reinterpret_cast<const char*>(access_point_info->name),
+                       access_point_info->nameLen,
+                       &ssid)) {
+      access_point_data.ssid = ssid;
+    }
+
+    access_points->insert(access_point_data);
+  }
+}
+
+#endif  // OS_MACOSX