Gears Android WIFI/基站定位源代码分析

文章出处：http://www.limodev.cn/blog
作者联系方式：李先静 <xianjimli at hotmail dot com>

Broncho A1还不支持基站和WIFI定位，Android的老版本里是有NetworkLocationProvider的，它实现了基站和WIFI定位，但从 android 1.5之后就被移除了。本来想在broncho A1里自己实现NetworkLocationProvider的，但一直没有时间去研究。我知道 gears(http://code.google.com/p/gears/)是有提供类似的功能，昨天研究了一下Gears的代码，看能不能移植到 android中来。
1.下载源代码
[url]svn checkout http://gears.googlecode.com/svn/trunk/ gears-read-only[/url]

定位相关的源代码在gears/geolocation目录中。

2.关注android平台中的基站位置变化。

JAVA类AndroidRadioDataProvider是 PhoneStateListener的子类，用来监听Android电话的状态变化。当服务状态、信号强度和基站变化时，就会用下面代码获取小区信息：

Java代码

1. RadioDataradioData=newRadioData();
2. GsmCellLocationgsmCellLocation=(GsmCellLocation)cellLocation;
4. //Extractthecellid,LAC,andsignalstrength.
5. radioData.cellId=gsmCellLocation.getCid();
6. radioData.locationAreaCode=gsmCellLocation.getLac();
7. radioData.signalStrength=signalStrength;
9. //ExtractthehomeMCCandhomeMNC.
10. Stringoperator=telephonyManager.getSimOperator();
11. radioData.setMobileCodes(operator,true);
13. if(serviceState!=null){
14. //Extractthecarriername.
15. radioData.carrierName=serviceState.getOperatorAlphaLong();
17. //ExtracttheMCCandMNC.
18. operator=serviceState.getOperatorNumeric();
19. radioData.setMobileCodes(operator,false);
20. }
22. //Finallygettheradiotype.
23. inttype=telephonyManager.getNetworkType();
24. if(type==TelephonyManager.NETWORK_TYPE_UMTS){
25. radioData.radioType=RADIO_TYPE_WCDMA;
26. }elseif(type==TelephonyManager.NETWORK_TYPE_GPRS
27. ||type==TelephonyManager.NETWORK_TYPE_EDGE){
28. radioData.radioType=RADIO_TYPE_GSM;
29. }

RadioData radioData = new RadioData();
      GsmCellLocation gsmCellLocation = (GsmCellLocation) cellLocation;
 
      // Extract the cell id, LAC, and signal strength.
      radioData.cellId = gsmCellLocation.getCid();
      radioData.locationAreaCode = gsmCellLocation.getLac();
      radioData.signalStrength = signalStrength;
 
      // Extract the home MCC and home MNC.
      String operator = telephonyManager.getSimOperator();
      radioData.setMobileCodes(operator, true);
 
      if (serviceState != null) {
        // Extract the carrier name.
        radioData.carrierName = serviceState.getOperatorAlphaLong();
 
        // Extract the MCC and MNC.
        operator = serviceState.getOperatorNumeric();
        radioData.setMobileCodes(operator, false);
      }
 
      // Finally get the radio type.
      int type = telephonyManager.getNetworkType();
      if (type == TelephonyManager.NETWORK_TYPE_UMTS) {
        radioData.radioType = RADIO_TYPE_WCDMA;
      } else if (type == TelephonyManager.NETWORK_TYPE_GPRS
                 || type == TelephonyManager.NETWORK_TYPE_EDGE) {
        radioData.radioType = RADIO_TYPE_GSM;
      }

然后调用用C代码实现的onUpdateAvailable函数。

2.Native函数onUpdateAvailable是在 radio_data_provider_android.cc里实现的。

声明Native函数

Java代码

1. JNINativeMethodAndroidRadioDataProvider::native_methods_[]={
2. {"onUpdateAvailable",
3. "(L"GEARS_JAVA_PACKAGE"/AndroidRadioDataProvider$RadioData;J)V",
4. reinterpret_cast<void*>(AndroidRadioDataProvider::OnUpdateAvailable)
5. },
6. };

JNINativeMethod AndroidRadioDataProvider::native_methods_[] = {
  {"onUpdateAvailable",
   "(L" GEARS_JAVA_PACKAGE "/AndroidRadioDataProvider$RadioData;J)V",
   reinterpret_cast<void*>(AndroidRadioDataProvider::OnUpdateAvailable)
  },
};

JNI调用好像只能调用静态成员函数，把对象本身用一个参数传进来，然后再调用对象的成员函数。

Java代码

1. voidAndroidRadioDataProvider::OnUpdateAvailable(JNIEnv*env,
2. jclasscls,
3. jobjectradio_data,
4. jlongself){
5. assert(radio_data);
6. assert(self);
7. AndroidRadioDataProvider*self_ptr=
8. reinterpret_cast<AndroidRadioDataProvider*>(self);
9. RadioDatanew_radio_data;
10. if(InitFromJavaRadioData(env,radio_data,&new_radio_data)){
11. self_ptr->NewRadioDataAvailable(&new_radio_data);
12. }
13. }

void AndroidRadioDataProvider::OnUpdateAvailable(JNIEnv* env,
                                                 jclass cls,
                                                 jobject radio_data,
                                                 jlong self) {
  assert(radio_data);
  assert(self);
  AndroidRadioDataProvider *self_ptr =
      reinterpret_cast<AndroidRadioDataProvider*>(self);
  RadioData new_radio_data;
  if (InitFromJavaRadioData(env, radio_data, &new_radio_data)) {
    self_ptr->NewRadioDataAvailable(&new_radio_data);
  }
}

先判断基站信息有没有变化，如果有变化则通知相关的监听者。

Java代码

1. voidAndroidRadioDataProvider::NewRadioDataAvailable(
2. RadioData*new_radio_data){
3. boolis_update_available=false;
4. data_mutex_.Lock();
5. if(new_radio_data&&!radio_data_.Matches(*new_radio_data)){
6. radio_data_=*new_radio_data;
7. is_update_available=true;
8. }
9. //Avoidholdingthemutexlockedwhilenotifyingobservers.
10. data_mutex_.Unlock();
12. if(is_update_available){
13. NotifyListeners();
14. }
15. }

void AndroidRadioDataProvider::NewRadioDataAvailable(
    RadioData* new_radio_data) {
  bool is_update_available = false;
  data_mutex_.Lock();
  if (new_radio_data && !radio_data_.Matches(*new_radio_data)) {
    radio_data_ = *new_radio_data;
    is_update_available = true;
  }
  // Avoid holding the mutex locked while notifying observers.
  data_mutex_.Unlock();
 
  if (is_update_available) {
    NotifyListeners();
  }
}

接下来的过程，基站定位和WIFI定位是一样的，后面我们再来介绍。下面我们先看 WIFI定位。

3.关注android平台中的WIFI变化。

JAVA类AndroidWifiDataProvider扩展了 BroadcastReceiver类，它关注WIFI扫描结果:

Java代码

1. IntentFilterfilter=newIntentFilter();
2. filter.addAction(mWifiManager.SCAN_RESULTS_AVAILABLE_ACTION);
3. mContext.registerReceiver(this,filter,null,handler);

IntentFilter filter = new IntentFilter();
    filter.addAction(mWifiManager.SCAN_RESULTS_AVAILABLE_ACTION);
    mContext.registerReceiver(this, filter, null, handler);

当收到WIFI扫描结果后，调用Native函数 onUpdateAvailable，并把WIFI的扫描结果传递过去。

Java代码

1. publicvoidonReceive(Contextcontext,Intentintent){
2. if(intent.getAction().equals(
3. mWifiManager.SCAN_RESULTS_AVAILABLE_ACTION)){
4. if(Config.LOGV){
5. Log.v(TAG,"Wifiscanresulstavailable");
6. }
7. onUpdateAvailable(mWifiManager.getScanResults(),mNativeObject);
8. }
9. }

 public void onReceive(Context context, Intent intent) {
    if (intent.getAction().equals(
            mWifiManager.SCAN_RESULTS_AVAILABLE_ACTION)) {
      if (Config.LOGV) {
        Log.v(TAG, "Wifi scan resulst available");
      }
      onUpdateAvailable(mWifiManager.getScanResults(), mNativeObject);
    }
  }

4.Native函数onUpdateAvailable是在 wifi_data_provider_android.cc里实现的。

Java代码

1. JNINativeMethodAndroidWifiDataProvider::native_methods_[]={
2. {"onUpdateAvailable",
3. "(Ljava/util/List;J)V",
4. reinterpret_cast<void*>(AndroidWifiDataProvider::OnUpdateAvailable)
5. },
6. };
8. voidAndroidWifiDataProvider::OnUpdateAvailable(JNIEnv*/*env*/,
9. jclass/*cls*/,
10. jobjectwifi_data,
11. jlongself){
12. assert(self);
13. AndroidWifiDataProvider*self_ptr=
14. reinterpret_cast<AndroidWifiDataProvider*>(self);
15. WifiDatanew_wifi_data;
16. if(wifi_data){
17. InitFromJava(wifi_data,&new_wifi_data);
18. }
19. //Wenotifyregardlessofwhethernew_wifi_dataisempty
20. //ornot.Thearbitratorwilldecidewhattodowithanempty
21. //WifiDataobject.
22. self_ptr->NewWifiDataAvailable(&new_wifi_data);
23. }
25. voidAndroidWifiDataProvider::NewWifiDataAvailable(WifiData*new_wifi_data){
26. assert(supported_);
27. assert(new_wifi_data);
28. boolis_update_available=false;
29. data_mutex_.Lock();
30. is_update_available=wifi_data_.DiffersSignificantly(*new_wifi_data);
31. wifi_data_=*new_wifi_data;
32. //Avoidholdingthemutexlockedwhilenotifyingobservers.
33. data_mutex_.Unlock();
35. if(is_update_available){
36. is_first_scan_complete_=true;
37. NotifyListeners();
38. }
40. #ifUSING_CCTESTS
41. //ThisisneededforrunningtheWiFitestontheemulator.
42. //Seewifi_data_provider_android.hfordetails.
43. if(!first_callback_made_&&wifi_data_.access_point_data.empty()){
44. first_callback_made_=true;
45. NotifyListeners();
46. }
47. #endif
48. }

JNINativeMethod AndroidWifiDataProvider::native_methods_[] = {
  {"onUpdateAvailable",
   "(Ljava/util/List;J)V",
   reinterpret_cast<void*>(AndroidWifiDataProvider::OnUpdateAvailable)
  },
};
 
void AndroidWifiDataProvider::OnUpdateAvailable(JNIEnv*  /* env */,
                                                jclass  /* cls */,
                                                jobject wifi_data,
                                                jlong self) {
  assert(self);
  AndroidWifiDataProvider *self_ptr =
      reinterpret_cast<AndroidWifiDataProvider*>(self);
  WifiData new_wifi_data;
  if (wifi_data) {
    InitFromJava(wifi_data, &new_wifi_data);
  }
  // We notify regardless of whether new_wifi_data is empty
  // or not. The arbitrator will decide what to do with an empty
  // WifiData object.
  self_ptr->NewWifiDataAvailable(&new_wifi_data);
}
 
void AndroidWifiDataProvider::NewWifiDataAvailable(WifiData* new_wifi_data) {
  assert(supported_);
  assert(new_wifi_data);
  bool is_update_available = false;
  data_mutex_.Lock();
  is_update_available = wifi_data_.DiffersSignificantly(*new_wifi_data);
  wifi_data_ = *new_wifi_data;
  // Avoid holding the mutex locked while notifying observers.
  data_mutex_.Unlock();
 
  if (is_update_available) {
    is_first_scan_complete_ = true;
    NotifyListeners();
  }
 
#if USING_CCTESTS
  // This is needed for running the WiFi test on the emulator.
  // See wifi_data_provider_android.h for details.
  if (!first_callback_made_ && wifi_data_.access_point_data.empty()) {
    first_callback_made_ = true;
    NotifyListeners();
  }
#endif
}

从以上代码可以看出，WIFI定位和基站定位的逻辑差不多，只是前者获取的WIFI的扫描结果，而后者获取的基站信息。后面代码的基本上就统一起来了，接下来我们继续看。

5.把变化(WIFI/基站）通知给相应的监听者。

Java代码

1. AndroidWifiDataProvider和AndroidRadioDataProvider都是继承了DeviceDataProviderImplBase，DeviceDataProviderImplBase的主要功能就是管理所有Listeners。
3. staticDeviceDataProvider*Register(ListenerInterface*listener){
4. MutexLockmutex(&instance_mutex_);
5. if(!instance_){
6. instance_=newDeviceDataProvider();
7. }
8. assert(instance_);
9. instance_->Ref();
10. instance_->AddListener(listener);
11. returninstance_;
12. }
14. staticboolUnregister(ListenerInterface*listener){
15. MutexLockmutex(&instance_mutex_);
16. if(!instance_->RemoveListener(listener)){
17. returnfalse;
18. }
19. if(instance_->Unref()){
20. deleteinstance_;
21. instance_=NULL;
22. }
23. returntrue;
24. }

AndroidWifiDataProvider和AndroidRadioDataProvider都是继承了DeviceDataProviderImplBase，DeviceDataProviderImplBase的主要功能就是管理所有Listeners。
 
  static DeviceDataProvider *Register(ListenerInterface *listener) {
    MutexLock mutex(&instance_mutex_);
    if (!instance_) {
      instance_ = new DeviceDataProvider();
    }
    assert(instance_);
    instance_->Ref();
    instance_->AddListener(listener);
    return instance_;
  }
 
  static bool Unregister(ListenerInterface *listener) {
    MutexLock mutex(&instance_mutex_);
    if (!instance_->RemoveListener(listener)) {
      return false;
    }
    if (instance_->Unref()) {
      delete instance_;
      instance_ = NULL;
    }
    return true;
  }

6.谁在监听变化(WIFI/基站）

NetworkLocationProvider在监听变化(WIFI/基站）:

Java代码

1. radio_data_provider_=RadioDataProvider::Register(this);
2. wifi_data_provider_=WifiDataProvider::Register(this);

radio_data_provider_ = RadioDataProvider::Register(this);
  wifi_data_provider_ = WifiDataProvider::Register(this);

当有变化时，会调用函数DeviceDataUpdateAvailable：

Java代码

1. //DeviceDataProviderInterface::ListenerInterfaceimplementation.
2. voidNetworkLocationProvider::DeviceDataUpdateAvailable(
3. RadioDataProvider*provider){
4. MutexLocklock(&data_mutex_);
5. assert(provider==radio_data_provider_);
6. is_radio_data_complete_=radio_data_provider_->GetData(&radio_data_);
8. DeviceDataUpdateAvailableImpl();
9. }
11. voidNetworkLocationProvider::DeviceDataUpdateAvailable(
12. WifiDataProvider*provider){
13. assert(provider==wifi_data_provider_);
14. MutexLocklock(&data_mutex_);
15. is_wifi_data_complete_=wifi_data_provider_->GetData(&wifi_data_);
17. DeviceDataUpdateAvailableImpl();
18. }

// DeviceDataProviderInterface::ListenerInterface implementation.
void NetworkLocationProvider::DeviceDataUpdateAvailable(
    RadioDataProvider *provider) {
  MutexLock lock(&data_mutex_);
  assert(provider == radio_data_provider_);
  is_radio_data_complete_ = radio_data_provider_->GetData(&radio_data_);
 
  DeviceDataUpdateAvailableImpl();
}
 
void NetworkLocationProvider::DeviceDataUpdateAvailable(
    WifiDataProvider *provider) {
  assert(provider == wifi_data_provider_);
  MutexLock lock(&data_mutex_);
  is_wifi_data_complete_ = wifi_data_provider_->GetData(&wifi_data_);
 
  DeviceDataUpdateAvailableImpl();
}

无论是WIFI还是基站变化，最后都会调用 DeviceDataUpdateAvailableImpl：

Java代码

1. voidNetworkLocationProvider::DeviceDataUpdateAvailableImpl(){
2. timestamp_=GetCurrentTimeMillis();
4. //Signaltotheworkerthreadthatnewdataisavailable.
5. is_new_data_available_=true;
6. thread_notification_event_.Signal();
7. }

void NetworkLocationProvider::DeviceDataUpdateAvailableImpl() {
  timestamp_ = GetCurrentTimeMillis();
 
  // Signal to the worker thread that new data is available.
  is_new_data_available_ = true;
  thread_notification_event_.Signal();
}

这里面只是发了一个signal，通知另外一个线程去处理。

7.谁在等待thread_notification_event_

线程函数NetworkLocationProvider::Run在一个循环中等待 thread_notification_event，当有变化(WIFI/基站）时，就准备请求服务器查询位置。

先等待：

Java代码

1. if(remaining_time>0){
2. thread_notification_event_.WaitWithTimeout(
3. static_cast<int>(remaining_time));
4. }else{
5. thread_notification_event_.Wait();
6. }

if (remaining_time > 0) {
      thread_notification_event_.WaitWithTimeout(
          static_cast<int>(remaining_time));
    } else {
      thread_notification_event_.Wait();
    }

准备请求：

Java代码

1. if(make_request){
2. MakeRequest();
3. remaining_time=1;
4. }

    if (make_request) {
      MakeRequest();
      remaining_time = 1;
    }

再来看MakeRequest的实现：

先从cache中查找位置：

Java代码

1. constPosition*cached_position=
2. position_cache_->FindPosition(radio_data_,wifi_data_);
3. data_mutex_.Unlock();
4. if(cached_position){
5. assert(cached_position->IsGoodFix());
6. //Recordthepositionandupdateitstimestamp.
7. position_mutex_.Lock();
8. position_=*cached_position;
9. position_.timestamp=timestamp_;
10. position_mutex_.Unlock();
12. //Letlistenersknowthatwenowhaveapositionavailable.
13. UpdateListeners();
14. returntrue;
15. }

 const Position *cached_position =
      position_cache_->FindPosition(radio_data_, wifi_data_);
  data_mutex_.Unlock();
  if (cached_position) {
    assert(cached_position->IsGoodFix());
    // Record the position and update its timestamp.
    position_mutex_.Lock();
    position_ = *cached_position;
    position_.timestamp = timestamp_;
    position_mutex_.Unlock();
 
    // Let listeners know that we now have a position available.
    UpdateListeners();
    return true;
  }

如果找不到，再做实际的请求

Java代码

1. returnrequest_->MakeRequest(access_token,
2. radio_data_,
3. wifi_data_,
4. request_address_,
5. address_language_,
6. kBadLatLng,//Wedon'thaveapositiontopass
7. kBadLatLng,//totheserver.
8. timestamp_);

  return request_->MakeRequest(access_token,
                               radio_data_,
                               wifi_data_,
                               request_address_,
                               address_language_,
                               kBadLatLng,  // We don't have a position to pass
                               kBadLatLng,  // to the server.
                               timestamp_);

7.客户端协议包装

前面的request_是NetworkLocationRequest实例，先看 MakeRequest的实现：

先对参数进行打包：

Java代码

1. if(!FormRequestBody(host_name_,access_token,radio_data,wifi_data,
2. request_address,address_language,latitude,longitude,
3. is_reverse_geocode_,&post_body_)){
4. returnfalse;
5. }

  if (!FormRequestBody(host_name_, access_token, radio_data, wifi_data,
                       request_address, address_language, latitude, longitude,
                       is_reverse_geocode_, &post_body_)) {
    return false;
  }

通知负责收发的线程

Java代码

1. thread_event_.Signal();

  thread_event_.Signal();

8.负责收发的线程

Java代码

1. voidNetworkLocationRequest::Run(){
2. while(true){
3. thread_event_.Wait();
4. if(is_shutting_down_){
5. break;
6. }
7. MakeRequestImpl();
8. }
9. }
11. voidNetworkLocationRequest::MakeRequestImpl(){
12. WebCacheDB::PayloadInfopayload;

void NetworkLocationRequest::Run() {
  while (true) {
    thread_event_.Wait();
    if (is_shutting_down_) {
      break;
    }
    MakeRequestImpl();
  }
}
 
void NetworkLocationRequest::MakeRequestImpl() {
  WebCacheDB::PayloadInfo payload;

把打包好的数据通过HTTP请求，发送给服务器

Java代码

1. scoped_refptr<BlobInterface>payload_data;
2. boolresult=HttpPost(url_.c_str(),
3. false,//Notcapturing,sofollowredirects
4. NULL,//reason_header_value
5. HttpConstants::kMimeApplicationJson,//Content-Type
6. NULL,//mod_since_date
7. NULL,//required_cookie
8. true,//disable_browser_cookies
9. post_body_.get(),
10. &payload,
11. &payload_data,
12. NULL,//was_redirected
13. NULL,//full_redirect_url
14. NULL);//error_message
16. MutexLocklock(&is_processing_response_mutex_);
17. //is_aborted_maybetrueevenifHttpPostsucceeded.
18. if(is_aborted_){
19. LOG(("NetworkLocationRequest::Run():HttpPostrequestwascancelled.\n"));
20. return;
21. }
22. if(listener_){
23. Positionposition;
24. std::stringresponse_body;
25. if(result){
26. //IfHttpPostsucceeded,payload_dataisguaranteedtobenon-NULL.
27. assert(payload_data.get());
28. if(!payload_data->Length()||
29. !BlobToString(payload_data.get(),&response_body)){
30. LOG(("NetworkLocationRequest::Run():Failedtogetresponsebody.\n"));
31. }
32. }

 scoped_refptr<BlobInterface> payload_data;
  bool result = HttpPost(url_.c_str(),
                         false,            // Not capturing, so follow redirects
                         NULL,             // reason_header_value
                         HttpConstants::kMimeApplicationJson,  // Content-Type
                         NULL,             // mod_since_date
                         NULL,             // required_cookie
                         true,             // disable_browser_cookies
                         post_body_.get(),
                         &payload,
                         &payload_data,
                         NULL,             // was_redirected
                         NULL,             // full_redirect_url
                         NULL);            // error_message
 
  MutexLock lock(&is_processing_response_mutex_);
  // is_aborted_ may be true even if HttpPost succeeded.
  if (is_aborted_) {
    LOG(("NetworkLocationRequest::Run() : HttpPost request was cancelled.\n"));
    return;
  }
  if (listener_) {
    Position position;
    std::string response_body;
    if (result) {
      // If HttpPost succeeded, payload_data is guaranteed to be non-NULL.
      assert(payload_data.get());
      if (!payload_data->Length() ||
          !BlobToString(payload_data.get(), &response_body)) {
        LOG(("NetworkLocationRequest::Run() : Failed to get response body.\n"));
      }
    }

解析出位置信息

Java代码

1. std::string16access_token;
2. GetLocationFromResponse(result,payload.status_code,response_body,
3. timestamp_,url_,is_reverse_geocode_,
4. &position,&access_token);

std::string16 access_token;
    GetLocationFromResponse(result, payload.status_code, response_body,
                            timestamp_, url_, is_reverse_geocode_,
                            &position, &access_token);

通知位置信息的监听者。

Java代码

1. boolserver_error=
2. !result||(payload.status_code>=500&&payload.status_code<600);
3. listener_->LocationResponseAvailable(position,server_error,access_token);
4. }
5. }

 bool server_error =
        !result || (payload.status_code >= 500 && payload.status_code < 600);
    listener_->LocationResponseAvailable(position, server_error, access_token);
  }
}

有人会问，请求是发哪个服务器的？当然是google了，缺省的URL是：

Java代码

1. staticconstchar16*kDefaultLocationProviderUrl=
2. STRING16(L"https://www.google.com/loc/json");

static const char16 *kDefaultLocationProviderUrl =
    STRING16(L"https://www.google.com/loc/json");

回过头来，我们再总结一下：

1.WIFI和基站定位过程如下：


2.NetworkLocationProvider和 NetworkLocationRequest各有一个线程来异步处理请求。

3.这里的NetworkLocationProvider与android中的 NetworkLocationProvider并不是同一个东西，这里是给gears用的，要在android的google map中使用，还得包装成android中的NetworkLocationProvider的接口。

4.WIFI和基站定位与平台无关，只要你能拿到WIFI扫描结果或基站信息，而且能访问google的定位服务器，不管你是Android平台，Windows Mobile平台还是传统的feature phone，你都可以实现WIFI和基站定位。


附: WIFI和基站定位原理

无论是WIFI的接入点，还是移动网络的基站设备，它们的位置基本上都是固定的。设备端(如手机）可以找到它们的ID，现在的问题就是如何通过这些ID找到对应的位置。网上的流行的说法是开车把所有每个位置都跑一遍，把这些设备的位置与 GPS测试的位置关联起来。


参考资料：
Gears:[url] http://gears.googlecode.com/[/url]
Google 地图 API:[url] http://code.google.com/intl/zh-CN/apis/maps/documentation/reference.html[/url]
wifi定位技术:[url] http://blog.youkuaiyun.com/NewMap/archive/2009/03/17/3999337.aspx
[/url]

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