net/android/network_change_notifier_android.cc

   1 // Copyright (c) 2012 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 ////////////////////////////////////////////////////////////////////////////////
   6 // Threading considerations:
   7 //
   8 // This class is designed to meet various threading guarantees starting from the
   9 // ones imposed by NetworkChangeNotifier:
  10 // - The notifier can be constructed on any thread.
  11 // - GetCurrentConnectionType() can be called on any thread.
  12 //
  13 // The fact that this implementation of NetworkChangeNotifier is backed by a
  14 // Java side singleton class (see NetworkChangeNotifier.java) adds another
  15 // threading constraint:
  16 // - The calls to the Java side (stateful) object must be performed from a
  17 //   single thread. This object happens to be a singleton which is used on the
  18 //   application side on the main thread. Therefore all the method calls from
  19 //   the native NetworkChangeNotifierAndroid class to its Java counterpart are
  20 //   performed on the main thread.
  21 //
  22 // This leads to a design involving the following native classes:
  23 // 1) NetworkChangeNotifierFactoryAndroid ('factory')
  24 // 2) NetworkChangeNotifierDelegateAndroid ('delegate')
  25 // 3) NetworkChangeNotifierAndroid ('notifier')
  26 //
  27 // The factory constructs and owns the delegate. The factory is constructed and
  28 // destroyed on the main thread which makes it construct and destroy the
  29 // delegate on the main thread too. This guarantees that the calls to the Java
  30 // side are performed on the main thread.
  31 // Note that after the factory's construction, the factory's creation method can
  32 // be called from any thread since the delegate's construction (performing the
  33 // JNI calls) already happened on the main thread (when the factory was
  34 // constructed).
  35 //
  36 ////////////////////////////////////////////////////////////////////////////////
  37 // Propagation of network change notifications:
  38 //
  39 // When the factory is requested to create a new instance of the notifier, the
  40 // factory passes the delegate to the notifier (without transferring ownership).
  41 // Note that there is a one-to-one mapping between the factory and the
  42 // delegate as explained above. But the factory naturally creates multiple
  43 // instances of the notifier. That means that there is a one-to-many mapping
  44 // between delegate and notifier (i.e. a single delegate can be shared by
  45 // multiple notifiers).
  46 // At construction the notifier (which is also an observer) subscribes to
  47 // notifications fired by the delegate. These notifications, received by the
  48 // delegate (and forwarded to the notifier(s)), are sent by the Java side
  49 // notifier (see NetworkChangeNotifier.java) and are initiated by the Android
  50 // platform.
  51 // Notifications from the Java side always arrive on the main thread. The
  52 // delegate then forwards these notifications to the threads of each observer
  53 // (network change notifier). The network change notifier than processes the
  54 // state change, and notifies each of its observers on their threads.
  55 //
  56 // This can also be seen as:
  57 // Android platform -> NetworkChangeNotifier (Java) ->
  58 // NetworkChangeNotifierDelegateAndroid -> NetworkChangeNotifierAndroid.
  59
  60 #include "net/android/network_change_notifier_android.h"
  61
  62 namespace net {
  63
  64 NetworkChangeNotifierAndroid::~NetworkChangeNotifierAndroid() {
  65   delegate_->RemoveObserver(this);
  66 }
  67
  68 NetworkChangeNotifier::ConnectionType
  69 NetworkChangeNotifierAndroid::GetCurrentConnectionType() const {
  70   return delegate_->GetCurrentConnectionType();
  71 }
  72
  73 void NetworkChangeNotifierAndroid::OnConnectionTypeChanged() {
  74   NetworkChangeNotifier::NotifyObserversOfIPAddressChange();
  75   NetworkChangeNotifier::NotifyObserversOfConnectionTypeChange();
  76 }
  77
  78 // static
  79 bool NetworkChangeNotifierAndroid::Register(JNIEnv* env) {
  80   return NetworkChangeNotifierDelegateAndroid::Register(env);
  81 }
  82
  83 NetworkChangeNotifierAndroid::NetworkChangeNotifierAndroid(
  84     NetworkChangeNotifierDelegateAndroid* delegate)
  85     : NetworkChangeNotifier(NetworkChangeCalculatorParamsAndroid()),
  86       delegate_(delegate) {
  87   delegate_->AddObserver(this);
  88 }
  89
  90 // static
  91 NetworkChangeNotifier::NetworkChangeCalculatorParams
  92 NetworkChangeNotifierAndroid::NetworkChangeCalculatorParamsAndroid() {
  93   NetworkChangeCalculatorParams params;
  94   // IPAddressChanged is produced immediately prior to ConnectionTypeChanged
  95   // so delay IPAddressChanged so they get merged with the following
  96   // ConnectionTypeChanged signal.
  97   params.ip_address_offline_delay_ = base::TimeDelta::FromSeconds(1);
  98   params.ip_address_online_delay_ = base::TimeDelta::FromSeconds(1);
  99   params.connection_type_offline_delay_ = base::TimeDelta::FromSeconds(0);
 100   params.connection_type_online_delay_ = base::TimeDelta::FromSeconds(0);
 101   return params;
 102 }
 103
 104 }  // namespace net