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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.server.wifi;
     18 
     19 import android.os.IBinder;
     20 import android.os.IBinder.DeathRecipient;
     21 import android.os.RemoteException;
     22 import com.android.internal.util.StateMachine;
     23 
     24 /**
     25  * Allows StateMachine instances to subscribe to binder death.
     26  *
     27  * @hide
     28  */
     29 public class StateMachineDeathRecipient implements DeathRecipient {
     30 
     31     private final StateMachine mStateMachine;
     32     private final int mDeathCommand;
     33     private IBinder mLinkedBinder;
     34 
     35     /**
     36      * Construct a StateMachineDeathRecipient.
     37      *
     38      * @param sm StateMachine instance to receive a message upon Binder death.
     39      * @param command message to send the state machine.
     40      */
     41     public StateMachineDeathRecipient(StateMachine sm, int command) {
     42         mStateMachine = sm;
     43         mDeathCommand = command;
     44     }
     45 
     46     /**
     47      * Listen for the death of a binder.
     48      *
     49      * This method will unlink from death notifications from any
     50      * previously linked IBinder instance.
     51      *
     52      * @param binder remote object to listen for death.
     53      * @return true iff we have successfully subscribed to death notifications of a live
     54      *         IBinder instance.
     55      */
     56     public boolean linkToDeath(IBinder binder) {
     57         unlinkToDeath();
     58         try {
     59             binder.linkToDeath(this, 0);
     60         } catch (RemoteException e) {
     61             // The remote has already died.
     62             return false;
     63         }
     64         mLinkedBinder = binder;
     65         return true;
     66     }
     67 
     68     /**
     69      * Unlink from notifications from the last linked IBinder instance.
     70      */
     71     public void unlinkToDeath() {
     72         if (mLinkedBinder == null) {
     73             return;
     74         }
     75         mLinkedBinder.unlinkToDeath(this, 0);
     76         mLinkedBinder = null;
     77     }
     78 
     79     /**
     80      * Called by the binder subsystem upon remote object death.
     81      */
     82     @Override
     83     public void binderDied() {
     84         mStateMachine.sendMessage(mDeathCommand);
     85     }
     86 }