1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
|
/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.server.wifi.util;
import android.annotation.NonNull;
import android.os.Handler;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;
import com.android.internal.util.Preconditions;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* Holds a list of external app-provided binder callback objects and tracks the death
* of the callback object.
* @param <T> Callback object type.
*/
public class ExternalCallbackTracker<T> {
private static final String TAG = "WifiExternalCallbackTracker";
/* Limit on number of registered callbacks to track and prevent potential memory leak */
private static final int NUM_CALLBACKS_WARN_LIMIT = 10;
private static final int NUM_CALLBACKS_WTF_LIMIT = 20;
/**
* Container for storing info about each external callback and tracks it's death.
*/
private static class ExternalCallbackHolder<T> implements IBinder.DeathRecipient {
private final IBinder mBinder;
private final T mCallbackObject;
private final DeathCallback mDeathCallback;
/**
* Callback to be invoked on death of the app hosting the binder.
*/
public interface DeathCallback {
/**
* Called when the corresponding app has died.
*/
void onDeath();
}
private ExternalCallbackHolder(@NonNull IBinder binder, @NonNull T callbackObject,
@NonNull DeathCallback deathCallback) {
mBinder = Preconditions.checkNotNull(binder);
mCallbackObject = Preconditions.checkNotNull(callbackObject);
mDeathCallback = Preconditions.checkNotNull(deathCallback);
}
/**
* Static method to create a new {@link ExternalCallbackHolder} object and register for
* death notification of the associated binder.
* @return an instance of {@link ExternalCallbackHolder} if there are no failures, otherwise
* null.
*/
public static <T> ExternalCallbackHolder createAndLinkToDeath(
@NonNull IBinder binder, @NonNull T callbackObject,
@NonNull DeathCallback deathCallback) {
ExternalCallbackHolder<T> externalCallback =
new ExternalCallbackHolder<T>(binder, callbackObject, deathCallback);
try {
binder.linkToDeath(externalCallback, 0);
} catch (RemoteException e) {
Log.e(TAG, "Error on linkToDeath - " + e);
return null;
}
return externalCallback;
}
/**
* Unlinks this object from binder death.
*/
public void reset() {
mBinder.unlinkToDeath(this, 0);
}
/**
* Retrieve the callback object.
*/
public T getCallback() {
return mCallbackObject;
}
/**
* App hosting the binder has died.
*/
@Override
public void binderDied() {
mDeathCallback.onDeath();
Log.d(TAG, "Binder died " + mBinder);
}
}
private final Map<Integer, ExternalCallbackHolder<T>> mCallbacks;
private final Handler mHandler;
public ExternalCallbackTracker(Handler handler) {
mHandler = handler;
mCallbacks = new HashMap<>();
}
/**
* Add a callback object to tracker.
* @return true on success, false on failure.
*/
public boolean add(@NonNull IBinder binder, @NonNull T callbackObject, int callbackIdentifier) {
ExternalCallbackHolder<T> externalCallback = ExternalCallbackHolder.createAndLinkToDeath(
binder, callbackObject, () -> {
mHandler.post(() -> {
Log.d(TAG, "Remove external callback on death " + callbackIdentifier);
remove(callbackIdentifier);
});
});
if (externalCallback == null) return false;
if (mCallbacks.containsKey(callbackIdentifier) && remove(callbackIdentifier)) {
Log.d(TAG, "Replacing callback " + callbackIdentifier);
}
mCallbacks.put(callbackIdentifier, externalCallback);
if (mCallbacks.size() > NUM_CALLBACKS_WTF_LIMIT) {
Log.wtf(TAG, "Too many callbacks: " + mCallbacks.size());
} else if (mCallbacks.size() > NUM_CALLBACKS_WARN_LIMIT) {
Log.w(TAG, "Too many callbacks: " + mCallbacks.size());
}
return true;
}
/**
* Remove a callback object to tracker.
* @return true on success, false on failure.
*/
public boolean remove(int callbackIdentifier) {
ExternalCallbackHolder<T> externalCallback = mCallbacks.remove(callbackIdentifier);
if (externalCallback == null) {
Log.w(TAG, "Unknown external callback " + callbackIdentifier);
return false;
}
externalCallback.reset();
return true;
}
/**
* Retrieve all the callback objects in the tracker.
*/
public List<T> getCallbacks() {
List<T> callbacks = new ArrayList<>();
for (ExternalCallbackHolder<T> externalCallback : mCallbacks.values()) {
callbacks.add(externalCallback.getCallback());
}
return callbacks;
}
/**
* Retrieve the number of callback objects in the tracker.
*/
public int getNumCallbacks() {
return mCallbacks.size();
}
/**
* Remove all callbacks registered.
*/
public void clear() {
for (ExternalCallbackHolder<T> externalCallback : mCallbacks.values()) {
externalCallback.reset();
}
mCallbacks.clear();
}
}
|
