| /* |
| * 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.annotation.Nullable; |
| 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<T> createAndLinkToDeath( |
| @NonNull IBinder binder, @NonNull T callbackObject, |
| @NonNull DeathCallback deathCallback) { |
| ExternalCallbackHolder<T> externalCallback = |
| new ExternalCallbackHolder<>(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)) { |
| Log.d(TAG, "Replacing callback " + callbackIdentifier); |
| remove(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 Removed object instance on success, null on failure. |
| */ |
| public @Nullable T remove(int callbackIdentifier) { |
| ExternalCallbackHolder<T> externalCallback = mCallbacks.remove(callbackIdentifier); |
| if (externalCallback == null) { |
| Log.w(TAG, "Unknown external callback " + callbackIdentifier); |
| return null; |
| } |
| externalCallback.reset(); |
| return externalCallback.getCallback(); |
| } |
| |
| /** |
| * 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(); |
| } |
| } |