| /* |
| * Copyright (C) 2008 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 android.os; |
| |
| import android.util.ArrayMap; |
| import android.util.Slog; |
| |
| import java.util.function.Consumer; |
| |
| /** |
| * Takes care of the grunt work of maintaining a list of remote interfaces, |
| * typically for the use of performing callbacks from a |
| * {@link android.app.Service} to its clients. In particular, this: |
| * |
| * <ul> |
| * <li> Keeps track of a set of registered {@link IInterface} callbacks, |
| * taking care to identify them through their underlying unique {@link IBinder} |
| * (by calling {@link IInterface#asBinder IInterface.asBinder()}. |
| * <li> Attaches a {@link IBinder.DeathRecipient IBinder.DeathRecipient} to |
| * each registered interface, so that it can be cleaned out of the list if its |
| * process goes away. |
| * <li> Performs locking of the underlying list of interfaces to deal with |
| * multithreaded incoming calls, and a thread-safe way to iterate over a |
| * snapshot of the list without holding its lock. |
| * </ul> |
| * |
| * <p>To use this class, simply create a single instance along with your |
| * service, and call its {@link #register} and {@link #unregister} methods |
| * as client register and unregister with your service. To call back on to |
| * the registered clients, use {@link #beginBroadcast}, |
| * {@link #getBroadcastItem}, and {@link #finishBroadcast}. |
| * |
| * <p>If a registered callback's process goes away, this class will take |
| * care of automatically removing it from the list. If you want to do |
| * additional work in this situation, you can create a subclass that |
| * implements the {@link #onCallbackDied} method. |
| */ |
| public class RemoteCallbackList<E extends IInterface> { |
| private static final String TAG = "RemoteCallbackList"; |
| |
| /*package*/ ArrayMap<IBinder, Callback> mCallbacks |
| = new ArrayMap<IBinder, Callback>(); |
| private Object[] mActiveBroadcast; |
| private int mBroadcastCount = -1; |
| private boolean mKilled = false; |
| private StringBuilder mRecentCallers; |
| |
| private final class Callback implements IBinder.DeathRecipient { |
| final E mCallback; |
| final Object mCookie; |
| |
| Callback(E callback, Object cookie) { |
| mCallback = callback; |
| mCookie = cookie; |
| } |
| |
| public void binderDied() { |
| synchronized (mCallbacks) { |
| mCallbacks.remove(mCallback.asBinder()); |
| } |
| onCallbackDied(mCallback, mCookie); |
| } |
| } |
| |
| /** |
| * Simple version of {@link RemoteCallbackList#register(E, Object)} |
| * that does not take a cookie object. |
| */ |
| public boolean register(E callback) { |
| return register(callback, null); |
| } |
| |
| /** |
| * Add a new callback to the list. This callback will remain in the list |
| * until a corresponding call to {@link #unregister} or its hosting process |
| * goes away. If the callback was already registered (determined by |
| * checking to see if the {@link IInterface#asBinder callback.asBinder()} |
| * object is already in the list), then it will be left as-is. |
| * Registrations are not counted; a single call to {@link #unregister} |
| * will remove a callback after any number calls to register it. |
| * |
| * @param callback The callback interface to be added to the list. Must |
| * not be null -- passing null here will cause a NullPointerException. |
| * Most services will want to check for null before calling this with |
| * an object given from a client, so that clients can't crash the |
| * service with bad data. |
| * |
| * @param cookie Optional additional data to be associated with this |
| * callback. |
| * |
| * @return Returns true if the callback was successfully added to the list. |
| * Returns false if it was not added, either because {@link #kill} had |
| * previously been called or the callback's process has gone away. |
| * |
| * @see #unregister |
| * @see #kill |
| * @see #onCallbackDied |
| */ |
| public boolean register(E callback, Object cookie) { |
| synchronized (mCallbacks) { |
| if (mKilled) { |
| return false; |
| } |
| // Flag unusual case that could be caused by a leak. b/36778087 |
| logExcessiveCallbacks(); |
| IBinder binder = callback.asBinder(); |
| try { |
| Callback cb = new Callback(callback, cookie); |
| binder.linkToDeath(cb, 0); |
| mCallbacks.put(binder, cb); |
| return true; |
| } catch (RemoteException e) { |
| return false; |
| } |
| } |
| } |
| |
| /** |
| * Remove from the list a callback that was previously added with |
| * {@link #register}. This uses the |
| * {@link IInterface#asBinder callback.asBinder()} object to correctly |
| * find the previous registration. |
| * Registrations are not counted; a single unregister call will remove |
| * a callback after any number calls to {@link #register} for it. |
| * |
| * @param callback The callback to be removed from the list. Passing |
| * null here will cause a NullPointerException, so you will generally want |
| * to check for null before calling. |
| * |
| * @return Returns true if the callback was found and unregistered. Returns |
| * false if the given callback was not found on the list. |
| * |
| * @see #register |
| */ |
| public boolean unregister(E callback) { |
| synchronized (mCallbacks) { |
| Callback cb = mCallbacks.remove(callback.asBinder()); |
| if (cb != null) { |
| cb.mCallback.asBinder().unlinkToDeath(cb, 0); |
| return true; |
| } |
| return false; |
| } |
| } |
| |
| /** |
| * Disable this callback list. All registered callbacks are unregistered, |
| * and the list is disabled so that future calls to {@link #register} will |
| * fail. This should be used when a Service is stopping, to prevent clients |
| * from registering callbacks after it is stopped. |
| * |
| * @see #register |
| */ |
| public void kill() { |
| synchronized (mCallbacks) { |
| for (int cbi=mCallbacks.size()-1; cbi>=0; cbi--) { |
| Callback cb = mCallbacks.valueAt(cbi); |
| cb.mCallback.asBinder().unlinkToDeath(cb, 0); |
| } |
| mCallbacks.clear(); |
| mKilled = true; |
| } |
| } |
| |
| /** |
| * Old version of {@link #onCallbackDied(E, Object)} that |
| * does not provide a cookie. |
| */ |
| public void onCallbackDied(E callback) { |
| } |
| |
| /** |
| * Called when the process hosting a callback in the list has gone away. |
| * The default implementation calls {@link #onCallbackDied(E)} |
| * for backwards compatibility. |
| * |
| * @param callback The callback whose process has died. Note that, since |
| * its process has died, you can not make any calls on to this interface. |
| * You can, however, retrieve its IBinder and compare it with another |
| * IBinder to see if it is the same object. |
| * @param cookie The cookie object original provided to |
| * {@link #register(E, Object)}. |
| * |
| * @see #register |
| */ |
| public void onCallbackDied(E callback, Object cookie) { |
| onCallbackDied(callback); |
| } |
| |
| /** |
| * Prepare to start making calls to the currently registered callbacks. |
| * This creates a copy of the callback list, which you can retrieve items |
| * from using {@link #getBroadcastItem}. Note that only one broadcast can |
| * be active at a time, so you must be sure to always call this from the |
| * same thread (usually by scheduling with {@link Handler}) or |
| * do your own synchronization. You must call {@link #finishBroadcast} |
| * when done. |
| * |
| * <p>A typical loop delivering a broadcast looks like this: |
| * |
| * <pre> |
| * int i = callbacks.beginBroadcast(); |
| * while (i > 0) { |
| * i--; |
| * try { |
| * callbacks.getBroadcastItem(i).somethingHappened(); |
| * } catch (RemoteException e) { |
| * // The RemoteCallbackList will take care of removing |
| * // the dead object for us. |
| * } |
| * } |
| * callbacks.finishBroadcast();</pre> |
| * |
| * @return Returns the number of callbacks in the broadcast, to be used |
| * with {@link #getBroadcastItem} to determine the range of indices you |
| * can supply. |
| * |
| * @see #getBroadcastItem |
| * @see #finishBroadcast |
| */ |
| public int beginBroadcast() { |
| synchronized (mCallbacks) { |
| if (mBroadcastCount > 0) { |
| throw new IllegalStateException( |
| "beginBroadcast() called while already in a broadcast"); |
| } |
| |
| final int N = mBroadcastCount = mCallbacks.size(); |
| if (N <= 0) { |
| return 0; |
| } |
| Object[] active = mActiveBroadcast; |
| if (active == null || active.length < N) { |
| mActiveBroadcast = active = new Object[N]; |
| } |
| for (int i=0; i<N; i++) { |
| active[i] = mCallbacks.valueAt(i); |
| } |
| return N; |
| } |
| } |
| |
| /** |
| * Retrieve an item in the active broadcast that was previously started |
| * with {@link #beginBroadcast}. This can <em>only</em> be called after |
| * the broadcast is started, and its data is no longer valid after |
| * calling {@link #finishBroadcast}. |
| * |
| * <p>Note that it is possible for the process of one of the returned |
| * callbacks to go away before you call it, so you will need to catch |
| * {@link RemoteException} when calling on to the returned object. |
| * The callback list itself, however, will take care of unregistering |
| * these objects once it detects that it is no longer valid, so you can |
| * handle such an exception by simply ignoring it. |
| * |
| * @param index Which of the registered callbacks you would like to |
| * retrieve. Ranges from 0 to 1-{@link #beginBroadcast}. |
| * |
| * @return Returns the callback interface that you can call. This will |
| * always be non-null. |
| * |
| * @see #beginBroadcast |
| */ |
| public E getBroadcastItem(int index) { |
| return ((Callback)mActiveBroadcast[index]).mCallback; |
| } |
| |
| /** |
| * Retrieve the cookie associated with the item |
| * returned by {@link #getBroadcastItem(int)}. |
| * |
| * @see #getBroadcastItem |
| */ |
| public Object getBroadcastCookie(int index) { |
| return ((Callback)mActiveBroadcast[index]).mCookie; |
| } |
| |
| /** |
| * Clean up the state of a broadcast previously initiated by calling |
| * {@link #beginBroadcast}. This must always be called when you are done |
| * with a broadcast. |
| * |
| * @see #beginBroadcast |
| */ |
| public void finishBroadcast() { |
| synchronized (mCallbacks) { |
| if (mBroadcastCount < 0) { |
| throw new IllegalStateException( |
| "finishBroadcast() called outside of a broadcast"); |
| } |
| |
| Object[] active = mActiveBroadcast; |
| if (active != null) { |
| final int N = mBroadcastCount; |
| for (int i=0; i<N; i++) { |
| active[i] = null; |
| } |
| } |
| |
| mBroadcastCount = -1; |
| } |
| } |
| |
| /** |
| * Performs {@code action} on each callback, calling |
| * {@link #beginBroadcast()}/{@link #finishBroadcast()} before/after looping |
| * |
| * @hide |
| */ |
| public void broadcast(Consumer<E> action) { |
| int itemCount = beginBroadcast(); |
| try { |
| for (int i = 0; i < itemCount; i++) { |
| action.accept(getBroadcastItem(i)); |
| } |
| } finally { |
| finishBroadcast(); |
| } |
| } |
| |
| /** |
| * Returns the number of registered callbacks. Note that the number of registered |
| * callbacks may differ from the value returned by {@link #beginBroadcast()} since |
| * the former returns the number of callbacks registered at the time of the call |
| * and the second the number of callback to which the broadcast will be delivered. |
| * <p> |
| * This function is useful to decide whether to schedule a broadcast if this |
| * requires doing some work which otherwise would not be performed. |
| * </p> |
| * |
| * @return The size. |
| */ |
| public int getRegisteredCallbackCount() { |
| synchronized (mCallbacks) { |
| if (mKilled) { |
| return 0; |
| } |
| return mCallbacks.size(); |
| } |
| } |
| |
| /** |
| * Return a currently registered callback. Note that this is |
| * <em>not</em> the same as {@link #getBroadcastItem} and should not be used |
| * interchangeably with it. This method returns the registered callback at the given |
| * index, not the current broadcast state. This means that it is not itself thread-safe: |
| * any call to {@link #register} or {@link #unregister} will change these indices, so you |
| * must do your own thread safety between these to protect from such changes. |
| * |
| * @param index Index of which callback registration to return, from 0 to |
| * {@link #getRegisteredCallbackCount()} - 1. |
| * |
| * @return Returns whatever callback is associated with this index, or null if |
| * {@link #kill()} has been called. |
| */ |
| public E getRegisteredCallbackItem(int index) { |
| synchronized (mCallbacks) { |
| if (mKilled) { |
| return null; |
| } |
| return mCallbacks.valueAt(index).mCallback; |
| } |
| } |
| |
| /** |
| * Return any cookie associated with a currently registered callback. Note that this is |
| * <em>not</em> the same as {@link #getBroadcastCookie} and should not be used |
| * interchangeably with it. This method returns the current cookie registered at the given |
| * index, not the current broadcast state. This means that it is not itself thread-safe: |
| * any call to {@link #register} or {@link #unregister} will change these indices, so you |
| * must do your own thread safety between these to protect from such changes. |
| * |
| * @param index Index of which registration cookie to return, from 0 to |
| * {@link #getRegisteredCallbackCount()} - 1. |
| * |
| * @return Returns whatever cookie object is associated with this index, or null if |
| * {@link #kill()} has been called. |
| */ |
| public Object getRegisteredCallbackCookie(int index) { |
| synchronized (mCallbacks) { |
| if (mKilled) { |
| return null; |
| } |
| return mCallbacks.valueAt(index).mCookie; |
| } |
| } |
| |
| private void logExcessiveCallbacks() { |
| final long size = mCallbacks.size(); |
| final long TOO_MANY = 3000; |
| final long MAX_CHARS = 1000; |
| if (size >= TOO_MANY) { |
| if (size == TOO_MANY && mRecentCallers == null) { |
| mRecentCallers = new StringBuilder(); |
| } |
| if (mRecentCallers != null && mRecentCallers.length() < MAX_CHARS) { |
| mRecentCallers.append(Debug.getCallers(5)); |
| mRecentCallers.append('\n'); |
| if (mRecentCallers.length() >= MAX_CHARS) { |
| Slog.wtf(TAG, "More than " |
| + TOO_MANY + " remote callbacks registered. Recent callers:\n" |
| + mRecentCallers.toString()); |
| mRecentCallers = null; |
| } |
| } |
| } |
| } |
| } |