Refactor and reorganize listener multiplexers (490c46ca) · Commits · e / os / android_frameworks_base

core/java/com/android/internal/listeners/ListenerTransport.java

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		/*
		* Copyright (C) 2020 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.internal.listeners;


		import android.annotation.NonNull;
		import android.annotation.Nullable;

		import com.android.internal.util.Preconditions;

		import java.util.Objects;
		import java.util.concurrent.Executor;
		import java.util.concurrent.RejectedExecutionException;
		import java.util.function.Consumer;

		/**
		* A listener registration object which holds data associated with a listener, such the executor
		* the listener should run on.
		*
		* @param <TListener> listener type
		*/
		public class ListenerTransport<TListener> {

		private final Executor mExecutor;

		private volatile @Nullable TListener mListener;

		protected ListenerTransport(@NonNull Executor executor, @NonNull TListener listener) {
		Preconditions.checkArgument(executor != null, "invalid null executor");
		Preconditions.checkArgument(listener != null, "invalid null listener/callback");
		mExecutor = executor;
		mListener = listener;
		}

		final boolean isRegistered() {
		return mListener != null;
		}

		/**
		* Prevents any listener invocations that happen-after this call.
		*/
		public final void unregister() {
		mListener = null;
		}

		/**
		* Executes the given operation for the listener. {@link #onOperationFinished(Consumer)} will
		* always be invoked at some time after this method, regardless of if the listener invocation
		* happens or if the operation fails in some way.
		*/
		public final void execute(@NonNull Consumer<TListener> operation) {
		Objects.requireNonNull(operation);
		try {
		mExecutor.execute(() -> {
		try {
		TListener listener = mListener;
		if (listener == null) {
		return;
		}

		operation.accept(listener);
		} finally {
		onOperationFinished(operation);
		}
		});
		} catch (RejectedExecutionException e) {
		onOperationFinished(operation);
		}
		}

		/**
		* Invoked when an operation is finished. This method will always be called once for every call
		* to {@link #execute(Consumer)}, regardless of whether the operation encountered any
		* error or failed to execute in any way. May run on any thread.
		*/
		protected void onOperationFinished(@NonNull Consumer<TListener> operation) {}

		@Override
		public final boolean equals(Object obj) {
		// intentionally bound to reference equality so removal works as expected
		return this == obj;
		}

		@Override
		public final int hashCode() {
		return super.hashCode();
		}
		}

core/java/com/android/internal/listeners/ListenerTransportManager.java

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		/*
		* Copyright (C) 2020 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.internal.listeners;

		import android.annotation.NonNull;
		import android.os.RemoteException;
		import android.util.ArrayMap;

		import com.android.internal.annotations.GuardedBy;
		import com.android.internal.util.Preconditions;

		import java.util.Objects;

		/**
		* A listener manager which tracks listeners along with their keys. This class enforces proper use
		* of transport objects and ensure unregistration race conditions are handled properly. If listeners
		* should be multiplexed before being sent to the server, see {@link ListenerTransportMultiplexer}
		* instead.
		*
		* @param <TTransport> transport type
		*/
		public abstract class ListenerTransportManager<TTransport extends ListenerTransport<?>> {

		@GuardedBy("mTransports")
		private final ArrayMap<Object, TTransport> mTransports = new ArrayMap<>();

		/**
		* Should be implemented to register the transport with the server.
		*
		* @see #reregisterWithServer(ListenerTransport, ListenerTransport)
		*/
		protected abstract void registerWithServer(TTransport transport) throws RemoteException;

		/**
		* Invoked when the server already has a transport registered for a key, and it is being
		* replaced with a new transport. The default implementation unregisters the old transport, then
		* registers the new transport, but this may be overridden by subclasses in order to reregister
		* more efficiently.
		*/
		protected void reregisterWithServer(TTransport oldTransport, TTransport newTransport)
		throws RemoteException {
		unregisterWithServer(oldTransport);
		registerWithServer(newTransport);
		}

		/**
		* Should be implemented to unregister the transport from the server.
		*/
		protected abstract void unregisterWithServer(TTransport transport) throws RemoteException;

		/**
		* Adds a new transport with the given key and makes a call to add the transport server side. If
		* a transport already exists with that key, it will be replaced by the new transport and
		* {@link #reregisterWithServer(ListenerTransport, ListenerTransport)} will be invoked to
		* replace the old transport with the new transport server side. If no transport exists with
		* that key, it will be added server side via {@link #registerWithServer(ListenerTransport)}.
		*/
		public void registerListener(@NonNull Object key, @NonNull TTransport transport) {
		Objects.requireNonNull(key);
		Objects.requireNonNull(transport);

		synchronized (mTransports) {
		TTransport oldTransport = mTransports.put(key, transport);
		if (oldTransport != null) {
		oldTransport.unregister();
		}

		Preconditions.checkState(transport.isRegistered());

		boolean registered = false;
		try {
		if (oldTransport == null) {
		registerWithServer(transport);
		} else {
		reregisterWithServer(oldTransport, transport);
		}
		registered = true;
		} catch (RemoteException e) {
		throw e.rethrowFromSystemServer();
		} finally {
		if (!registered) {
		transport.unregister();
		mTransports.remove(key);
		}
		}
		}
		}

		/**
		* Removes the transport with the given key, and makes a call to remove the transport server
		* side via {@link #unregisterWithServer(ListenerTransport)}.
		*/
		public void unregisterListener(@NonNull Object key) {
		Objects.requireNonNull(key);

		synchronized (mTransports) {
		TTransport transport = mTransports.remove(key);
		if (transport == null) {
		return;
		}

		transport.unregister();
		try {
		unregisterWithServer(transport);
		} catch (RemoteException e) {
		throw e.rethrowFromSystemServer();
		}
		}
		}

		/**
		* Removes the given transport with the given key if such a mapping exists. This only removes
		* the client registration, it does not make any calls to remove the transport server side. The
		* intended use is for when the transport is already removed server side and only client side
		* cleanup is necessary.
		*/
		public void removeTransport(@NonNull Object key, @NonNull ListenerTransport<?> transport) {
		Objects.requireNonNull(key);
		Objects.requireNonNull(transport);

		synchronized (mTransports) {
		TTransport typedTransport = mTransports.get(key);
		if (typedTransport != transport) {
		return;
		}

		mTransports.remove(key);
		typedTransport.unregister();
		}
		}
		}

core/java/com/android/internal/listeners/ListenerTransportMultiplexer.java

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		/*
		* Copyright (C) 2020 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.internal.listeners;

		import android.annotation.NonNull;
		import android.annotation.Nullable;
		import android.os.Build;
		import android.os.RemoteException;
		import android.util.ArrayMap;

		import com.android.internal.annotations.GuardedBy;
		import com.android.internal.util.IndentingPrintWriter;
		import com.android.internal.util.Preconditions;

		import java.io.FileDescriptor;
		import java.io.PrintWriter;
		import java.util.ArrayList;
		import java.util.Collection;
		import java.util.Objects;
		import java.util.concurrent.Executor;
		import java.util.function.Consumer;

		/**
		* A listener multiplexer designed for use by client-side code. This class ensures that listeners
		* are never invoked while a lock is held. This class is only useful for multiplexing listeners -
		* if all client listeners can be combined into a single server request, and all server results will
		* be delivered to all clients. If this is not the case, see {@link ListenerTransportManager}
		* instead.
		*
		* By default, the multiplexer will replace requests on the server simply by registering the new
		* request and trusting the server to know this is replacing the old request. If the server needs to
		* have the old request unregistered first, subclasses should override
		* {@link #reregisterWithServer(Object, Object)}.
		*
		* @param <TRequest> listener request type, may be Void
		* @param <TListener> listener type
		*/
		public abstract class ListenerTransportMultiplexer<TRequest, TListener> {

		private final Object mLock = new Object();

		@GuardedBy("mLock")
		private ArrayMap<Object, RequestListenerTransport<TRequest, TListener>> mRegistrations =
		new ArrayMap<>();

		@GuardedBy("mLock")
		private boolean mServiceRegistered = false;

		@GuardedBy("mLock")
		private TRequest mCurrentRequest;

		/**
		* Should be implemented to register the given merged request with the server.
		*
		* @see #reregisterWithServer(Object, Object)
		*/
		protected abstract void registerWithServer(TRequest mergedRequest) throws RemoteException;

		/**
		* Invoked when the server already has a request registered, and it is being replaced with a new
		* request. The default implementation unregisters first, then registers the new request, but
		* this may be overridden by subclasses in order to reregister more efficiently.
		*/
		protected void reregisterWithServer(TRequest oldMergedRequest, TRequest mergedRequest)
		throws RemoteException {
		registerWithServer(mergedRequest);
		}

		/**
		* Should be implemented to unregister from the server.
		*/
		protected abstract void unregisterWithServer() throws RemoteException;

		/**
		* Called in order to generate a merged request from the given requests. The list of requests
		* will never be empty.
		*/
		protected @Nullable TRequest mergeRequests(Collection<TRequest> requests) {
		if (Build.IS_DEBUGGABLE) {
		for (TRequest request : requests) {
		// if using non-null requests then implementations must override this method
		Preconditions.checkState(request == null);
		}
		}

		return null;
		}

		/**
		* Adds a new listener with no request, using the listener as the key.
		*/
		public void addListener(@NonNull TListener listener, @NonNull Executor executor) {
		addListener(listener, null, listener, executor);
		}

		/**
		* Adds a new listener with the given request, using the listener as the key.
		*/
		public void addListener(@Nullable TRequest request, @NonNull TListener listener,
		@NonNull Executor executor) {
		addListener(listener, request, listener, executor);
		}

		/**
		* Adds a new listener with the given request using a custom key.
		*/
		public void addListener(@NonNull Object key, @Nullable TRequest request,
		@NonNull TListener listener, @NonNull Executor executor) {
		Objects.requireNonNull(key);
		RequestListenerTransport<TRequest, TListener> registration =
		new RequestListenerTransport<>(request, executor, listener);

		synchronized (mLock) {
		ArrayMap<Object, RequestListenerTransport<TRequest, TListener>> newRegistrations =
		new ArrayMap<>(mRegistrations.size() + 1);
		newRegistrations.putAll(mRegistrations);
		RequestListenerTransport<TRequest, TListener> old = newRegistrations.put(key,
		registration);
		mRegistrations = newRegistrations;

		if (old != null) {
		old.unregister();
		}

		updateService();
		}
		}

		/**
		* Removes the listener with the given key.
		*/
		public void removeListener(@NonNull Object key) {
		Objects.requireNonNull(key);

		synchronized (mLock) {
		if (!mRegistrations.containsKey(key)) {
		return;
		}

		ArrayMap<Object, RequestListenerTransport<TRequest, TListener>> newRegistrations =
		new ArrayMap<>(mRegistrations);
		RequestListenerTransport<TRequest, TListener> old = newRegistrations.remove(key);
		mRegistrations = newRegistrations;

		if (old != null) {
		old.unregister();
		updateService();
		}
		}
		}

		private void updateService() {
		synchronized (mLock) {
		if (mRegistrations.isEmpty()) {
		mCurrentRequest = null;
		if (mServiceRegistered) {
		try {
		mServiceRegistered = false;
		unregisterWithServer();
		} catch (RemoteException e) {
		throw e.rethrowFromSystemServer();
		}
		}
		return;
		}

		ArrayList<TRequest> requests = new ArrayList<>(mRegistrations.size());
		for (int i = 0; i < mRegistrations.size(); i++) {
		requests.add(mRegistrations.valueAt(i).getRequest());
		}

		TRequest merged = mergeRequests(requests);
		if (!mServiceRegistered \|\| !Objects.equals(merged, mCurrentRequest)) {
		TRequest old = mCurrentRequest;
		mCurrentRequest = null;
		try {
		if (mServiceRegistered) {
		// if a remote exception is thrown the service should not be registered
		mServiceRegistered = false;
		reregisterWithServer(old, merged);
		} else {
		registerWithServer(merged);
		}
		mCurrentRequest = merged;
		mServiceRegistered = true;
		} catch (RemoteException e) {
		throw e.rethrowFromSystemServer();
		}
		}
		}
		}

		protected final void deliverToListeners(Consumer<TListener> operation) {
		ArrayMap<Object, RequestListenerTransport<TRequest, TListener>> registrations;
		synchronized (mLock) {
		registrations = mRegistrations;
		}

		try {
		for (int i = 0; i < registrations.size(); i++) {
		registrations.valueAt(i).execute(operation);
		}
		} finally {
		onOperationFinished(operation);
		}
		}

		/**
		* Invoked when an operation is finished. This method will always be called once for every call
		* to {@link #deliverToListeners(Consumer)}, regardless of whether the operation encountered any
		* error or failed to execute in any way for any listeners.
		*/
		protected void onOperationFinished(@NonNull Consumer<TListener> operation) {}

		/**
		* Dumps debug information.
		*/
		public void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
		IndentingPrintWriter ipw = new IndentingPrintWriter(pw, " ");

		ArrayMap<Object, RequestListenerTransport<TRequest, TListener>> registrations;
		synchronized (mLock) {
		registrations = mRegistrations;

		ipw.print("service: ");
		if (mServiceRegistered) {
		if (mCurrentRequest == null) {
		pw.print("request registered");
		} else {
		pw.print("request registered - " + mCurrentRequest);
		}
		} else {
		pw.print("unregistered");
		}
		ipw.println();
		}

		if (!registrations.isEmpty()) {
		ipw.println("listeners:");

		ipw.increaseIndent();
		for (int i = 0; i < registrations.size(); i++) {
		ipw.print(registrations.valueAt(i));
		}
		ipw.decreaseIndent();
		}
		}
		}

location/java/android/location/util/listeners/ClientListenerManager.java→core/java/com/android/internal/listeners/RequestListenerTransport.java

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		@@ -14,56 +14,32 @@
		* limitations under the License.
		*/

		package android.location.util.listeners;
		package com.android.internal.listeners;

		import android.annotation.NonNull;
		import android.annotation.Nullable;
		import android.location.util.listeners.AbstractListenerManager.Registration;

		import java.util.concurrent.Executor;

		/**
		* A listener manager for client side implementations, where there is no need to deal with any
		* complications other than muxing listeners. Listeners without associated requests are supported
		* without any further work, and listeners with requests must produce muxed requests of the same
		* type.
		* A listener transport with an associated request.
		*
		* @param <TRequest> request type
		* @param <TListener> listener type
		* @hide
		*/
		public abstract class ClientListenerManager<TRequest, TListener> extends
		AbstractListenerManager<Object, TRequest, TListener, Registration<TRequest, TListener>,
		TRequest> {
		public class RequestListenerTransport<TRequest, TListener> extends ListenerTransport<TListener> {

		/**
		* Adds a new listener with no request.
		*/
		public void addListener(@NonNull TListener listener, @NonNull Executor executor) {
		addListener(listener, null, listener, executor);
		}
		private final @Nullable TRequest mRequest;

		/**
		* Adds a new listener with the given request.
		*/
		public void addListener(@Nullable TRequest request, @NonNull TListener listener,
		@NonNull Executor executor) {
		addListener(listener, request, listener, executor);
		}

		/**
		* Adds a new listener with the given request using a custom key, rather than using the listener
		* as the key.
		*/
		protected void addListener(@NonNull Object key, @Nullable TRequest request,
		@NonNull TListener listener, @NonNull Executor executor) {
		addRegistration(key, new Registration<>(request, executor, listener));
		protected RequestListenerTransport(@Nullable TRequest request, Executor executor,
		TListener listener) {
		super(executor, listener);
		mRequest = request;
		}

		/**
		* Removes the listener with the given key.
		* Returns the request associated with this transport.
		*/
		public void removeListener(@NonNull Object key) {
		removeRegistration(key);
		public final @Nullable TRequest getRequest() {
		return mRequest;
		}
		}

core/tests/coretests/src/com/android/internal/listeners/ListenerTransportMultiplexerTest.java

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+194 −0

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