| /* |
| * Copyright (C) 2016 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.printservice.recommendation.util; |
| |
| import android.net.nsd.NsdManager; |
| import android.net.nsd.NsdServiceInfo; |
| |
| import androidx.annotation.GuardedBy; |
| import androidx.annotation.NonNull; |
| |
| import java.util.LinkedList; |
| |
| /** |
| * Nsd resolve requests for the same info cancel each other. Hence this class synchronizes the |
| * resolutions to hide this effect. |
| */ |
| public class NsdResolveQueue { |
| /** Lock for {@link #sInstance} */ |
| private static final Object sLock = new Object(); |
| |
| /** Instance of this singleton */ |
| @GuardedBy("sLock") |
| private static NsdResolveQueue sInstance; |
| |
| /** Lock for {@link #mResolveRequests} */ |
| private final Object mLock = new Object(); |
| |
| /** Current set of registered service info resolve attempts */ |
| @GuardedBy("mLock") |
| private final LinkedList<NsdResolveRequest> mResolveRequests = new LinkedList<>(); |
| |
| public static NsdResolveQueue getInstance() { |
| synchronized (sLock) { |
| if (sInstance == null) { |
| sInstance = new NsdResolveQueue(); |
| } |
| |
| return sInstance; |
| } |
| } |
| |
| /** |
| * Container for a request to resolve a serviceInfo. |
| */ |
| private static class NsdResolveRequest { |
| final @NonNull NsdManager nsdManager; |
| final @NonNull NsdServiceInfo serviceInfo; |
| final @NonNull NsdManager.ResolveListener listener; |
| |
| private NsdResolveRequest(@NonNull NsdManager nsdManager, |
| @NonNull NsdServiceInfo serviceInfo, @NonNull NsdManager.ResolveListener listener) { |
| this.nsdManager = nsdManager; |
| this.serviceInfo = serviceInfo; |
| this.listener = listener; |
| } |
| } |
| |
| /** |
| * Resolve a serviceInfo or queue the request if there is a request currently in flight. |
| * |
| * @param nsdManager The nsd manager to use |
| * @param serviceInfo The service info to resolve |
| * @param listener The listener to call back once the info is resolved. |
| */ |
| public void resolve(@NonNull NsdManager nsdManager, @NonNull NsdServiceInfo serviceInfo, |
| @NonNull NsdManager.ResolveListener listener) { |
| synchronized (mLock) { |
| mResolveRequests.addLast(new NsdResolveRequest(nsdManager, serviceInfo, |
| new ListenerWrapper(listener))); |
| |
| if (mResolveRequests.size() == 1) { |
| resolveNextRequest(); |
| } |
| } |
| } |
| |
| /** |
| * Wrapper for a {@link NsdManager.ResolveListener}. Calls the listener and then |
| * {@link #resolveNextRequest()}. |
| */ |
| private class ListenerWrapper implements NsdManager.ResolveListener { |
| private final @NonNull NsdManager.ResolveListener mListener; |
| |
| private ListenerWrapper(@NonNull NsdManager.ResolveListener listener) { |
| mListener = listener; |
| } |
| |
| @Override |
| public void onResolveFailed(NsdServiceInfo serviceInfo, int errorCode) { |
| mListener.onResolveFailed(serviceInfo, errorCode); |
| |
| synchronized (mLock) { |
| mResolveRequests.pop(); |
| resolveNextRequest(); |
| } |
| } |
| |
| @Override |
| public void onServiceResolved(NsdServiceInfo serviceInfo) { |
| mListener.onServiceResolved(serviceInfo); |
| |
| synchronized (mLock) { |
| mResolveRequests.pop(); |
| resolveNextRequest(); |
| } |
| } |
| } |
| |
| /** |
| * Resolve the next request if there is one. |
| */ |
| private void resolveNextRequest() { |
| if (!mResolveRequests.isEmpty()) { |
| NsdResolveRequest request = mResolveRequests.getFirst(); |
| |
| request.nsdManager.resolveService(request.serviceInfo, request.listener); |
| } |
| } |
| |
| } |