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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.bips.discovery;
     18 
     19 import android.content.Context;
     20 import android.net.nsd.NsdManager;
     21 import android.net.nsd.NsdServiceInfo;
     22 import android.os.Handler;
     23 import android.util.Log;
     24 
     25 import java.util.LinkedList;
     26 
     27 /**
     28  * Queues Nsd resolve requests to prevent multiple simultaneous requests to NsdManager
     29  */
     30 public class NsdResolveQueue {
     31     private static final String TAG = NsdResolveQueue.class.getSimpleName();
     32     private static final boolean DEBUG = false;
     33 
     34     private final NsdManager mNsdManager;
     35     private final Handler mMainHandler;
     36 
     37     /** Current set of registered service info resolve attempts */
     38     private LinkedList<NsdResolveRequest> mResolveRequests = new LinkedList<>();
     39 
     40     public NsdResolveQueue(Context context, NsdManager nsdManager) {
     41         mNsdManager = nsdManager;
     42         mMainHandler = new Handler(context.getMainLooper());
     43     }
     44 
     45     /** Return the {@link NsdManager} used by this queue */
     46     NsdManager getNsdManager() {
     47         return mNsdManager;
     48     }
     49 
     50     /**
     51      * Resolve a serviceInfo or queue the request if there is a request currently in flight.
     52      *
     53      * @param serviceInfo The service info to resolve
     54      * @param listener    The listener to call back once the info is resolved.
     55      */
     56     public NsdResolveRequest resolve(NsdServiceInfo serviceInfo,
     57             NsdManager.ResolveListener listener) {
     58         if (DEBUG) {
     59             Log.d(TAG, "Adding resolve of " + serviceInfo.getServiceName() + " to queue size="
     60                     + mResolveRequests.size());
     61         }
     62         NsdResolveRequest request = new NsdResolveRequest(mNsdManager, serviceInfo, listener);
     63         mResolveRequests.addLast(request);
     64         if (mResolveRequests.size() == 1) {
     65             resolveNextRequest();
     66         }
     67         return request;
     68     }
     69 
     70     /**
     71      * Resolve the next request if there is one.
     72      */
     73     private void resolveNextRequest() {
     74         if (!mResolveRequests.isEmpty()) {
     75             mResolveRequests.getFirst().start();
     76         }
     77     }
     78 
     79     /**
     80      * Holds a request to resolve a {@link NsdServiceInfo}
     81      */
     82     class NsdResolveRequest implements NsdManager.ResolveListener {
     83         private final NsdManager mNsdManager;
     84         private final NsdServiceInfo mServiceInfo;
     85         private final NsdManager.ResolveListener mListener;
     86         private long mStartTime;
     87 
     88         private NsdResolveRequest(NsdManager nsdManager,
     89                 NsdServiceInfo serviceInfo,
     90                 NsdManager.ResolveListener listener) {
     91             mNsdManager = nsdManager;
     92             mServiceInfo = serviceInfo;
     93             mListener = listener;
     94         }
     95 
     96         private void start() {
     97             mStartTime = System.currentTimeMillis();
     98             if (DEBUG) Log.d(TAG, "resolveService " + mServiceInfo.getServiceName());
     99             mNsdManager.resolveService(mServiceInfo, this);
    100         }
    101 
    102         void cancel() {
    103             // Note: resolve requests can only be cancelled if they have not yet begun
    104             if (!mResolveRequests.isEmpty() && mResolveRequests.get(0) != this) {
    105                 mResolveRequests.remove(this);
    106             }
    107         }
    108 
    109         @Override
    110         public void onResolveFailed(NsdServiceInfo serviceInfo, int errorCode) {
    111             if (DEBUG) {
    112                 Log.d(TAG, "onResolveFailed " + serviceInfo.getServiceName() + " errorCode="
    113                         + errorCode + " (" + (System.currentTimeMillis() - mStartTime) + " ms)");
    114             }
    115             mMainHandler.post(() -> {
    116                 mListener.onResolveFailed(serviceInfo, errorCode);
    117                 mResolveRequests.pop();
    118                 resolveNextRequest();
    119             });
    120         }
    121 
    122         @Override
    123         public void onServiceResolved(NsdServiceInfo serviceInfo) {
    124             if (DEBUG) {
    125                 Log.d(TAG, "onServiceResolved " + serviceInfo.getServiceName()
    126                         + " (" + (System.currentTimeMillis() - mStartTime) + " ms)");
    127             }
    128             mMainHandler.post(() -> {
    129                 mListener.onServiceResolved(serviceInfo);
    130                 mResolveRequests.pop();
    131                 resolveNextRequest();
    132             });
    133         }
    134     }
    135 }
    136