1 /* 2 * Copyright (C) 2013 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.documentsui; 18 19 import android.os.AsyncTask; 20 21 import androidx.annotation.GuardedBy; 22 23 import java.lang.ref.WeakReference; 24 import java.util.ArrayList; 25 import java.util.HashMap; 26 import java.util.concurrent.Executor; 27 import java.util.concurrent.LinkedBlockingQueue; 28 29 public class ProviderExecutor extends Thread implements Executor { 30 31 @GuardedBy("sExecutors") 32 private static HashMap<String, ProviderExecutor> sExecutors = new HashMap<>(); 33 forAuthority(String authority)34 public static ProviderExecutor forAuthority(String authority) { 35 synchronized (sExecutors) { 36 ProviderExecutor executor = sExecutors.get(authority); 37 if (executor == null) { 38 executor = new ProviderExecutor(); 39 executor.setName("ProviderExecutor: " + authority); 40 executor.start(); 41 sExecutors.put(authority, executor); 42 } 43 return executor; 44 } 45 } 46 47 public interface Preemptable { preempt()48 void preempt(); 49 } 50 51 private final LinkedBlockingQueue<Runnable> mQueue = new LinkedBlockingQueue<Runnable>(); 52 53 private final ArrayList<WeakReference<Preemptable>> mPreemptable = new ArrayList<>(); 54 preempt()55 private void preempt() { 56 synchronized (mPreemptable) { 57 int count = 0; 58 for (WeakReference<Preemptable> ref : mPreemptable) { 59 final Preemptable p = ref.get(); 60 if (p != null) { 61 count++; 62 p.preempt(); 63 } 64 } 65 mPreemptable.clear(); 66 } 67 } 68 69 /** 70 * Execute the given task. If given task is not {@link Preemptable}, it will 71 * preempt all outstanding preemptable tasks. 72 */ execute(AsyncTask<P, ?, ?> task, P... params)73 public <P> void execute(AsyncTask<P, ?, ?> task, P... params) { 74 if (task instanceof Preemptable) { 75 synchronized (mPreemptable) { 76 mPreemptable.add(new WeakReference<Preemptable>((Preemptable) task)); 77 } 78 task.executeOnExecutor(mNonPreemptingExecutor, params); 79 } else { 80 task.executeOnExecutor(this, params); 81 } 82 } 83 84 private Executor mNonPreemptingExecutor = new Executor() { 85 @Override 86 public void execute(Runnable command) { 87 assert(command != null); 88 mQueue.add(command); 89 } 90 }; 91 92 @Override execute(Runnable command)93 public void execute(Runnable command) { 94 preempt(); 95 assert(command != null); 96 mQueue.add(command); 97 } 98 99 @Override run()100 public void run() { 101 while (true) { 102 try { 103 final Runnable command = mQueue.take(); 104 command.run(); 105 } catch (InterruptedException e) { 106 // That was weird; let's go look for more tasks. 107 } 108 } 109 } 110 } 111