Home | History | Annotate | Download | only in documentsui 
      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 com.android.internal.annotations.GuardedBy;
     22 import com.android.internal.util.Preconditions;
     23 import com.google.android.collect.Lists;
     24 import com.google.android.collect.Maps;
     25 
     26 import java.lang.ref.WeakReference;
     27 import java.util.ArrayList;
     28 import java.util.HashMap;
     29 import java.util.concurrent.Executor;
     30 import java.util.concurrent.LinkedBlockingQueue;
     31 
     32 public class ProviderExecutor extends Thread implements Executor {
     33 
     34     @GuardedBy("sExecutors")
     35     private static HashMap<String, ProviderExecutor> sExecutors = Maps.newHashMap();
     36 
     37     public static ProviderExecutor forAuthority(String authority) {
     38         synchronized (sExecutors) {
     39             ProviderExecutor executor = sExecutors.get(authority);
     40             if (executor == null) {
     41                 executor = new ProviderExecutor();
     42                 executor.setName("ProviderExecutor: " + authority);
     43                 executor.start();
     44                 sExecutors.put(authority, executor);
     45             }
     46             return executor;
     47         }
     48     }
     49 
     50     public interface Preemptable {
     51         void preempt();
     52     }
     53 
     54     private final LinkedBlockingQueue<Runnable> mQueue = new LinkedBlockingQueue<Runnable>();
     55 
     56     private final ArrayList<WeakReference<Preemptable>> mPreemptable = Lists.newArrayList();
     57 
     58     private void preempt() {
     59         synchronized (mPreemptable) {
     60             int count = 0;
     61             for (WeakReference<Preemptable> ref : mPreemptable) {
     62                 final Preemptable p = ref.get();
     63                 if (p != null) {
     64                     count++;
     65                     p.preempt();
     66                 }
     67             }
     68             mPreemptable.clear();
     69         }
     70     }
     71 
     72     /**
     73      * Execute the given task. If given task is not {@link Preemptable}, it will
     74      * preempt all outstanding preemptable tasks.
     75      */
     76     public <P> void execute(AsyncTask<P, ?, ?> task, P... params) {
     77         if (task instanceof Preemptable) {
     78             synchronized (mPreemptable) {
     79                 mPreemptable.add(new WeakReference<Preemptable>((Preemptable) task));
     80             }
     81             task.executeOnExecutor(mNonPreemptingExecutor, params);
     82         } else {
     83             task.executeOnExecutor(this, params);
     84         }
     85     }
     86 
     87     private Executor mNonPreemptingExecutor = new Executor() {
     88         @Override
     89         public void execute(Runnable command) {
     90             Preconditions.checkNotNull(command);
     91             mQueue.add(command);
     92         }
     93     };
     94 
     95     @Override
     96     public void execute(Runnable command) {
     97         preempt();
     98         Preconditions.checkNotNull(command);
     99         mQueue.add(command);
    100     }
    101 
    102     @Override
    103     public void run() {
    104         while (true) {
    105             try {
    106                 final Runnable command = mQueue.take();
    107                 command.run();
    108             } catch (InterruptedException e) {
    109                 // That was weird; let's go look for more tasks.
    110             }
    111         }
    112     }
    113 }
    114