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/*
* Copyright (C) 2013 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.documentsui;
import android.os.AsyncTask;
import com.android.internal.annotations.GuardedBy;
import com.android.internal.util.Preconditions;
import com.google.android.collect.Lists;
import com.google.android.collect.Maps;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.concurrent.Executor;
import java.util.concurrent.LinkedBlockingQueue;
public class ProviderExecutor extends Thread implements Executor {
@GuardedBy("sExecutors")
private static HashMap<String, ProviderExecutor> sExecutors = Maps.newHashMap();
public static ProviderExecutor forAuthority(String authority) {
synchronized (sExecutors) {
ProviderExecutor executor = sExecutors.get(authority);
if (executor == null) {
executor = new ProviderExecutor();
executor.setName("ProviderExecutor: " + authority);
executor.start();
sExecutors.put(authority, executor);
}
return executor;
}
}
public interface Preemptable {
void preempt();
}
private final LinkedBlockingQueue<Runnable> mQueue = new LinkedBlockingQueue<Runnable>();
private final ArrayList<WeakReference<Preemptable>> mPreemptable = Lists.newArrayList();
private void preempt() {
synchronized (mPreemptable) {
int count = 0;
for (WeakReference<Preemptable> ref : mPreemptable) {
final Preemptable p = ref.get();
if (p != null) {
count++;
p.preempt();
}
}
mPreemptable.clear();
}
}
/**
* Execute the given task. If given task is not {@link Preemptable}, it will
* preempt all outstanding preemptable tasks.
*/
public <P> void execute(AsyncTask<P, ?, ?> task, P... params) {
if (task instanceof Preemptable) {
synchronized (mPreemptable) {
mPreemptable.add(new WeakReference<Preemptable>((Preemptable) task));
}
task.executeOnExecutor(mNonPreemptingExecutor, params);
} else {
task.executeOnExecutor(this, params);
}
}
private Executor mNonPreemptingExecutor = new Executor() {
@Override
public void execute(Runnable command) {
Preconditions.checkNotNull(command);
mQueue.add(command);
}
};
@Override
public void execute(Runnable command) {
preempt();
Preconditions.checkNotNull(command);
mQueue.add(command);
}
@Override
public void run() {
while (true) {
try {
final Runnable command = mQueue.take();
command.run();
} catch (InterruptedException e) {
// That was weird; let's go look for more tasks.
}
}
}
}
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