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/*
* Copyright (C) 2007 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 android.os;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.WeakHashMap;
import java.util.Set;
import android.util.Log;
/**
* Helper class that helps you use IBinder objects as reference counted
* tokens. IBinders make good tokens because we find out when they are
* removed
*
*/
public abstract class TokenWatcher
{
/**
* Construct the TokenWatcher
*
* @param h A handler to call {@link #acquired} and {@link #released}
* on. If you don't care, just call it like this, although your thread
* will have to be a Looper thread.
* <code>new TokenWatcher(new Handler())</code>
* @param tag A debugging tag for this TokenWatcher
*/
public TokenWatcher(Handler h, String tag)
{
mHandler = h;
mTag = tag != null ? tag : "TokenWatcher";
}
/**
* Called when the number of active tokens goes from 0 to 1.
*/
public abstract void acquired();
/**
* Called when the number of active tokens goes from 1 to 0.
*/
public abstract void released();
/**
* Record that this token has been acquired. When acquire is called, and
* the current count is 0, the acquired method is called on the given
* handler.
*
* @param token An IBinder object. If this token has already been acquired,
* no action is taken.
* @param tag A string used by the {@link #dump} method for debugging,
* to see who has references.
*/
public void acquire(IBinder token, String tag)
{
synchronized (mTokens) {
// explicitly checked to avoid bogus sendNotification calls because
// of the WeakHashMap and the GC
int oldSize = mTokens.size();
Death d = new Death(token, tag);
try {
token.linkToDeath(d, 0);
} catch (RemoteException e) {
return;
}
mTokens.put(token, d);
if (oldSize == 0 && !mAcquired) {
sendNotificationLocked(true);
mAcquired = true;
}
}
}
public void cleanup(IBinder token, boolean unlink)
{
synchronized (mTokens) {
Death d = mTokens.remove(token);
if (unlink && d != null) {
d.token.unlinkToDeath(d, 0);
d.token = null;
}
if (mTokens.size() == 0 && mAcquired) {
sendNotificationLocked(false);
mAcquired = false;
}
}
}
public void release(IBinder token)
{
cleanup(token, true);
}
public boolean isAcquired()
{
synchronized (mTokens) {
return mAcquired;
}
}
public void dump()
{
ArrayList<String> a = dumpInternal();
for (String s : a) {
Log.i(mTag, s);
}
}
public void dump(PrintWriter pw) {
ArrayList<String> a = dumpInternal();
for (String s : a) {
pw.println(s);
}
}
private ArrayList<String> dumpInternal() {
ArrayList<String> a = new ArrayList<String>();
synchronized (mTokens) {
Set<IBinder> keys = mTokens.keySet();
a.add("Token count: " + mTokens.size());
int i = 0;
for (IBinder b: keys) {
a.add("[" + i + "] " + mTokens.get(b).tag + " - " + b);
i++;
}
}
return a;
}
private Runnable mNotificationTask = new Runnable() {
public void run()
{
int value;
synchronized (mTokens) {
value = mNotificationQueue;
mNotificationQueue = -1;
}
if (value == 1) {
acquired();
}
else if (value == 0) {
released();
}
}
};
private void sendNotificationLocked(boolean on)
{
int value = on ? 1 : 0;
if (mNotificationQueue == -1) {
// empty
mNotificationQueue = value;
mHandler.post(mNotificationTask);
}
else if (mNotificationQueue != value) {
// it's a pair, so cancel it
mNotificationQueue = -1;
mHandler.removeCallbacks(mNotificationTask);
}
// else, same so do nothing -- maybe we should warn?
}
private class Death implements IBinder.DeathRecipient
{
IBinder token;
String tag;
Death(IBinder token, String tag)
{
this.token = token;
this.tag = tag;
}
public void binderDied()
{
cleanup(token, false);
}
protected void finalize() throws Throwable
{
try {
if (token != null) {
Log.w(mTag, "cleaning up leaked reference: " + tag);
release(token);
}
}
finally {
super.finalize();
}
}
}
private WeakHashMap<IBinder,Death> mTokens = new WeakHashMap<IBinder,Death>();
private Handler mHandler;
private String mTag;
private int mNotificationQueue = -1;
private volatile boolean mAcquired = false;
}
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