/*
* Copyright (C) 2008 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 android.util.Log;
import java.util.ArrayList;
import java.util.HashMap;
/**
* UEventObserver is an abstract class that receives UEvent's from the kernel.<p>
*
* Subclass UEventObserver, implementing onUEvent(UEvent event), then call
* startObserving() with a match string. The UEvent thread will then call your
* onUEvent() method when a UEvent occurs that contains your match string.<p>
*
* Call stopObserving() to stop receiving UEvent's.<p>
*
* There is only one UEvent thread per process, even if that process has
* multiple UEventObserver subclass instances. The UEvent thread starts when
* the startObserving() is called for the first time in that process. Once
* started the UEvent thread will not stop (although it can stop notifying
* UEventObserver's via stopObserving()).<p>
*
* @hide
*/
public abstract class UEventObserver {
private static final String TAG = "UEventObserver";
private static final boolean DEBUG = false;
private static UEventThread sThread;
private static native void nativeSetup();
private static native String nativeWaitForNextEvent();
private static native void nativeAddMatch(String match);
private static native void nativeRemoveMatch(String match);
public UEventObserver() {
}
@Override
protected void finalize() throws Throwable {
try {
stopObserving();
} finally {
super.finalize();
}
}
private static UEventThread getThread() {
synchronized (UEventObserver.class) {
if (sThread == null) {
sThread = new UEventThread();
sThread.start();
}
return sThread;
}
}
private static UEventThread peekThread() {
synchronized (UEventObserver.class) {
return sThread;
}
}
/**
* Begin observation of UEvent's.<p>
* This method will cause the UEvent thread to start if this is the first
* invocation of startObserving in this process.<p>
* Once called, the UEvent thread will call onUEvent() when an incoming
* UEvent matches the specified string.<p>
* This method can be called multiple times to register multiple matches.
* Only one call to stopObserving is required even with multiple registered
* matches.
*
* @param match A substring of the UEvent to match. Try to be as specific
* as possible to avoid incurring unintended additional cost from processing
* irrelevant messages. Netlink messages can be moderately high bandwidth and
* are expensive to parse. For example, some devices may send one netlink message
* for each vsync period.
*/
public final void startObserving(String match) {
if (match == null || match.isEmpty()) {
throw new IllegalArgumentException("match substring must be non-empty");
}
final UEventThread t = getThread();
t.addObserver(match, this);
}
/**
* End observation of UEvent's.<p>
* This process's UEvent thread will never call onUEvent() on this
* UEventObserver after this call. Repeated calls have no effect.
*/
public final void stopObserving() {
final UEventThread t = getThread();
if (t != null) {
t.removeObserver(this);
}
}
/**
* Subclasses of UEventObserver should override this method to handle
* UEvents.
*/
public abstract void onUEvent(UEvent event);
/**
* Representation of a UEvent.
*/
public static final class UEvent {
// collection of key=value pairs parsed from the uevent message
private final HashMap<String,String> mMap = new HashMap<String,String>();
public UEvent(String message) {
int offset = 0;
int length = message.length();
while (offset < length) {
int equals = message.indexOf('=', offset);
int at = message.indexOf('\0', offset);
if (at < 0) break;
if (equals > offset && equals < at) {
// key is before the equals sign, and value is after
mMap.put(message.substring(offset, equals),
message.substring(equals + 1, at));
}
offset = at + 1;
}
}
public String get(String key) {
return mMap.get(key);
}
public String get(String key, String defaultValue) {
String result = mMap.get(key);
return (result == null ? defaultValue : result);
}
public String toString() {
return mMap.toString();
}
}
private static final class UEventThread extends Thread {
/** Many to many mapping of string match to observer.
* Multimap would be better, but not available in android, so use
* an ArrayList where even elements are the String match and odd
* elements the corresponding UEventObserver observer */
private final ArrayList<Object> mKeysAndObservers = new ArrayList<Object>();
private final ArrayList<UEventObserver> mTempObserversToSignal =
new ArrayList<UEventObserver>();
public UEventThread() {
super("UEventObserver");
}
@Override
public void run() {
nativeSetup();
while (true) {
String message = nativeWaitForNextEvent();
if (message != null) {
if (DEBUG) {
Log.d(TAG, message);
}
sendEvent(message);
}
}
}
private void sendEvent(String message) {
synchronized (mKeysAndObservers) {
final int N = mKeysAndObservers.size();
for (int i = 0; i < N; i += 2) {
final String key = (String)mKeysAndObservers.get(i);
if (message.contains(key)) {
final UEventObserver observer =
(UEventObserver)mKeysAndObservers.get(i + 1);
mTempObserversToSignal.add(observer);
}
}
}
if (!mTempObserversToSignal.isEmpty()) {
final UEvent event = new UEvent(message);
final int N = mTempObserversToSignal.size();
for (int i = 0; i < N; i++) {
final UEventObserver observer = mTempObserversToSignal.get(i);
observer.onUEvent(event);
}
mTempObserversToSignal.clear();
}
}
public void addObserver(String match, UEventObserver observer) {
synchronized (mKeysAndObservers) {
mKeysAndObservers.add(match);
mKeysAndObservers.add(observer);
nativeAddMatch(match);
}
}
/** Removes every key/value pair where value=observer from mObservers */
public void removeObserver(UEventObserver observer) {
synchronized (mKeysAndObservers) {
for (int i = 0; i < mKeysAndObservers.size(); ) {
if (mKeysAndObservers.get(i + 1) == observer) {
mKeysAndObservers.remove(i + 1);
final String match = (String)mKeysAndObservers.remove(i);
nativeRemoveMatch(match);
} else {
i += 2;
}
}
}
}
}
}
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