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XSharedPreferences: implemented on-demand file watcher
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Further optimization of f8aa9d0
File watcher is initiated and kept alive only while there are valid watch keys present.
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@C3C0 @MlgmXyysd
C3C0 authored and MlgmXyysd committed Feb 6, 2021
1 parent 71b331e commit 08fae47
Showing 1 changed file with 91 additions and 68 deletions.
159 changes: 91 additions & 68 deletions xposed-bridge/src/main/java/de/robv/android/xposed/XSharedPreferences.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.AccessDeniedException;
import java.nio.file.ClosedWatchServiceException;
import java.nio.file.Path;
import java.nio.file.StandardWatchEventKinds;
import java.nio.file.WatchEvent;
Expand All @@ -38,9 +39,9 @@
*/
public final class XSharedPreferences implements SharedPreferences {
private static final String TAG = "XSharedPreferences";
private static final HashMap<Path, PrefsData> sInstances = new HashMap<>();
private static final HashMap<WatchKey, PrefsData> sWatcherKeyInstances = new HashMap<>();
private static final Object sContent = new Object();
private static Thread sDaemon = null;
private static Thread sWatcherDaemon = null;
private static WatchService sWatcher;

private final HashMap<OnSharedPreferenceChangeListener, Object> mListeners = new HashMap<>();
Expand All @@ -50,36 +51,19 @@ public final class XSharedPreferences implements SharedPreferences {
private boolean mLoaded = false;
private long mLastModified;
private long mFileSize;
private boolean mWatcherEnabled;

private static synchronized WatchService getWatcher() {
if (sWatcher == null) {
try {
sWatcher = new File(XposedInit.prefsBasePath).toPath().getFileSystem().newWatchService();
if (BuildConfig.DEBUG) Log.d(TAG, "Created WatchService instance");
} catch (IOException e) {
Log.e(TAG, "Failed to create WatchService", e);
}
}

if (sWatcher != null && (sDaemon == null || !sDaemon.isAlive())) {
initWatcherDaemon();
}

return sWatcher;
}
private WatchKey mWatchKey;

private static void initWatcherDaemon() {
sDaemon = new Thread() {
sWatcherDaemon = new Thread() {
@Override
public void run() {
Log.d(TAG, "Watcher daemon thread started");
if (BuildConfig.DEBUG) Log.d(TAG, "Watcher daemon thread started");
while (true) {
WatchKey key;
try {
key = sWatcher.take();
} catch (InterruptedException ignored) {
return;
} catch (ClosedWatchServiceException | InterruptedException ignored) {
break;
}
for (WatchEvent<?> event : key.pollEvents()) {
WatchEvent.Kind<?> kind = event.kind();
Expand All @@ -94,14 +78,11 @@ public void run() {
if (pathStr.endsWith(".bak")) {
if (kind != StandardWatchEventKinds.ENTRY_DELETE) {
continue;
} else {
pathStr = path.getFileName().toString();
path = dir.resolve(pathStr.substring(0, pathStr.length() - 4));
}
} else if (SELinuxHelper.getAppDataFileService().checkFileExists(pathStr + ".bak")) {
continue;
}
PrefsData data = sInstances.get(path);
PrefsData data = sWatcherKeyInstances.get(key);
if (data != null && data.hasChanged()) {
for (OnSharedPreferenceChangeListener l : data.mPrefs.mListeners.keySet()) {
try {
Expand All @@ -114,35 +95,30 @@ public void run() {
}
key.reset();
}
sWatcherKeyInstances.clear();
try {
sWatcher.close();
} catch (IOException ignore) { }
sWatcher = null;
if (BuildConfig.DEBUG) Log.d(TAG, "Watcher daemon thread finished");
}
};
sDaemon.setName(TAG + "-Daemon");
sDaemon.setDaemon(true);
sDaemon.start();
sWatcherDaemon.setName(TAG + "-Daemon");
sWatcherDaemon.setDaemon(true);
sWatcherDaemon.start();
}

/**
* Read settings from the specified file.
*
* @param prefFile The file to read the preferences from.
* @param enableWatcher Whether to enable support for preference change listeners
*/
public XSharedPreferences(File prefFile, boolean enableWatcher) {
public XSharedPreferences(File prefFile) {
mFile = prefFile;
mFilename = prefFile.getAbsolutePath();
mWatcherEnabled = enableWatcher;
init();
}

/**
* Read settings from the specified file.
*
* @param prefFile The file to read the preferences from.
*/
public XSharedPreferences(File prefFile) {
this(prefFile, false);
}

/**
* Read settings from the default preferences for a package.
* These preferences are returned by {@link PreferenceManager#getDefaultSharedPreferences}.
Expand Down Expand Up @@ -179,7 +155,6 @@ public XSharedPreferences(String packageName, String prefFileName) {
xposedminversion = MetaDataReader.extractIntPart((String) minVersionRaw);
}
xposedsharedprefs = metaData.containsKey("xposedsharedprefs");
mWatcherEnabled = metaData.containsKey("xposedsharedprefswatcher");
}
} catch (NumberFormatException | IOException e) {
Log.w(TAG, "Apk parser fails: " + e);
Expand All @@ -197,26 +172,52 @@ public XSharedPreferences(String packageName, String prefFileName) {
}

private void tryRegisterWatcher() {
if (!mWatcherEnabled) {
if (mWatchKey != null && mWatchKey.isValid()) {
return;
}
Path path = mFile.toPath();
if (sInstances.containsKey(path)) {
return;

synchronized (sWatcherKeyInstances) {
Path path = mFile.toPath();
try {
if (sWatcher == null) {
sWatcher = new File(XposedInit.prefsBasePath).toPath().getFileSystem().newWatchService();
if (BuildConfig.DEBUG) Log.d(TAG, "Created WatchService instance");
}
mWatchKey = path.getParent().register(sWatcher, StandardWatchEventKinds.ENTRY_CREATE,
StandardWatchEventKinds.ENTRY_MODIFY, StandardWatchEventKinds.ENTRY_DELETE);
sWatcherKeyInstances.put(mWatchKey, new PrefsData(this));
if (sWatcherDaemon == null || !sWatcherDaemon.isAlive()) {
initWatcherDaemon();
}
if (BuildConfig.DEBUG) Log.d(TAG, "tryRegisterWatcher: registered file watcher for " + path);
} catch (AccessDeniedException accDeniedEx) {
if (BuildConfig.DEBUG) Log.e(TAG, "tryRegisterWatcher: access denied to " + path);
} catch (Exception e) {
Log.e(TAG, "tryRegisterWatcher: failed to register file watcher", e);
}
}
try {
path.getParent().register(getWatcher(), StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_MODIFY, StandardWatchEventKinds.ENTRY_DELETE);
sInstances.put(path, new PrefsData(this));
if (BuildConfig.DEBUG) Log.d(TAG, "tryRegisterWatcher: registered file watcher for " + path);
} catch (AccessDeniedException accDeniedEx) {
if (BuildConfig.DEBUG) Log.d(TAG, "tryRegisterWatcher: access denied to " + path);
} catch (Exception e) {
Log.d(TAG, "tryRegisterWatcher: failed to register file watcher", e);
}

private void tryUnregisterWatcher() {
synchronized (sWatcherKeyInstances) {
if (sWatcherKeyInstances.containsKey(mWatchKey)) {
mWatchKey.cancel();
sWatcherKeyInstances.remove(mWatchKey);
mWatchKey = null;
}
boolean atLeastOneValid = false;
for (WatchKey key : sWatcherKeyInstances.keySet()) {
atLeastOneValid |= key.isValid();
}
if (!atLeastOneValid) {
try {
sWatcher.close();
} catch (Exception ignore) { }
}
}
}

private void init() {
tryRegisterWatcher();
startLoadFromDisk();
}

Expand Down Expand Up @@ -266,7 +267,15 @@ public boolean makeWorldReadable() {
if (!mFile.setReadable(true, false))
return false;

tryRegisterWatcher();
// Watcher service needs read access to parent directory (looks like execute is not enough)
if (mFile.getParentFile() != null) {
mFile.getParentFile().setReadable(true, false);
}

if (mListeners.size() > 0) {
tryRegisterWatcher();
}

return true;
}

Expand Down Expand Up @@ -480,25 +489,39 @@ public Editor edit() {
throw new UnsupportedOperationException("read-only implementation");
}

@Deprecated
/**
* Registers a callback to be invoked when a change happens to a preference file.<br>
* Note that it is not possible to determine which preference changed exactly and thus
* preference key in callback invocation will always be null.
*
* @param listener The callback that will run.
* @see #unregisterOnSharedPreferenceChangeListener
*/
@Override
public void registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
if (!mWatcherEnabled)
throw new UnsupportedOperationException("File watcher feature is disabled for this instance");

synchronized(this) {
mListeners.put(listener, sContent);
if (listener != null && !mListeners.containsKey(listener)) {
mListeners.put(listener, sContent);
tryRegisterWatcher();
}
}
}

@Deprecated
/**
* Unregisters a previous callback.
*
* @param listener The callback that should be unregistered.
* @see #registerOnSharedPreferenceChangeListener
*/
@Override
public void unregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
if (!mWatcherEnabled)
throw new UnsupportedOperationException("File watcher feature is disabled for this instance");

synchronized(this) {
mListeners.remove(listener);
if (mListeners.containsKey(listener)) {
mListeners.remove(listener);
if (mListeners.size() == 0) {
tryUnregisterWatcher();
}
}
}
}

Expand Down

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