Optimized preference file changes detection mechanism

Optimizations on top of original idea by @XspeedPL.

- introduced new manifest parameter: xposedsharedprefswatcher
- file watcher daemon starts only in case there is at least one module in the hooked process that requested file watcher feature either by specification in the
manifest or using new constructor XSharedPreferences(file, enableWatcher)
- XSharedPreferences instance registers watcher events only when it has support for watcher enabled so even if watcher daemon is already running
due to request by other module, it won't watch for events on files that belong to XSharedPreferences instance that has watcher disabled
- reduced log ouput in case of release builds

xposed-bridge/build.gradle

@@ -19,9 +19,11 @@ android {
             minifyEnabled true
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
             buildConfigField "int", "API_CODE", "$apiCode"
+            buildConfigField "boolean", "DEBUG", "false"
         }
         debug {
             buildConfigField "int", "API_CODE", "$apiCode"
+            buildConfigField "boolean", "DEBUG", "true"
         }
     }
 }

xposed-bridge/src/main/java/de/robv/android/xposed/XSharedPreferences.java

@@ -8,6 +8,7 @@ import android.preference.PreferenceManager;
 import android.util.Log;
 
 import com.android.internal.util.XmlUtils;
+import com.elderdrivers.riru.edxp.bridge.BuildConfig;
 import com.elderdrivers.riru.edxp.util.MetaDataReader;
 
 import org.xmlpull.v1.XmlPullParserException;
@@ -16,6 +17,7 @@ import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.file.AccessDeniedException;
 import java.nio.file.Path;
 import java.nio.file.StandardWatchEventKinds;
 import java.nio.file.WatchEvent;
@@ -36,10 +38,11 @@ import de.robv.android.xposed.services.FileResult;
  */
 public final class XSharedPreferences implements SharedPreferences {
     private static final String TAG = "XSharedPreferences";
-    private static final HashMap<Path, PrefsData> mInstances = new HashMap<>();
+    private static final HashMap<Path, PrefsData> sInstances = new HashMap<>();
-    private static final Object mContent = new Object();
+    private static final Object sContent = new Object();
-    private static Thread mDaemon = null;
+    private static Thread sDaemon = null;
-    private static WatchService mWatcher;
+    private static WatchService sWatcher;
+
     private final HashMap<OnSharedPreferenceChangeListener, Object> mListeners = new HashMap<>();
     private final File mFile;
     private final String mFilename;
@@ -47,14 +50,88 @@ public final class XSharedPreferences implements SharedPreferences {
     private boolean mLoaded = false;
     private long mLastModified;
     private long mFileSize;
+    private boolean mWatcherEnabled;
 
-    static {
+    private static synchronized WatchService getWatcher() {
-        try {
+        if (sWatcher == null) {
-            mWatcher = new File(XposedInit.prefsBasePath).toPath().getFileSystem().newWatchService();
+            try {
-            Log.d(TAG, "Created WatchService instance");
+                sWatcher = new File(XposedInit.prefsBasePath).toPath().getFileSystem().newWatchService();
-        } catch (IOException e) {
+                if (BuildConfig.DEBUG) Log.d(TAG, "Created WatchService instance");
-            Log.e(TAG, "Failed to create WatchService", e);
+            } catch (IOException e) {
+                Log.e(TAG, "Failed to create WatchService", e);
+            }
         }
+
+        if (sWatcher != null && (sDaemon == null || !sDaemon.isAlive())) {
+            initWatcherDaemon();
+        }
+
+        return sWatcher;
+    }
+
+    private static void initWatcherDaemon() {
+        sDaemon = new Thread() {
+            @Override
+            public void run() {
+                Log.d(TAG, "Watcher daemon thread started");
+                while (true) {
+                    WatchKey key;
+                    try {
+                        key = sWatcher.take();
+                    } catch (InterruptedException ignored) {
+                        return;
+                    }
+                    for (WatchEvent<?> event : key.pollEvents()) {
+                        WatchEvent.Kind<?> kind = event.kind();
+                        if (kind == StandardWatchEventKinds.OVERFLOW) {
+                            continue;
+                        }
+                        Path dir = (Path) key.watchable();
+                        Path path = dir.resolve((Path) event.context());
+                        String pathStr = path.toString();
+                        if (BuildConfig.DEBUG) Log.v(TAG, "File " + path.toString() + " event: " + kind.name());
+                        // We react to both real and backup files due to rare race conditions
+                        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);
+                        if (data != null && data.hasChanged()) {
+                            for (OnSharedPreferenceChangeListener l : data.mPrefs.mListeners.keySet()) {
+                                try {
+                                    l.onSharedPreferenceChanged(data.mPrefs, null);
+                                } catch (Throwable t) {
+                                    if (BuildConfig.DEBUG) Log.e(TAG, "Fail in preference change listener", t);
+                                }
+                            }
+                        }
+                    }
+                    key.reset();
+                }
+            }
+        };
+        sDaemon.setName(TAG + "-Daemon");
+        sDaemon.setDaemon(true);
+        sDaemon.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) {
+        mFile = prefFile;
+        mFilename = prefFile.getAbsolutePath();
+        mWatcherEnabled = enableWatcher;
+        init();
     }
 
     /**
@@ -63,9 +140,7 @@ public final class XSharedPreferences implements SharedPreferences {
      * @param prefFile The file to read the preferences from.
      */
     public XSharedPreferences(File prefFile) {
-        mFile = prefFile;
+        this(prefFile, false);
-        mFilename = prefFile.getAbsolutePath();
-        init();
     }
 
     /**
@@ -104,6 +179,7 @@ public final class XSharedPreferences implements SharedPreferences {
                             xposedminversion = MetaDataReader.extractIntPart((String) minVersionRaw);
                         }
                         xposedsharedprefs = metaData.containsKey("xposedsharedprefs");
+                        mWatcherEnabled = metaData.containsKey("xposedsharedprefswatcher");
                     }
                 } catch (NumberFormatException | IOException e) {
                     Log.w(TAG, "Apk parser fails: " + e);
@@ -121,71 +197,25 @@ public final class XSharedPreferences implements SharedPreferences {
     }
 
     private void tryRegisterWatcher() {
+        if (!mWatcherEnabled) {
+            return;
+        }
         Path path = mFile.toPath();
-        if (mInstances.containsKey(path)) {
+        if (sInstances.containsKey(path)) {
             return;
         }
         try {
-            path.getParent().register(mWatcher, StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_MODIFY, StandardWatchEventKinds.ENTRY_DELETE);
+            path.getParent().register(getWatcher(), StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_MODIFY, StandardWatchEventKinds.ENTRY_DELETE);
-            mInstances.put(path, new PrefsData(this));
+            sInstances.put(path, new PrefsData(this));
-            Log.d(TAG, "Registered file watcher for " + path);
+            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, "Failed to register file watcher", e);
+            Log.d(TAG, "tryRegisterWatcher: failed to register file watcher", e);
         }
     }
 
     private void init() {
-        if (mDaemon == null || !mDaemon.isAlive()) {
-            mDaemon = new Thread() {
-                @Override
-                public void run() {
-                    Log.d(TAG, "Daemon thread started");
-                    while (true) {
-                        WatchKey key;
-                        try {
-                            key = mWatcher.take();
-                        } catch (InterruptedException ignored) {
-                            return;
-                        }
-                        for (WatchEvent<?> event : key.pollEvents()) {
-                            WatchEvent.Kind<?> kind = event.kind();
-                            if (kind == StandardWatchEventKinds.OVERFLOW) {
-                                continue;
-                            }
-                            Path dir = (Path)key.watchable();
-                            Path path = dir.resolve((Path)event.context());
-                            String pathStr = path.toString();
-                            Log.v(TAG, "File " + path.toString() + " event: " + kind.name());
-                            // We react to both real and backup files due to rare race conditions
-                            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 = mInstances.get(path);
-                            if (data != null && data.hasChanged()) {
-                                for (OnSharedPreferenceChangeListener l : data.mPrefs.mListeners.keySet()) {
-                                    try {
-                                        l.onSharedPreferenceChanged(data.mPrefs, null);
-                                    } catch (Throwable t) {
-                                        Log.e(TAG, "Fail in preference change listener", t);
-                                    }
-                                }
-                            }
-                        }
-                        key.reset();
-                    }
-                }
-            };
-            mDaemon.setName(TAG + "-Daemon");
-            mDaemon.setDaemon(true);
-            mDaemon.start();
-        }
         tryRegisterWatcher();
         startLoadFromDisk();
     }
@@ -454,7 +484,7 @@ public final class XSharedPreferences implements SharedPreferences {
     @Override
     public void registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
         synchronized(this) {
-            mListeners.put(listener, mContent);
+            mListeners.put(listener, sContent);
         }
     }
 
@@ -480,22 +510,22 @@ public final class XSharedPreferences implements SharedPreferences {
         public boolean hasChanged() {
             long size = tryGetFileSize(mPrefs.mFilename);
             if (size < 1) {
-                Log.d(TAG, "Ignoring empty prefs file");
+                if (BuildConfig.DEBUG) Log.d(TAG, "Ignoring empty prefs file");
                 return false;
             }
             if (size != mSize) {
                 mSize = size;
                 mHash = tryGetFileHash(mPrefs.mFilename);
-                Log.d(TAG, "Prefs file size changed");
+                if (BuildConfig.DEBUG) Log.d(TAG, "Prefs file size changed");
                 return true;
             }
             byte[] hash = tryGetFileHash(mPrefs.mFilename);
             if (!Arrays.equals(hash, mHash)) {
                 mHash = hash;
-                Log.d(TAG, "Prefs file hash changed");
+                if (BuildConfig.DEBUG) Log.d(TAG, "Prefs file hash changed");
                 return true;
             }
-            Log.d(TAG, "Prefs file not changed");
+            if (BuildConfig.DEBUG) Log.d(TAG, "Prefs file not changed");
             return false;
         }
     }