Only persist last Shared Preferences state (2f1bb852) · Commits · e / os / android_frameworks_base

core/java/android/app/SharedPreferencesImpl.java

+60 −12

Original line number	Diff line number	Diff line
		@@ -26,6 +26,8 @@ import android.system.StructStat;
		import android.util.Log;

		import com.google.android.collect.Maps;

		import com.android.internal.annotations.GuardedBy;
		import com.android.internal.util.XmlUtils;

		import dalvik.system.BlockGuard;
		@@ -72,6 +74,14 @@ final class SharedPreferencesImpl implements SharedPreferences {
		private final WeakHashMap<OnSharedPreferenceChangeListener, Object> mListeners =
		new WeakHashMap<OnSharedPreferenceChangeListener, Object>();

		/** Current memory state (always increasing) */
		@GuardedBy("this")
		private long mCurrentMemoryStateGeneration;

		/** Latest memory state that was committed to disk */
		@GuardedBy("mWritingToDiskLock")
		private long mDiskStateGeneration;

		SharedPreferencesImpl(File file, int mode) {
		mFile = file;
		mBackupFile = makeBackupFile(file);
		@@ -289,7 +299,7 @@ final class SharedPreferencesImpl implements SharedPreferences {

		// Return value from EditorImpl#commitToMemory()
		private static class MemoryCommitResult {
		public boolean changesMade; // any keys different?
		public long memoryStateGeneration;
		public List<String> keysModified; // may be null
		public Set<OnSharedPreferenceChangeListener> listeners; // may be null
		public Map<?, ?> mapToWriteToDisk;
		@@ -412,9 +422,11 @@ final class SharedPreferencesImpl implements SharedPreferences {
		}

		synchronized (this) {
		boolean changesMade = false;

		if (mClear) {
		if (!mMap.isEmpty()) {
		mcr.changesMade = true;
		changesMade = true;
		mMap.clear();
		}
		mClear = false;
		@@ -441,13 +453,19 @@ final class SharedPreferencesImpl implements SharedPreferences {
		mMap.put(k, v);
		}

		mcr.changesMade = true;
		changesMade = true;
		if (hasListeners) {
		mcr.keysModified.add(k);
		}
		}

		mModified.clear();

		if (changesMade) {
		mCurrentMemoryStateGeneration++;
		}

		mcr.memoryStateGeneration = mCurrentMemoryStateGeneration;
		}
		}
		return mcr;
		@@ -509,10 +527,12 @@ final class SharedPreferencesImpl implements SharedPreferences {
		*/
		private void enqueueDiskWrite(final MemoryCommitResult mcr,
		final Runnable postWriteRunnable) {
		final boolean isFromSyncCommit = (postWriteRunnable == null);

		final Runnable writeToDiskRunnable = new Runnable() {
		public void run() {
		synchronized (mWritingToDiskLock) {
		writeToFile(mcr);
		writeToFile(mcr, isFromSyncCommit);
		}
		synchronized (SharedPreferencesImpl.this) {
		mDiskWritesInFlight--;
		@@ -523,8 +543,6 @@ final class SharedPreferencesImpl implements SharedPreferences {
		}
		};

		final boolean isFromSyncCommit = (postWriteRunnable == null);

		// Typical #commit() path with fewer allocations, doing a write on
		// the current thread.
		if (isFromSyncCommit) {
		@@ -538,6 +556,10 @@ final class SharedPreferencesImpl implements SharedPreferences {
		}
		}

		if (DEBUG) {
		Log.d(TAG, "added " + mcr.memoryStateGeneration + " -> " + mFile.getName());
		}

		QueuedWork.singleThreadExecutor().execute(writeToDiskRunnable);
		}

		@@ -565,17 +587,34 @@ final class SharedPreferencesImpl implements SharedPreferences {
		}

		// Note: must hold mWritingToDiskLock
		private void writeToFile(MemoryCommitResult mcr) {
		private void writeToFile(MemoryCommitResult mcr, boolean isFromSyncCommit) {
		// Rename the current file so it may be used as a backup during the next read
		if (mFile.exists()) {
		if (!mcr.changesMade) {
		// If the file already exists, but no changes were
		// made to the underlying map, it's wasteful to
		// re-write the file. Return as if we wrote it
		// out.
		boolean needsWrite = false;

		if (isFromSyncCommit) {
		// Only need to write if the disk state is older than this commit
		if (mDiskStateGeneration < mcr.memoryStateGeneration) {
		needsWrite = true;
		}
		} else {
		synchronized (this) {
		// No need to persist intermediate states. Just wait for the latest state to be
		// persisted.
		if (mCurrentMemoryStateGeneration == mcr.memoryStateGeneration) {
		needsWrite = true;
		}
		}
		}

		if (!needsWrite) {
		if (DEBUG) {
		Log.d(TAG, "skipped " + mcr.memoryStateGeneration + " -> " + mFile.getName());
		}
		mcr.setDiskWriteResult(true);
		return;
		}

		if (!mBackupFile.exists()) {
		if (!mFile.renameTo(mBackupFile)) {
		Log.e(TAG, "Couldn't rename file " + mFile
		@@ -599,6 +638,11 @@ final class SharedPreferencesImpl implements SharedPreferences {
		}
		XmlUtils.writeMapXml(mcr.mapToWriteToDisk, str);
		FileUtils.sync(str);

		if (DEBUG) {
		Log.d(TAG, "wrote " + mcr.memoryStateGeneration + " -> " + mFile.getName());
		}

		str.close();
		ContextImpl.setFilePermissionsFromMode(mFile.getPath(), mMode, 0);
		try {
		@@ -612,7 +656,11 @@ final class SharedPreferencesImpl implements SharedPreferences {
		}
		// Writing was successful, delete the backup file if there is one.
		mBackupFile.delete();

		mDiskStateGeneration = mcr.memoryStateGeneration;

		mcr.setDiskWriteResult(true);

		return;
		} catch (XmlPullParserException e) {
		Log.w(TAG, "writeToFile: Got exception:", e);