/*
* Copyright (C) 2010 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.app;
import android.annotation.Nullable;
import android.content.SharedPreferences;
import android.os.FileUtils;
import android.os.Looper;
import android.system.ErrnoException;
import android.system.Os;
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.ExponentiallyBucketedHistogram;
import com.android.internal.util.XmlUtils;
import dalvik.system.BlockGuard;
import org.xmlpull.v1.XmlPullParserException;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.WeakHashMap;
import java.util.concurrent.CountDownLatch;
import libcore.io.IoUtils;
final class SharedPreferencesImpl implements SharedPreferences {
private static final String TAG = "SharedPreferencesImpl";
private static final boolean DEBUG = false;
private static final Object CONTENT = new Object();
/** If a fsync takes more than {@value #MAX_FSYNC_DURATION_MILLIS} ms, warn */
private static final long MAX_FSYNC_DURATION_MILLIS = 256;
// Lock ordering rules:
// - acquire SharedPreferencesImpl.mLock before EditorImpl.mLock
// - acquire mWritingToDiskLock before EditorImpl.mLock
private final File mFile;
private final File mBackupFile;
private final int mMode;
private final Object mLock = new Object();
private final Object mWritingToDiskLock = new Object();
@GuardedBy("mLock")
private Map<String, Object> mMap;
@GuardedBy("mLock")
private int mDiskWritesInFlight = 0;
@GuardedBy("mLock")
private boolean mLoaded = false;
@GuardedBy("mLock")
private long mStatTimestamp;
@GuardedBy("mLock")
private long mStatSize;
@GuardedBy("mLock")
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;
/** Time (and number of instances) of file-system sync requests */
@GuardedBy("mWritingToDiskLock")
private final ExponentiallyBucketedHistogram mSyncTimes = new ExponentiallyBucketedHistogram(16);
private int mNumSync = 0;
SharedPreferencesImpl(File file, int mode) {
mFile = file;
mBackupFile = makeBackupFile(file);
mMode = mode;
mLoaded = false;
mMap = null;
startLoadFromDisk();
}
private void startLoadFromDisk() {
synchronized (mLock) {
mLoaded = false;
}
new Thread("SharedPreferencesImpl-load") {
public void run() {
loadFromDisk();
}
}.start();
}
private void loadFromDisk() {
synchronized (mLock) {
if (mLoaded) {
return;
}
if (mBackupFile.exists()) {
mFile.delete();
mBackupFile.renameTo(mFile);
}
}
// Debugging
if (mFile.exists() && !mFile.canRead()) {
Log.w(TAG, "Attempt to read preferences file " + mFile + " without permission");
}
Map map = null;
StructStat stat = null;
try {
stat = Os.stat(mFile.getPath());
if (mFile.canRead()) {
BufferedInputStream str = null;
try {
str = new BufferedInputStream(
new FileInputStream(mFile), 16*1024);
map = XmlUtils.readMapXml(str);
} catch (Exception e) {
Log.w(TAG, "Cannot read " + mFile.getAbsolutePath(), e);
} finally {
IoUtils.closeQuietly(str);
}
}
} catch (ErrnoException e) {
/* ignore */
}
synchronized (mLock) {
mLoaded = true;
if (map != null) {
mMap = map;
mStatTimestamp = stat.st_mtime;
mStatSize = stat.st_size;
} else {
mMap = new HashMap<>();
}
mLock.notifyAll();
}
}
static File makeBackupFile(File prefsFile) {
return new File(prefsFile.getPath() + ".bak");
}
void startReloadIfChangedUnexpectedly() {
synchronized (mLock) {
// TODO: wait for any pending writes to disk?
if (!hasFileChangedUnexpectedly()) {
return;
}
startLoadFromDisk();
}
}
// Has the file changed out from under us? i.e. writes that
// we didn't instigate.
private boolean hasFileChangedUnexpectedly() {
synchronized (mLock) {
if (mDiskWritesInFlight > 0) {
// If we know we caused it, it's not unexpected.
if (DEBUG) Log.d(TAG, "disk write in flight, not unexpected.");
return false;
}
}
final StructStat stat;
try {
/*
* Metadata operations don't usually count as a block guard
* violation, but we explicitly want this one.
*/
BlockGuard.getThreadPolicy().onReadFromDisk();
stat = Os.stat(mFile.getPath());
} catch (ErrnoException e) {
return true;
}
synchronized (mLock) {
return mStatTimestamp != stat.st_mtime || mStatSize != stat.st_size;
}
}
public void registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
synchronized(mLock) {
mListeners.put(listener, CONTENT);
}
}
public void unregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
synchronized(mLock) {
mListeners.remove(listener);
}
}
private void awaitLoadedLocked() {
if (!mLoaded) {
// Raise an explicit StrictMode onReadFromDisk for this
// thread, since the real read will be in a different
// thread and otherwise ignored by StrictMode.
BlockGuard.getThreadPolicy().onReadFromDisk();
}
while (!mLoaded) {
try {
mLock.wait();
} catch (InterruptedException unused) {
}
}
}
public Map<String, ?> getAll() {
synchronized (mLock) {
awaitLoadedLocked();
//noinspection unchecked
return new HashMap<String, Object>(mMap);
}
}
@Nullable
public String getString(String key, @Nullable String defValue) {
synchronized (mLock) {
awaitLoadedLocked();
String v = (String)mMap.get(key);
return v != null ? v : defValue;
}
}
@Nullable
public Set<String> getStringSet(String key, @Nullable Set<String> defValues) {
synchronized (mLock) {
awaitLoadedLocked();
Set<String> v = (Set<String>) mMap.get(key);
return v != null ? v : defValues;
}
}
public int getInt(String key, int defValue) {
synchronized (mLock) {
awaitLoadedLocked();
Integer v = (Integer)mMap.get(key);
return v != null ? v : defValue;
}
}
public long getLong(String key, long defValue) {
synchronized (mLock) {
awaitLoadedLocked();
Long v = (Long)mMap.get(key);
return v != null ? v : defValue;
}
}
public float getFloat(String key, float defValue) {
synchronized (mLock) {
awaitLoadedLocked();
Float v = (Float)mMap.get(key);
return v != null ? v : defValue;
}
}
public boolean getBoolean(String key, boolean defValue) {
synchronized (mLock) {
awaitLoadedLocked();
Boolean v = (Boolean)mMap.get(key);
return v != null ? v : defValue;
}
}
public boolean contains(String key) {
synchronized (mLock) {
awaitLoadedLocked();
return mMap.containsKey(key);
}
}
public Editor edit() {
// TODO: remove the need to call awaitLoadedLocked() when
// requesting an editor. will require some work on the
// Editor, but then we should be able to do:
//
// context.getSharedPreferences(..).edit().putString(..).apply()
//
// ... all without blocking.
synchronized (mLock) {
awaitLoadedLocked();
}
return new EditorImpl();
}
// Return value from EditorImpl#commitToMemory()
private static class MemoryCommitResult {
final long memoryStateGeneration;
@Nullable final List<String> keysModified;
@Nullable final Set<OnSharedPreferenceChangeListener> listeners;
final Map<String, Object> mapToWriteToDisk;
final CountDownLatch writtenToDiskLatch = new CountDownLatch(1);
@GuardedBy("mWritingToDiskLock")
volatile boolean writeToDiskResult = false;
boolean wasWritten = false;
private MemoryCommitResult(long memoryStateGeneration, @Nullable List<String> keysModified,
@Nullable Set<OnSharedPreferenceChangeListener> listeners,
Map<String, Object> mapToWriteToDisk) {
this.memoryStateGeneration = memoryStateGeneration;
this.keysModified = keysModified;
this.listeners = listeners;
this.mapToWriteToDisk = mapToWriteToDisk;
}
void setDiskWriteResult(boolean wasWritten, boolean result) {
this.wasWritten = wasWritten;
writeToDiskResult = result;
writtenToDiskLatch.countDown();
}
}
public final class EditorImpl implements Editor {
private final Object mLock = new Object();
@GuardedBy("mLock")
private final Map<String, Object> mModified = Maps.newHashMap();
@GuardedBy("mLock")
private boolean mClear = false;
public Editor putString(String key, @Nullable String value) {
synchronized (mLock) {
mModified.put(key, value);
return this;
}
}
public Editor putStringSet(String key, @Nullable Set<String> values) {
synchronized (mLock) {
mModified.put(key,
(values == null) ? null : new HashSet<String>(values));
return this;
}
}
public Editor putInt(String key, int value) {
synchronized (mLock) {
mModified.put(key, value);
return this;
}
}
public Editor putLong(String key, long value) {
synchronized (mLock) {
mModified.put(key, value);
return this;
}
}
public Editor putFloat(String key, float value) {
synchronized (mLock) {
mModified.put(key, value);
return this;
}
}
public Editor putBoolean(String key, boolean value) {
synchronized (mLock) {
mModified.put(key, value);
return this;
}
}
public Editor remove(String key) {
synchronized (mLock) {
mModified.put(key, this);
return this;
}
}
public Editor clear() {
synchronized (mLock) {
mClear = true;
return this;
}
}
public void apply() {
final long startTime = System.currentTimeMillis();
final MemoryCommitResult mcr = commitToMemory();
final Runnable awaitCommit = new Runnable() {
public void run() {
try {
mcr.writtenToDiskLatch.await();
} catch (InterruptedException ignored) {
}
if (DEBUG && mcr.wasWritten) {
Log.d(TAG, mFile.getName() + ":" + mcr.memoryStateGeneration
+ " applied after " + (System.currentTimeMillis() - startTime)
+ " ms");
}
}
};
QueuedWork.addFinisher(awaitCommit);
Runnable postWriteRunnable = new Runnable() {
public void run() {
awaitCommit.run();
QueuedWork.removeFinisher(awaitCommit);
}
};
SharedPreferencesImpl.this.enqueueDiskWrite(mcr, postWriteRunnable);
// Okay to notify the listeners before it's hit disk
// because the listeners should always get the same
// SharedPreferences instance back, which has the
// changes reflected in memory.
notifyListeners(mcr);
}
// Returns true if any changes were made
private MemoryCommitResult commitToMemory() {
long memoryStateGeneration;
List<String> keysModified = null;
Set<OnSharedPreferenceChangeListener> listeners = null;
Map<String, Object> mapToWriteToDisk;
synchronized (SharedPreferencesImpl.this.mLock) {
// We optimistically don't make a deep copy until
// a memory commit comes in when we're already
// writing to disk.
if (mDiskWritesInFlight > 0) {
// We can't modify our mMap as a currently
// in-flight write owns it. Clone it before
// modifying it.
// noinspection unchecked
mMap = new HashMap<String, Object>(mMap);
}
mapToWriteToDisk = mMap;
mDiskWritesInFlight++;
boolean hasListeners = mListeners.size() > 0;
if (hasListeners) {
keysModified = new ArrayList<String>();
listeners = new HashSet<OnSharedPreferenceChangeListener>(mListeners.keySet());
}
synchronized (mLock) {
boolean changesMade = false;
if (mClear) {
if (!mMap.isEmpty()) {
changesMade = true;
mMap.clear();
}
mClear = false;
}
for (Map.Entry<String, Object> e : mModified.entrySet()) {
String k = e.getKey();
Object v = e.getValue();
// "this" is the magic value for a removal mutation. In addition,
// setting a value to "null" for a given key is specified to be
// equivalent to calling remove on that key.
if (v == this || v == null) {
if (!mMap.containsKey(k)) {
continue;
}
mMap.remove(k);
} else {
if (mMap.containsKey(k)) {
Object existingValue = mMap.get(k);
if (existingValue != null && existingValue.equals(v)) {
continue;
}
}
mMap.put(k, v);
}
changesMade = true;
if (hasListeners) {
keysModified.add(k);
}
}
mModified.clear();
if (changesMade) {
mCurrentMemoryStateGeneration++;
}
memoryStateGeneration = mCurrentMemoryStateGeneration;
}
}
return new MemoryCommitResult(memoryStateGeneration, keysModified, listeners,
mapToWriteToDisk);
}
public boolean commit() {
long startTime = 0;
if (DEBUG) {
startTime = System.currentTimeMillis();
}
MemoryCommitResult mcr = commitToMemory();
SharedPreferencesImpl.this.enqueueDiskWrite(
mcr, null /* sync write on this thread okay */);
try {
mcr.writtenToDiskLatch.await();
} catch (InterruptedException e) {
return false;
} finally {
if (DEBUG) {
Log.d(TAG, mFile.getName() + ":" + mcr.memoryStateGeneration
+ " committed after " + (System.currentTimeMillis() - startTime)
+ " ms");
}
}
notifyListeners(mcr);
return mcr.writeToDiskResult;
}
private void notifyListeners(final MemoryCommitResult mcr) {
if (mcr.listeners == null || mcr.keysModified == null ||
mcr.keysModified.size() == 0) {
return;
}
if (Looper.myLooper() == Looper.getMainLooper()) {
for (int i = mcr.keysModified.size() - 1; i >= 0; i--) {
final String key = mcr.keysModified.get(i);
for (OnSharedPreferenceChangeListener listener : mcr.listeners) {
if (listener != null) {
listener.onSharedPreferenceChanged(SharedPreferencesImpl.this, key);
}
}
}
} else {
// Run this function on the main thread.
ActivityThread.sMainThreadHandler.post(new Runnable() {
public void run() {
notifyListeners(mcr);
}
});
}
}
}
/**
* Enqueue an already-committed-to-memory result to be written
* to disk.
*
* They will be written to disk one-at-a-time in the order
* that they're enqueued.
*
* @param postWriteRunnable if non-null, we're being called
* from apply() and this is the runnable to run after
* the write proceeds. if null (from a regular commit()),
* then we're allowed to do this disk write on the main
* thread (which in addition to reducing allocations and
* creating a background thread, this has the advantage that
* we catch them in userdebug StrictMode reports to convert
* them where possible to apply() ...)
*/
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, isFromSyncCommit);
}
synchronized (mLock) {
mDiskWritesInFlight--;
}
if (postWriteRunnable != null) {
postWriteRunnable.run();
}
}
};
// Typical #commit() path with fewer allocations, doing a write on
// the current thread.
if (isFromSyncCommit) {
boolean wasEmpty = false;
synchronized (mLock) {
wasEmpty = mDiskWritesInFlight == 1;
}
if (wasEmpty) {
writeToDiskRunnable.run();
return;
}
}
QueuedWork.queue(writeToDiskRunnable, !isFromSyncCommit);
}
private static FileOutputStream createFileOutputStream(File file) {
FileOutputStream str = null;
try {
str = new FileOutputStream(file);
} catch (FileNotFoundException e) {
File parent = file.getParentFile();
if (!parent.mkdir()) {
Log.e(TAG, "Couldn't create directory for SharedPreferences file " + file);
return null;
}
FileUtils.setPermissions(
parent.getPath(),
FileUtils.S_IRWXU|FileUtils.S_IRWXG|FileUtils.S_IXOTH,
-1, -1);
try {
str = new FileOutputStream(file);
} catch (FileNotFoundException e2) {
Log.e(TAG, "Couldn't create SharedPreferences file " + file, e2);
}
}
return str;
}
// Note: must hold mWritingToDiskLock
private void writeToFile(MemoryCommitResult mcr, boolean isFromSyncCommit) {
long startTime = 0;
long existsTime = 0;
long backupExistsTime = 0;
long outputStreamCreateTime = 0;
long writeTime = 0;
long fsyncTime = 0;
long setPermTime = 0;
long fstatTime = 0;
long deleteTime = 0;
if (DEBUG) {
startTime = System.currentTimeMillis();
}
boolean fileExists = mFile.exists();
if (DEBUG) {
existsTime = System.currentTimeMillis();
// Might not be set, hence init them to a default value
backupExistsTime = existsTime;
}
// Rename the current file so it may be used as a backup during the next read
if (fileExists) {
boolean needsWrite = false;
// Only need to write if the disk state is older than this commit
if (mDiskStateGeneration < mcr.memoryStateGeneration) {
if (isFromSyncCommit) {
needsWrite = true;
} else {
synchronized (mLock) {
// No need to persist intermediate states. Just wait for the latest state to
// be persisted.
if (mCurrentMemoryStateGeneration == mcr.memoryStateGeneration) {
needsWrite = true;
}
}
}
}
if (!needsWrite) {
mcr.setDiskWriteResult(false, true);
return;
}
boolean backupFileExists = mBackupFile.exists();
if (DEBUG) {
backupExistsTime = System.currentTimeMillis();
}
if (!backupFileExists) {
if (!mFile.renameTo(mBackupFile)) {
Log.e(TAG, "Couldn't rename file " + mFile
+ " to backup file " + mBackupFile);
mcr.setDiskWriteResult(false, false);
return;
}
} else {
mFile.delete();
}
}
// Attempt to write the file, delete the backup and return true as atomically as
// possible. If any exception occurs, delete the new file; next time we will restore
// from the backup.
try {
FileOutputStream str = createFileOutputStream(mFile);
if (DEBUG) {
outputStreamCreateTime = System.currentTimeMillis();
}
if (str == null) {
mcr.setDiskWriteResult(false, false);
return;
}
XmlUtils.writeMapXml(mcr.mapToWriteToDisk, str);
writeTime = System.currentTimeMillis();
FileUtils.sync(str);
fsyncTime = System.currentTimeMillis();
str.close();
ContextImpl.setFilePermissionsFromMode(mFile.getPath(), mMode, 0);
if (DEBUG) {
setPermTime = System.currentTimeMillis();
}
try {
final StructStat stat = Os.stat(mFile.getPath());
synchronized (mLock) {
mStatTimestamp = stat.st_mtime;
mStatSize = stat.st_size;
}
} catch (ErrnoException e) {
// Do nothing
}
if (DEBUG) {
fstatTime = System.currentTimeMillis();
}
// Writing was successful, delete the backup file if there is one.
mBackupFile.delete();
if (DEBUG) {
deleteTime = System.currentTimeMillis();
}
mDiskStateGeneration = mcr.memoryStateGeneration;
mcr.setDiskWriteResult(true, true);
if (DEBUG) {
Log.d(TAG, "write: " + (existsTime - startTime) + "/"
+ (backupExistsTime - startTime) + "/"
+ (outputStreamCreateTime - startTime) + "/"
+ (writeTime - startTime) + "/"
+ (fsyncTime - startTime) + "/"
+ (setPermTime - startTime) + "/"
+ (fstatTime - startTime) + "/"
+ (deleteTime - startTime));
}
long fsyncDuration = fsyncTime - writeTime;
mSyncTimes.add(Long.valueOf(fsyncDuration).intValue());
mNumSync++;
if (DEBUG || mNumSync % 1024 == 0 || fsyncDuration > MAX_FSYNC_DURATION_MILLIS) {
mSyncTimes.log(TAG, "Time required to fsync " + mFile + ": ");
}
return;
} catch (XmlPullParserException e) {
Log.w(TAG, "writeToFile: Got exception:", e);
} catch (IOException e) {
Log.w(TAG, "writeToFile: Got exception:", e);
}
// Clean up an unsuccessfully written file
if (mFile.exists()) {
if (!mFile.delete()) {
Log.e(TAG, "Couldn't clean up partially-written file " + mFile);
}
}
mcr.setDiskWriteResult(false, false);
}
}