/*
* Copyright (C) 2014 Divide.io
*
* 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 io.divide.shared.file;
import java.io.*;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.CountDownLatch;
public final class XmlStorage implements Storage {
private static final String TAG = "XmlStorage";
private static final boolean DEBUG = false;
// Lock ordering rules:
// - acquire XmlStorage.this before EditorImpl.this
// - acquire mWritingToDiskLock before EditorImpl.this
private final File mFile;
private final File mBackupFile;
private final int mMode;
private Map<String, Object> mMap; // guarded by 'this'
private int mDiskWritesInFlight = 0; // guarded by 'this'
private boolean mLoaded = false; // guarded by 'this'
private long mStatTimestamp; // guarded by 'this'
private long mStatSize; // guarded by 'this'
private final Object mWritingToDiskLock = new Object();
public XmlStorage(File file, int mode) {
mFile = file;
mBackupFile = makeBackupFile(file);
mMode = mode;
mLoaded = false;
mMap = null;
startLoadFromDisk();
}
private void startLoadFromDisk() {
synchronized (this) {
mLoaded = false;
}
new Thread("XmlStorage-load") {
public void run() {
synchronized (XmlStorage.this) {
loadFromDiskLocked();
}
}
}.start();
}
private void loadFromDiskLocked() {
if (mLoaded) {
return;
}
if (mBackupFile.exists()) {
mFile.delete();
mBackupFile.renameTo(mFile);
}
// Debugging
if (mFile.exists() && !mFile.canRead()) {
System.out.println("Attempt to read preferences file " + mFile + " without permission");
}
Map map = null;
// FileStatus stat = new FileStatus();
if (mFile.canRead()) {
try {
BufferedInputStream str = new BufferedInputStream(
new FileInputStream(mFile), 16*1024);
map = XmlUtils.readMapXml(str);
str.close();
} catch (FileNotFoundException e) {
System.out.print(e);
} catch (IOException e) {
System.out.print(e);
}
}
mLoaded = true;
if (map != null) {
mMap = map;
mStatTimestamp = mFile.lastModified();
mStatSize = mFile.length();
} else {
mMap = new HashMap<String, Object>();
}
notifyAll();
}
private static File makeBackupFile(File prefsFile) {
return new File(prefsFile.getPath() + ".bak");
}
void startReloadIfChangedUnexpectedly() {
synchronized (this) {
// 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 (this) {
if (mDiskWritesInFlight > 0) {
// If we know we caused it, it's not unexpected.
if (DEBUG) System.out.println( "disk write in flight, not unexpected.");
return false;
}
}
if (!mFile.canRead()) {
return true;
}
synchronized (this) {
return mStatTimestamp != mFile.lastModified() || mStatSize != mFile.length();
}
}
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 {
wait();
} catch (InterruptedException unused) {
}
}
}
public Map<String, ?> getAll() {
synchronized (this) {
awaitLoadedLocked();
//noinspection unchecked
return new HashMap<String, Object>(mMap);
}
}
public String getString(String key, String defValue) {
synchronized (this) {
awaitLoadedLocked();
String v = (String)mMap.get(key);
return v != null ? v : defValue;
}
}
public Set<String> getStringSet(String key, Set<String> defValues) {
synchronized (this) {
awaitLoadedLocked();
Set<String> v = (Set<String>) mMap.get(key);
return v != null ? v : defValues;
}
}
public int getInt(String key, int defValue) {
synchronized (this) {
awaitLoadedLocked();
Integer v = (Integer)mMap.get(key);
return v != null ? v : defValue;
}
}
public long getLong(String key, long defValue) {
synchronized (this) {
awaitLoadedLocked();
Long v = (Long)mMap.get(key);
return v != null ? v : defValue;
}
}
public float getFloat(String key, float defValue) {
synchronized (this) {
awaitLoadedLocked();
Float v = (Float)mMap.get(key);
return v != null ? v : defValue;
}
}
public boolean getBoolean(String key, boolean defValue) {
synchronized (this) {
awaitLoadedLocked();
Boolean v = (Boolean)mMap.get(key);
return v != null ? v : defValue;
}
}
public boolean contains(String key) {
synchronized (this) {
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 (this) {
awaitLoadedLocked();
}
return new EditorImpl();
}
// Return value from EditorImpl#commitToMemory()
private static class MemoryCommitResult {
public boolean changesMade; // any keys different?
public List<String> keysModified; // may be null
public Map<String, ?> mapToWriteToDisk;
public final CountDownLatch writtenToDiskLatch = new CountDownLatch(1);
public volatile boolean writeToDiskResult = false;
public void setDiskWriteResult(boolean result) {
writeToDiskResult = result;
writtenToDiskLatch.countDown();
}
}
public final class EditorImpl implements Editor {
private final Map<String, Object> mModified = new HashMap<String, Object>();
private boolean mClear = false;
public Editor putString(String key, String value) {
synchronized (this) {
mModified.put(key, value);
return this;
}
}
public Editor putStringSet(String key, Set<String> values) {
synchronized (this) {
mModified.put(key, values);
return this;
}
}
public Editor putInt(String key, int value) {
synchronized (this) {
mModified.put(key, value);
return this;
}
}
public Editor putLong(String key, long value) {
synchronized (this) {
mModified.put(key, value);
return this;
}
}
public Editor putFloat(String key, float value) {
synchronized (this) {
mModified.put(key, value);
return this;
}
}
public Editor putBoolean(String key, boolean value) {
synchronized (this) {
mModified.put(key, value);
return this;
}
}
public Editor remove(String key) {
synchronized (this) {
mModified.put(key, this);
return this;
}
}
public Editor clear() {
synchronized (this) {
mClear = true;
return this;
}
}
public void apply() {
final MemoryCommitResult mcr = commitToMemory();
final Runnable awaitCommit = new Runnable() {
public void run() {
try {
mcr.writtenToDiskLatch.await();
} catch (InterruptedException ignored) {
}
}
};
QueuedWork.add(awaitCommit);
Runnable postWriteRunnable = new Runnable() {
public void run() {
awaitCommit.run();
QueuedWork.remove(awaitCommit);
}
};
XmlStorage.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.
}
// Returns true if any changes were made
private MemoryCommitResult commitToMemory() {
MemoryCommitResult mcr = new MemoryCommitResult();
synchronized (XmlStorage.this) {
// 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);
}
mcr.mapToWriteToDisk = mMap;
mDiskWritesInFlight++;
synchronized (this) {
if (mClear) {
if (!mMap.isEmpty()) {
mcr.changesMade = true;
mMap.clear();
}
mClear = false;
}
for (Map.Entry<String, Object> e : mModified.entrySet()) {
String k = e.getKey();
Object v = e.getValue();
if (v == this) { // magic value for a removal mutation
if (!mMap.containsKey(k)) {
continue;
}
mMap.remove(k);
} else {
boolean isSame = false;
if (mMap.containsKey(k)) {
Object existingValue = mMap.get(k);
if (existingValue != null && existingValue.equals(v)) {
continue;
}
}
mMap.put(k, v);
}
mcr.changesMade = true;
}
mModified.clear();
}
}
return mcr;
}
public boolean commit() {
MemoryCommitResult mcr = commitToMemory();
XmlStorage.this.enqueueDiskWrite(
mcr, null /* sync write on this thread okay */);
try {
mcr.writtenToDiskLatch.await();
} catch (InterruptedException e) {
return false;
}
return mcr.writeToDiskResult;
}
}
/**
* 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 Runnable writeToDiskRunnable = new Runnable() {
public void run() {
synchronized (mWritingToDiskLock) {
writeToFile(mcr);
}
synchronized (XmlStorage.this) {
mDiskWritesInFlight--;
}
if (postWriteRunnable != null) {
postWriteRunnable.run();
}
}
};
final boolean isFromSyncCommit = (postWriteRunnable == null);
// Typical #commit() path with fewer allocations, doing a write on
// the current thread.
if (isFromSyncCommit) {
boolean wasEmpty = false;
synchronized (XmlStorage.this) {
wasEmpty = mDiskWritesInFlight == 1;
}
if (wasEmpty) {
writeToDiskRunnable.run();
return;
}
}
QueuedWork.singleThreadExecutor().execute(writeToDiskRunnable);
}
private static FileOutputStream createFileOutputStream(File file) {
FileOutputStream str = null;
try {
str = new FileOutputStream(file);
} catch (FileNotFoundException e) {
File parent = file.getParentFile();
if (!parent.mkdir()) {
System.err.println("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) {
System.err.println("Couldn't create SharedPreferences file " + file + ": " + e2);
}
}
return str;
}
// Note: must hold mWritingToDiskLock
private void writeToFile(MemoryCommitResult mcr) {
// 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.
mcr.setDiskWriteResult(true);
return;
}
if (!mBackupFile.exists()) {
if (!mFile.renameTo(mBackupFile)) {
System.out.println( "Couldn't rename file " + mFile
+ " to backup file " + mBackupFile);
mcr.setDiskWriteResult(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 (str == null) {
mcr.setDiskWriteResult(false);
return;
}
XmlUtils.writeMapXml(mcr.mapToWriteToDisk, str);
FileUtils.sync(str);
str.close();
setFilePermissionsFromMode(mFile.getPath(), mMode, 0);
if (mFile.canRead()) {
synchronized (this) {
mStatTimestamp = mFile.lastModified();
mStatSize = mFile.length();
}
}
// Writing was successful, delete the backup file if there is one.
mBackupFile.delete();
mcr.setDiskWriteResult(true);
return;
} catch (IOException e) {
System.out.println("writeToFile: Got exception:" + e);
}
// Clean up an unsuccessfully written file
if (mFile.exists()) {
if (!mFile.delete()) {
System.out.println("Couldn't clean up partially-written file " + mFile);
}
}
mcr.setDiskWriteResult(false);
}
static void setFilePermissionsFromMode(String name, int mode,
int extraPermissions) {
int perms = FileUtils.S_IRUSR|FileUtils.S_IWUSR
|FileUtils.S_IRGRP|FileUtils.S_IWGRP
|extraPermissions;
if ((mode&MODE_WORLD_READABLE) != 0) {
perms |= FileUtils.S_IROTH;
}
if ((mode&MODE_WORLD_WRITEABLE) != 0) {
perms |= FileUtils.S_IWOTH;
}
if (DEBUG) {
System.out.println("File " + name + ": mode=0x" + Integer.toHexString(mode)
+ ", perms=0x" + Integer.toHexString(perms));
}
// FileUtils.setPermissions(name, perms, -1, -1);
}
}