io.prestosql.jdbc.$internal.okhttp3.internal.cache.DiskLruCache Maven / Gradle / Ivy
/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.prestosql.jdbc.$internal.okhttp3.internal.cache;
import java.io.Closeable;
import java.io.EOFException;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.Flushable;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.NoSuchElementException;
import java.util.concurrent.Executor;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import io.prestosql.jdbc.$internal.javax.annotation.Nullable;
import io.prestosql.jdbc.$internal.okhttp3.internal.Util;
import io.prestosql.jdbc.$internal.okhttp3.internal.io.FileSystem;
import io.prestosql.jdbc.$internal.okhttp3.internal.platform.Platform;
import io.prestosql.jdbc.$internal.okio.BufferedSink;
import io.prestosql.jdbc.$internal.okio.BufferedSource;
import io.prestosql.jdbc.$internal.okio.Okio;
import io.prestosql.jdbc.$internal.okio.Sink;
import io.prestosql.jdbc.$internal.okio.Source;
import static io.prestosql.jdbc.$internal.okhttp3.internal.platform.Platform.WARN;
/**
* A cache that uses a bounded amount of space on a filesystem. Each cache entry has a string key
* and a fixed number of values. Each key must match the regex [a-z0-9_-]{1,64}.
* Values are byte sequences, accessible as streams or files. Each value must be between {@code 0}
* and {@code Integer.MAX_VALUE} bytes in length.
*
* The cache stores its data in a directory on the filesystem. This directory must be exclusive
* to the cache; the cache may delete or overwrite files from its directory. It is an error for
* multiple processes to use the same cache directory at the same time.
*
*
This cache limits the number of bytes that it will store on the filesystem. When the number of
* stored bytes exceeds the limit, the cache will remove entries in the background until the limit
* is satisfied. The limit is not strict: the cache may temporarily exceed it while waiting for
* files to be deleted. The limit does not include filesystem overhead or the cache journal so
* space-sensitive applications should set a conservative limit.
*
*
Clients call {@link #edit} to create or update the values of an entry. An entry may have only
* one editor at one time; if a value is not available to be edited then {@link #edit} will return
* null.
*
*
* - When an entry is being created it is necessary to supply a full set of
* values; the empty value should be used as a placeholder if necessary.
*
- When an entry is being edited, it is not necessary to supply data for
* every value; values default to their previous value.
*
*
* Every {@link #edit} call must be matched by a call to {@link Editor#commit} or {@link
* Editor#abort}. Committing is atomic: a read observes the full set of values as they were before
* or after the commit, but never a mix of values.
*
*
Clients call {@link #get} to read a snapshot of an entry. The read will observe the value at
* the time that {@link #get} was called. Updates and removals after the call do not impact ongoing
* reads.
*
*
This class is tolerant of some I/O errors. If files are missing from the filesystem, the
* corresponding entries will be dropped from the cache. If an error occurs while writing a cache
* value, the edit will fail silently. Callers should handle other problems by catching {@code
* IOException} and responding appropriately.
*/
public final class DiskLruCache implements Closeable, Flushable {
static final String JOURNAL_FILE = "journal";
static final String JOURNAL_FILE_TEMP = "journal.tmp";
static final String JOURNAL_FILE_BACKUP = "journal.bkp";
static final String MAGIC = "libcore.io.DiskLruCache";
static final String VERSION_1 = "1";
static final long ANY_SEQUENCE_NUMBER = -1;
static final Pattern LEGAL_KEY_PATTERN = Pattern.compile("[a-z0-9_-]{1,120}");
private static final String CLEAN = "CLEAN";
private static final String DIRTY = "DIRTY";
private static final String REMOVE = "REMOVE";
private static final String READ = "READ";
/*
* This cache uses a journal file named "journal". A typical journal file
* looks like this:
* libcore.io.DiskLruCache
* 1
* 100
* 2
*
* CLEAN 3400330d1dfc7f3f7f4b8d4d803dfcf6 832 21054
* DIRTY 335c4c6028171cfddfbaae1a9c313c52
* CLEAN 335c4c6028171cfddfbaae1a9c313c52 3934 2342
* REMOVE 335c4c6028171cfddfbaae1a9c313c52
* DIRTY 1ab96a171faeeee38496d8b330771a7a
* CLEAN 1ab96a171faeeee38496d8b330771a7a 1600 234
* READ 335c4c6028171cfddfbaae1a9c313c52
* READ 3400330d1dfc7f3f7f4b8d4d803dfcf6
*
* The first five lines of the journal form its header. They are the
* constant string "libcore.io.DiskLruCache", the disk cache's version,
* the application's version, the value count, and a blank line.
*
* Each of the subsequent lines in the file is a record of the state of a
* cache entry. Each line contains space-separated values: a state, a key,
* and optional state-specific values.
* o DIRTY lines track that an entry is actively being created or updated.
* Every successful DIRTY action should be followed by a CLEAN or REMOVE
* action. DIRTY lines without a matching CLEAN or REMOVE indicate that
* temporary files may need to be deleted.
* o CLEAN lines track a cache entry that has been successfully published
* and may be read. A publish line is followed by the lengths of each of
* its values.
* o READ lines track accesses for LRU.
* o REMOVE lines track entries that have been deleted.
*
* The journal file is appended to as cache operations occur. The journal may
* occasionally be compacted by dropping redundant lines. A temporary file named
* "journal.tmp" will be used during compaction; that file should be deleted if
* it exists when the cache is opened.
*/
final FileSystem fileSystem;
final File directory;
private final File journalFile;
private final File journalFileTmp;
private final File journalFileBackup;
private final int appVersion;
private long maxSize;
final int valueCount;
private long size = 0;
BufferedSink journalWriter;
final LinkedHashMap lruEntries = new LinkedHashMap<>(0, 0.75f, true);
int redundantOpCount;
boolean hasJournalErrors;
// Must be read and written when synchronized on 'this'.
boolean initialized;
boolean closed;
boolean mostRecentTrimFailed;
boolean mostRecentRebuildFailed;
/**
* To differentiate between old and current snapshots, each entry is given a sequence number each
* time an edit is committed. A snapshot is stale if its sequence number is not equal to its
* entry's sequence number.
*/
private long nextSequenceNumber = 0;
/** Used to run 'cleanupRunnable' for journal rebuilds. */
private final Executor executor;
private final Runnable cleanupRunnable = new Runnable() {
public void run() {
synchronized (DiskLruCache.this) {
if (!initialized | closed) {
return; // Nothing to do
}
try {
trimToSize();
} catch (IOException ignored) {
mostRecentTrimFailed = true;
}
try {
if (journalRebuildRequired()) {
rebuildJournal();
redundantOpCount = 0;
}
} catch (IOException e) {
mostRecentRebuildFailed = true;
journalWriter = Okio.buffer(Okio.blackhole());
}
}
}
};
DiskLruCache(FileSystem fileSystem, File directory, int appVersion, int valueCount, long maxSize,
Executor executor) {
this.fileSystem = fileSystem;
this.directory = directory;
this.appVersion = appVersion;
this.journalFile = new File(directory, JOURNAL_FILE);
this.journalFileTmp = new File(directory, JOURNAL_FILE_TEMP);
this.journalFileBackup = new File(directory, JOURNAL_FILE_BACKUP);
this.valueCount = valueCount;
this.maxSize = maxSize;
this.executor = executor;
}
public synchronized void initialize() throws IOException {
assert Thread.holdsLock(this);
if (initialized) {
return; // Already initialized.
}
// If a bkp file exists, use it instead.
if (fileSystem.exists(journalFileBackup)) {
// If journal file also exists just delete backup file.
if (fileSystem.exists(journalFile)) {
fileSystem.delete(journalFileBackup);
} else {
fileSystem.rename(journalFileBackup, journalFile);
}
}
// Prefer to pick up where we left off.
if (fileSystem.exists(journalFile)) {
try {
readJournal();
processJournal();
initialized = true;
return;
} catch (IOException journalIsCorrupt) {
Platform.get().log(WARN, "DiskLruCache " + directory + " is corrupt: "
+ journalIsCorrupt.getMessage() + ", removing", journalIsCorrupt);
}
// The cache is corrupted, attempt to delete the contents of the directory. This can throw and
// we'll let that propagate out as it likely means there is a severe filesystem problem.
try {
delete();
} finally {
closed = false;
}
}
rebuildJournal();
initialized = true;
}
/**
* Create a cache which will reside in {@code directory}. This cache is lazily initialized on
* first access and will be created if it does not exist.
*
* @param directory a writable directory
* @param valueCount the number of values per cache entry. Must be positive.
* @param maxSize the maximum number of bytes this cache should use to store
*/
public static DiskLruCache create(FileSystem fileSystem, File directory, int appVersion,
int valueCount, long maxSize) {
if (maxSize <= 0) {
throw new IllegalArgumentException("maxSize <= 0");
}
if (valueCount <= 0) {
throw new IllegalArgumentException("valueCount <= 0");
}
// Use a single background thread to evict entries.
Executor executor = new ThreadPoolExecutor(0, 1, 60L, TimeUnit.SECONDS,
new LinkedBlockingQueue(), Util.threadFactory("OkHttp DiskLruCache", true));
return new DiskLruCache(fileSystem, directory, appVersion, valueCount, maxSize, executor);
}
private void readJournal() throws IOException {
BufferedSource source = Okio.buffer(fileSystem.source(journalFile));
try {
String magic = source.readUtf8LineStrict();
String version = source.readUtf8LineStrict();
String appVersionString = source.readUtf8LineStrict();
String valueCountString = source.readUtf8LineStrict();
String blank = source.readUtf8LineStrict();
if (!MAGIC.equals(magic)
|| !VERSION_1.equals(version)
|| !Integer.toString(appVersion).equals(appVersionString)
|| !Integer.toString(valueCount).equals(valueCountString)
|| !"".equals(blank)) {
throw new IOException("unexpected journal header: [" + magic + ", " + version + ", "
+ valueCountString + ", " + blank + "]");
}
int lineCount = 0;
while (true) {
try {
readJournalLine(source.readUtf8LineStrict());
lineCount++;
} catch (EOFException endOfJournal) {
break;
}
}
redundantOpCount = lineCount - lruEntries.size();
// If we ended on a truncated line, rebuild the journal before appending to it.
if (!source.exhausted()) {
rebuildJournal();
} else {
journalWriter = newJournalWriter();
}
} finally {
Util.closeQuietly(source);
}
}
private BufferedSink newJournalWriter() throws FileNotFoundException {
Sink fileSink = fileSystem.appendingSink(journalFile);
Sink faultHidingSink = new FaultHidingSink(fileSink) {
@Override protected void onException(IOException e) {
assert (Thread.holdsLock(DiskLruCache.this));
hasJournalErrors = true;
}
};
return Okio.buffer(faultHidingSink);
}
private void readJournalLine(String line) throws IOException {
int firstSpace = line.indexOf(' ');
if (firstSpace == -1) {
throw new IOException("unexpected journal line: " + line);
}
int keyBegin = firstSpace + 1;
int secondSpace = line.indexOf(' ', keyBegin);
final String key;
if (secondSpace == -1) {
key = line.substring(keyBegin);
if (firstSpace == REMOVE.length() && line.startsWith(REMOVE)) {
lruEntries.remove(key);
return;
}
} else {
key = line.substring(keyBegin, secondSpace);
}
Entry entry = lruEntries.get(key);
if (entry == null) {
entry = new Entry(key);
lruEntries.put(key, entry);
}
if (secondSpace != -1 && firstSpace == CLEAN.length() && line.startsWith(CLEAN)) {
String[] parts = line.substring(secondSpace + 1).split(" ");
entry.readable = true;
entry.currentEditor = null;
entry.setLengths(parts);
} else if (secondSpace == -1 && firstSpace == DIRTY.length() && line.startsWith(DIRTY)) {
entry.currentEditor = new Editor(entry);
} else if (secondSpace == -1 && firstSpace == READ.length() && line.startsWith(READ)) {
// This work was already done by calling lruEntries.get().
} else {
throw new IOException("unexpected journal line: " + line);
}
}
/**
* Computes the initial size and collects garbage as a part of opening the cache. Dirty entries
* are assumed to be inconsistent and will be deleted.
*/
private void processJournal() throws IOException {
fileSystem.delete(journalFileTmp);
for (Iterator i = lruEntries.values().iterator(); i.hasNext(); ) {
Entry entry = i.next();
if (entry.currentEditor == null) {
for (int t = 0; t < valueCount; t++) {
size += entry.lengths[t];
}
} else {
entry.currentEditor = null;
for (int t = 0; t < valueCount; t++) {
fileSystem.delete(entry.cleanFiles[t]);
fileSystem.delete(entry.dirtyFiles[t]);
}
i.remove();
}
}
}
/**
* Creates a new journal that omits redundant information. This replaces the current journal if it
* exists.
*/
synchronized void rebuildJournal() throws IOException {
if (journalWriter != null) {
journalWriter.close();
}
BufferedSink writer = Okio.buffer(fileSystem.sink(journalFileTmp));
try {
writer.writeUtf8(MAGIC).writeByte('\n');
writer.writeUtf8(VERSION_1).writeByte('\n');
writer.writeDecimalLong(appVersion).writeByte('\n');
writer.writeDecimalLong(valueCount).writeByte('\n');
writer.writeByte('\n');
for (Entry entry : lruEntries.values()) {
if (entry.currentEditor != null) {
writer.writeUtf8(DIRTY).writeByte(' ');
writer.writeUtf8(entry.key);
writer.writeByte('\n');
} else {
writer.writeUtf8(CLEAN).writeByte(' ');
writer.writeUtf8(entry.key);
entry.writeLengths(writer);
writer.writeByte('\n');
}
}
} finally {
writer.close();
}
if (fileSystem.exists(journalFile)) {
fileSystem.rename(journalFile, journalFileBackup);
}
fileSystem.rename(journalFileTmp, journalFile);
fileSystem.delete(journalFileBackup);
journalWriter = newJournalWriter();
hasJournalErrors = false;
mostRecentRebuildFailed = false;
}
/**
* Returns a snapshot of the entry named {@code key}, or null if it doesn't exist is not currently
* readable. If a value is returned, it is moved to the head of the LRU queue.
*/
public synchronized Snapshot get(String key) throws IOException {
initialize();
checkNotClosed();
validateKey(key);
Entry entry = lruEntries.get(key);
if (entry == null || !entry.readable) return null;
Snapshot snapshot = entry.snapshot();
if (snapshot == null) return null;
redundantOpCount++;
journalWriter.writeUtf8(READ).writeByte(' ').writeUtf8(key).writeByte('\n');
if (journalRebuildRequired()) {
executor.execute(cleanupRunnable);
}
return snapshot;
}
/**
* Returns an editor for the entry named {@code key}, or null if another edit is in progress.
*/
public @Nullable Editor edit(String key) throws IOException {
return edit(key, ANY_SEQUENCE_NUMBER);
}
synchronized Editor edit(String key, long expectedSequenceNumber) throws IOException {
initialize();
checkNotClosed();
validateKey(key);
Entry entry = lruEntries.get(key);
if (expectedSequenceNumber != ANY_SEQUENCE_NUMBER && (entry == null
|| entry.sequenceNumber != expectedSequenceNumber)) {
return null; // Snapshot is stale.
}
if (entry != null && entry.currentEditor != null) {
return null; // Another edit is in progress.
}
if (mostRecentTrimFailed || mostRecentRebuildFailed) {
// The OS has become our enemy! If the trim job failed, it means we are storing more data than
// requested by the user. Do not allow edits so we do not go over that limit any further. If
// the journal rebuild failed, the journal writer will not be active, meaning we will not be
// able to record the edit, causing file leaks. In both cases, we want to retry the clean up
// so we can get out of this state!
executor.execute(cleanupRunnable);
return null;
}
// Flush the journal before creating files to prevent file leaks.
journalWriter.writeUtf8(DIRTY).writeByte(' ').writeUtf8(key).writeByte('\n');
journalWriter.flush();
if (hasJournalErrors) {
return null; // Don't edit; the journal can't be written.
}
if (entry == null) {
entry = new Entry(key);
lruEntries.put(key, entry);
}
Editor editor = new Editor(entry);
entry.currentEditor = editor;
return editor;
}
/** Returns the directory where this cache stores its data. */
public File getDirectory() {
return directory;
}
/**
* Returns the maximum number of bytes that this cache should use to store its data.
*/
public synchronized long getMaxSize() {
return maxSize;
}
/**
* Changes the maximum number of bytes the cache can store and queues a job to trim the existing
* store, if necessary.
*/
public synchronized void setMaxSize(long maxSize) {
this.maxSize = maxSize;
if (initialized) {
executor.execute(cleanupRunnable);
}
}
/**
* Returns the number of bytes currently being used to store the values in this cache. This may be
* greater than the max size if a background deletion is pending.
*/
public synchronized long size() throws IOException {
initialize();
return size;
}
synchronized void completeEdit(Editor editor, boolean success) throws IOException {
Entry entry = editor.entry;
if (entry.currentEditor != editor) {
throw new IllegalStateException();
}
// If this edit is creating the entry for the first time, every index must have a value.
if (success && !entry.readable) {
for (int i = 0; i < valueCount; i++) {
if (!editor.written[i]) {
editor.abort();
throw new IllegalStateException("Newly created entry didn't create value for index " + i);
}
if (!fileSystem.exists(entry.dirtyFiles[i])) {
editor.abort();
return;
}
}
}
for (int i = 0; i < valueCount; i++) {
File dirty = entry.dirtyFiles[i];
if (success) {
if (fileSystem.exists(dirty)) {
File clean = entry.cleanFiles[i];
fileSystem.rename(dirty, clean);
long oldLength = entry.lengths[i];
long newLength = fileSystem.size(clean);
entry.lengths[i] = newLength;
size = size - oldLength + newLength;
}
} else {
fileSystem.delete(dirty);
}
}
redundantOpCount++;
entry.currentEditor = null;
if (entry.readable | success) {
entry.readable = true;
journalWriter.writeUtf8(CLEAN).writeByte(' ');
journalWriter.writeUtf8(entry.key);
entry.writeLengths(journalWriter);
journalWriter.writeByte('\n');
if (success) {
entry.sequenceNumber = nextSequenceNumber++;
}
} else {
lruEntries.remove(entry.key);
journalWriter.writeUtf8(REMOVE).writeByte(' ');
journalWriter.writeUtf8(entry.key);
journalWriter.writeByte('\n');
}
journalWriter.flush();
if (size > maxSize || journalRebuildRequired()) {
executor.execute(cleanupRunnable);
}
}
/**
* We only rebuild the journal when it will halve the size of the journal and eliminate at least
* 2000 ops.
*/
boolean journalRebuildRequired() {
final int redundantOpCompactThreshold = 2000;
return redundantOpCount >= redundantOpCompactThreshold
&& redundantOpCount >= lruEntries.size();
}
/**
* Drops the entry for {@code key} if it exists and can be removed. If the entry for {@code key}
* is currently being edited, that edit will complete normally but its value will not be stored.
*
* @return true if an entry was removed.
*/
public synchronized boolean remove(String key) throws IOException {
initialize();
checkNotClosed();
validateKey(key);
Entry entry = lruEntries.get(key);
if (entry == null) return false;
boolean removed = removeEntry(entry);
if (removed && size <= maxSize) mostRecentTrimFailed = false;
return removed;
}
boolean removeEntry(Entry entry) throws IOException {
if (entry.currentEditor != null) {
entry.currentEditor.detach(); // Prevent the edit from completing normally.
}
for (int i = 0; i < valueCount; i++) {
fileSystem.delete(entry.cleanFiles[i]);
size -= entry.lengths[i];
entry.lengths[i] = 0;
}
redundantOpCount++;
journalWriter.writeUtf8(REMOVE).writeByte(' ').writeUtf8(entry.key).writeByte('\n');
lruEntries.remove(entry.key);
if (journalRebuildRequired()) {
executor.execute(cleanupRunnable);
}
return true;
}
/** Returns true if this cache has been closed. */
public synchronized boolean isClosed() {
return closed;
}
private synchronized void checkNotClosed() {
if (isClosed()) {
throw new IllegalStateException("cache is closed");
}
}
/** Force buffered operations to the filesystem. */
@Override public synchronized void flush() throws IOException {
if (!initialized) return;
checkNotClosed();
trimToSize();
journalWriter.flush();
}
/** Closes this cache. Stored values will remain on the filesystem. */
@Override public synchronized void close() throws IOException {
if (!initialized || closed) {
closed = true;
return;
}
// Copying for safe iteration.
for (Entry entry : lruEntries.values().toArray(new Entry[lruEntries.size()])) {
if (entry.currentEditor != null) {
entry.currentEditor.abort();
}
}
trimToSize();
journalWriter.close();
journalWriter = null;
closed = true;
}
void trimToSize() throws IOException {
while (size > maxSize) {
Entry toEvict = lruEntries.values().iterator().next();
removeEntry(toEvict);
}
mostRecentTrimFailed = false;
}
/**
* Closes the cache and deletes all of its stored values. This will delete all files in the cache
* directory including files that weren't created by the cache.
*/
public void delete() throws IOException {
close();
fileSystem.deleteContents(directory);
}
/**
* Deletes all stored values from the cache. In-flight edits will complete normally but their
* values will not be stored.
*/
public synchronized void evictAll() throws IOException {
initialize();
// Copying for safe iteration.
for (Entry entry : lruEntries.values().toArray(new Entry[lruEntries.size()])) {
removeEntry(entry);
}
mostRecentTrimFailed = false;
}
private void validateKey(String key) {
Matcher matcher = LEGAL_KEY_PATTERN.matcher(key);
if (!matcher.matches()) {
throw new IllegalArgumentException(
"keys must match regex [a-z0-9_-]{1,120}: \"" + key + "\"");
}
}
/**
* Returns an iterator over the cache's current entries. This iterator doesn't throw {@code
* ConcurrentModificationException}, but if new entries are added while iterating, those new
* entries will not be returned by the iterator. If existing entries are removed during iteration,
* they will be absent (unless they were already returned).
*
* If there are I/O problems during iteration, this iterator fails silently. For example, if
* the hosting filesystem becomes unreachable, the iterator will omit elements rather than
* throwing exceptions.
*
*
The caller must {@link Snapshot#close close} each snapshot returned by
* {@link Iterator#next}. Failing to do so leaks open files!
*
*
The returned iterator supports {@link Iterator#remove}.
*/
public synchronized Iterator snapshots() throws IOException {
initialize();
return new Iterator() {
/** Iterate a copy of the entries to defend against concurrent modification errors. */
final Iterator delegate = new ArrayList<>(lruEntries.values()).iterator();
/** The snapshot to return from {@link #next}. Null if we haven't computed that yet. */
Snapshot nextSnapshot;
/** The snapshot to remove with {@link #remove}. Null if removal is illegal. */
Snapshot removeSnapshot;
@Override public boolean hasNext() {
if (nextSnapshot != null) return true;
synchronized (DiskLruCache.this) {
// If the cache is closed, truncate the iterator.
if (closed) return false;
while (delegate.hasNext()) {
Entry entry = delegate.next();
Snapshot snapshot = entry.snapshot();
if (snapshot == null) continue; // Evicted since we copied the entries.
nextSnapshot = snapshot;
return true;
}
}
return false;
}
@Override public Snapshot next() {
if (!hasNext()) throw new NoSuchElementException();
removeSnapshot = nextSnapshot;
nextSnapshot = null;
return removeSnapshot;
}
@Override public void remove() {
if (removeSnapshot == null) throw new IllegalStateException("remove() before next()");
try {
DiskLruCache.this.remove(removeSnapshot.key);
} catch (IOException ignored) {
// Nothing useful to do here. We failed to remove from the cache. Most likely that's
// because we couldn't update the journal, but the cached entry will still be gone.
} finally {
removeSnapshot = null;
}
}
};
}
/** A snapshot of the values for an entry. */
public final class Snapshot implements Closeable {
private final String key;
private final long sequenceNumber;
private final Source[] sources;
private final long[] lengths;
Snapshot(String key, long sequenceNumber, Source[] sources, long[] lengths) {
this.key = key;
this.sequenceNumber = sequenceNumber;
this.sources = sources;
this.lengths = lengths;
}
public String key() {
return key;
}
/**
* Returns an editor for this snapshot's entry, or null if either the entry has changed since
* this snapshot was created or if another edit is in progress.
*/
public @Nullable Editor edit() throws IOException {
return DiskLruCache.this.edit(key, sequenceNumber);
}
/** Returns the unbuffered stream with the value for {@code index}. */
public Source getSource(int index) {
return sources[index];
}
/** Returns the byte length of the value for {@code index}. */
public long getLength(int index) {
return lengths[index];
}
public void close() {
for (Source in : sources) {
Util.closeQuietly(in);
}
}
}
/** Edits the values for an entry. */
public final class Editor {
final Entry entry;
final boolean[] written;
private boolean done;
Editor(Entry entry) {
this.entry = entry;
this.written = (entry.readable) ? null : new boolean[valueCount];
}
/**
* Prevents this editor from completing normally. This is necessary either when the edit causes
* an I/O error, or if the target entry is evicted while this editor is active. In either case
* we delete the editor's created files and prevent new files from being created. Note that once
* an editor has been detached it is possible for another editor to edit the entry.
*/
void detach() {
if (entry.currentEditor == this) {
for (int i = 0; i < valueCount; i++) {
try {
fileSystem.delete(entry.dirtyFiles[i]);
} catch (IOException e) {
// This file is potentially leaked. Not much we can do about that.
}
}
entry.currentEditor = null;
}
}
/**
* Returns an unbuffered input stream to read the last committed value, or null if no value has
* been committed.
*/
public Source newSource(int index) {
synchronized (DiskLruCache.this) {
if (done) {
throw new IllegalStateException();
}
if (!entry.readable || entry.currentEditor != this) {
return null;
}
try {
return fileSystem.source(entry.cleanFiles[index]);
} catch (FileNotFoundException e) {
return null;
}
}
}
/**
* Returns a new unbuffered output stream to write the value at {@code index}. If the underlying
* output stream encounters errors when writing to the filesystem, this edit will be aborted
* when {@link #commit} is called. The returned output stream does not throw IOExceptions.
*/
public Sink newSink(int index) {
synchronized (DiskLruCache.this) {
if (done) {
throw new IllegalStateException();
}
if (entry.currentEditor != this) {
return Okio.blackhole();
}
if (!entry.readable) {
written[index] = true;
}
File dirtyFile = entry.dirtyFiles[index];
Sink sink;
try {
sink = fileSystem.sink(dirtyFile);
} catch (FileNotFoundException e) {
return Okio.blackhole();
}
return new FaultHidingSink(sink) {
@Override protected void onException(IOException e) {
synchronized (DiskLruCache.this) {
detach();
}
}
};
}
}
/**
* Commits this edit so it is visible to readers. This releases the edit lock so another edit
* may be started on the same key.
*/
public void commit() throws IOException {
synchronized (DiskLruCache.this) {
if (done) {
throw new IllegalStateException();
}
if (entry.currentEditor == this) {
completeEdit(this, true);
}
done = true;
}
}
/**
* Aborts this edit. This releases the edit lock so another edit may be started on the same
* key.
*/
public void abort() throws IOException {
synchronized (DiskLruCache.this) {
if (done) {
throw new IllegalStateException();
}
if (entry.currentEditor == this) {
completeEdit(this, false);
}
done = true;
}
}
public void abortUnlessCommitted() {
synchronized (DiskLruCache.this) {
if (!done && entry.currentEditor == this) {
try {
completeEdit(this, false);
} catch (IOException ignored) {
}
}
}
}
}
private final class Entry {
final String key;
/** Lengths of this entry's files. */
final long[] lengths;
final File[] cleanFiles;
final File[] dirtyFiles;
/** True if this entry has ever been published. */
boolean readable;
/** The ongoing edit or null if this entry is not being edited. */
Editor currentEditor;
/** The sequence number of the most recently committed edit to this entry. */
long sequenceNumber;
Entry(String key) {
this.key = key;
lengths = new long[valueCount];
cleanFiles = new File[valueCount];
dirtyFiles = new File[valueCount];
// The names are repetitive so re-use the same builder to avoid allocations.
StringBuilder fileBuilder = new StringBuilder(key).append('.');
int truncateTo = fileBuilder.length();
for (int i = 0; i < valueCount; i++) {
fileBuilder.append(i);
cleanFiles[i] = new File(directory, fileBuilder.toString());
fileBuilder.append(".tmp");
dirtyFiles[i] = new File(directory, fileBuilder.toString());
fileBuilder.setLength(truncateTo);
}
}
/** Set lengths using decimal numbers like "10123". */
void setLengths(String[] strings) throws IOException {
if (strings.length != valueCount) {
throw invalidLengths(strings);
}
try {
for (int i = 0; i < strings.length; i++) {
lengths[i] = Long.parseLong(strings[i]);
}
} catch (NumberFormatException e) {
throw invalidLengths(strings);
}
}
/** Append space-prefixed lengths to {@code writer}. */
void writeLengths(BufferedSink writer) throws IOException {
for (long length : lengths) {
writer.writeByte(' ').writeDecimalLong(length);
}
}
private IOException invalidLengths(String[] strings) throws IOException {
throw new IOException("unexpected journal line: " + Arrays.toString(strings));
}
/**
* Returns a snapshot of this entry. This opens all streams eagerly to guarantee that we see a
* single published snapshot. If we opened streams lazily then the streams could come from
* different edits.
*/
Snapshot snapshot() {
if (!Thread.holdsLock(DiskLruCache.this)) throw new AssertionError();
Source[] sources = new Source[valueCount];
long[] lengths = this.lengths.clone(); // Defensive copy since these can be zeroed out.
try {
for (int i = 0; i < valueCount; i++) {
sources[i] = fileSystem.source(cleanFiles[i]);
}
return new Snapshot(key, sequenceNumber, sources, lengths);
} catch (FileNotFoundException e) {
// A file must have been deleted manually!
for (int i = 0; i < valueCount; i++) {
if (sources[i] != null) {
Util.closeQuietly(sources[i]);
} else {
break;
}
}
// Since the entry is no longer valid, remove it so the metadata is accurate (i.e. the cache
// size.)
try {
removeEntry(this);
} catch (IOException ignored) {
}
return null;
}
}
}
}