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+/*
+ * 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 com.jakewharton.disklrucache;
+
+import java.io.BufferedWriter;
+import java.io.Closeable;
+import java.io.EOFException;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.FilterOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.concurrent.Callable;
+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;
+
+/**
+ * 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 <strong>[a-z0-9_-]{1,120}</strong>. Values are byte sequences,
+ * accessible as streams or files. Each value must be between {@code 0} and
+ * {@code Integer.MAX_VALUE} bytes in length.
+ *
+ * <p>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.
+ *
+ * <p>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.
+ *
+ * <p>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.
+ * <ul>
+ * <li>When an entry is being <strong>created</strong> it is necessary to
+ * supply a full set of values; the empty value should be used as a
+ * placeholder if necessary.
+ * <li>When an entry is being <strong>edited</strong>, it is not necessary
+ * to supply data for every value; values default to their previous
+ * value.
+ * </ul>
+ * 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.
+ *
+ * <p>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.
+ *
+ * <p>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 {
+ 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 String STRING_KEY_PATTERN = "[a-z0-9_-]{1,120}";
+ static final Pattern LEGAL_KEY_PATTERN = Pattern.compile(STRING_KEY_PATTERN);
+ 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.
+ */
+
+ private final File directory;
+ private final File journalFile;
+ private final File journalFileTmp;
+ private final File journalFileBackup;
+ private final int appVersion;
+ private long maxSize;
+ private final int valueCount;
+ private long size = 0;
+ private Writer journalWriter;
+ private final LinkedHashMap<String, Entry> lruEntries =
+ new LinkedHashMap<String, Entry>(0, 0.75f, true);
+ private int redundantOpCount;
+
+ /**
+ * 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;
+
+ /** This cache uses a single background thread to evict entries. */
+ final ThreadPoolExecutor executorService =
+ new ThreadPoolExecutor(0, 1, 60L, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());
+ private final Callable<Void> cleanupCallable = new Callable<Void>() {
+ public Void call() throws Exception {
+ synchronized (DiskLruCache.this) {
+ if (journalWriter == null) {
+ return null; // Closed.
+ }
+ trimToSize();
+ if (journalRebuildRequired()) {
+ rebuildJournal();
+ redundantOpCount = 0;
+ }
+ }
+ return null;
+ }
+ };
+
+ private DiskLruCache(File directory, int appVersion, int valueCount, long maxSize) {
+ 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;
+ }
+
+ /**
+ * Opens the cache in {@code directory}, creating a cache if none exists
+ * there.
+ *
+ * @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
+ * @throws IOException if reading or writing the cache directory fails
+ */
+ public static DiskLruCache open(File directory, int appVersion, int valueCount, long maxSize)
+ throws IOException {
+ if (maxSize <= 0) {
+ throw new IllegalArgumentException("maxSize <= 0");
+ }
+ if (valueCount <= 0) {
+ throw new IllegalArgumentException("valueCount <= 0");
+ }
+
+ // If a bkp file exists, use it instead.
+ File backupFile = new File(directory, JOURNAL_FILE_BACKUP);
+ if (backupFile.exists()) {
+ File journalFile = new File(directory, JOURNAL_FILE);
+ // If journal file also exists just delete backup file.
+ if (journalFile.exists()) {
+ backupFile.delete();
+ } else {
+ renameTo(backupFile, journalFile, false);
+ }
+ }
+
+ // Prefer to pick up where we left off.
+ DiskLruCache cache = new DiskLruCache(directory, appVersion, valueCount, maxSize);
+ if (cache.journalFile.exists()) {
+ try {
+ cache.readJournal();
+ cache.processJournal();
+ return cache;
+ } catch (IOException journalIsCorrupt) {
+ System.out
+ .println("DiskLruCache "
+ + directory
+ + " is corrupt: "
+ + journalIsCorrupt.getMessage()
+ + ", removing");
+ cache.delete();
+ }
+ }
+
+ // Create a new empty cache.
+ directory.mkdirs();
+ cache = new DiskLruCache(directory, appVersion, valueCount, maxSize);
+ cache.rebuildJournal();
+ return cache;
+ }
+
+ private void readJournal() throws IOException {
+ StrictLineReader reader = new StrictLineReader(new FileInputStream(journalFile), Util.US_ASCII);
+ try {
+ String magic = reader.readLine();
+ String version = reader.readLine();
+ String appVersionString = reader.readLine();
+ String valueCountString = reader.readLine();
+ String blank = reader.readLine();
+ 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(reader.readLine());
+ lineCount++;
+ } catch (EOFException endOfJournal) {
+ break;
+ }
+ }
+ redundantOpCount = lineCount - lruEntries.size();
+
+ // If we ended on a truncated line, rebuild the journal before appending to it.
+ if (reader.hasUnterminatedLine()) {
+ rebuildJournal();
+ } else {
+ journalWriter = new BufferedWriter(new OutputStreamWriter(
+ new FileOutputStream(journalFile, true), Util.US_ASCII));
+ }
+ } finally {
+ Util.closeQuietly(reader);
+ }
+ }
+
+ 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 {
+ deleteIfExists(journalFileTmp);
+ for (Iterator<Entry> 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++) {
+ deleteIfExists(entry.getCleanFile(t));
+ deleteIfExists(entry.getDirtyFile(t));
+ }
+ i.remove();
+ }
+ }
+ }
+
+ /**
+ * Creates a new journal that omits redundant information. This replaces the
+ * current journal if it exists.
+ */
+ private synchronized void rebuildJournal() throws IOException {
+ if (journalWriter != null) {
+ journalWriter.close();
+ }
+
+ Writer writer = new BufferedWriter(
+ new OutputStreamWriter(new FileOutputStream(journalFileTmp), Util.US_ASCII));
+ try {
+ writer.write(MAGIC);
+ writer.write("\n");
+ writer.write(VERSION_1);
+ writer.write("\n");
+ writer.write(Integer.toString(appVersion));
+ writer.write("\n");
+ writer.write(Integer.toString(valueCount));
+ writer.write("\n");
+ writer.write("\n");
+
+ for (Entry entry : lruEntries.values()) {
+ if (entry.currentEditor != null) {
+ writer.write(DIRTY + ' ' + entry.key + '\n');
+ } else {
+ writer.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n');
+ }
+ }
+ } finally {
+ writer.close();
+ }
+
+ if (journalFile.exists()) {
+ renameTo(journalFile, journalFileBackup, true);
+ }
+ renameTo(journalFileTmp, journalFile, false);
+ journalFileBackup.delete();
+
+ journalWriter = new BufferedWriter(
+ new OutputStreamWriter(new FileOutputStream(journalFile, true), Util.US_ASCII));
+ }
+
+ private static void deleteIfExists(File file) throws IOException {
+ if (file.exists() && !file.delete()) {
+ throw new IOException();
+ }
+ }
+
+ private static void renameTo(File from, File to, boolean deleteDestination) throws IOException {
+ if (deleteDestination) {
+ deleteIfExists(to);
+ }
+ if (!from.renameTo(to)) {
+ throw new IOException();
+ }
+ }
+
+ /**
+ * 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 {
+ checkNotClosed();
+ validateKey(key);
+ Entry entry = lruEntries.get(key);
+ if (entry == null) {
+ return null;
+ }
+
+ if (!entry.readable) {
+ return null;
+ }
+
+ // Open 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.
+ InputStream[] ins = new InputStream[valueCount];
+ try {
+ for (int i = 0; i < valueCount; i++) {
+ ins[i] = new FileInputStream(entry.getCleanFile(i));
+ }
+ } catch (FileNotFoundException e) {
+ // A file must have been deleted manually!
+ for (int i = 0; i < valueCount; i++) {
+ if (ins[i] != null) {
+ Util.closeQuietly(ins[i]);
+ } else {
+ break;
+ }
+ }
+ return null;
+ }
+
+ redundantOpCount++;
+ journalWriter.append(READ + ' ' + key + '\n');
+ if (journalRebuildRequired()) {
+ executorService.submit(cleanupCallable);
+ }
+
+ return new Snapshot(key, entry.sequenceNumber, ins, entry.lengths);
+ }
+
+ /**
+ * Returns an editor for the entry named {@code key}, or null if another
+ * edit is in progress.
+ */
+ public Editor edit(String key) throws IOException {
+ return edit(key, ANY_SEQUENCE_NUMBER);
+ }
+
+ private synchronized Editor edit(String key, long expectedSequenceNumber) throws IOException {
+ 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 = new Entry(key);
+ lruEntries.put(key, entry);
+ } else if (entry.currentEditor != null) {
+ return null; // Another edit is in progress.
+ }
+
+ Editor editor = new Editor(entry);
+ entry.currentEditor = editor;
+
+ // Flush the journal before creating files to prevent file leaks.
+ journalWriter.write(DIRTY + ' ' + key + '\n');
+ journalWriter.flush();
+ 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;
+ executorService.submit(cleanupCallable);
+ }
+
+ /**
+ * 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() {
+ return size;
+ }
+
+ private 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 (!entry.getDirtyFile(i).exists()) {
+ editor.abort();
+ return;
+ }
+ }
+ }
+
+ for (int i = 0; i < valueCount; i++) {
+ File dirty = entry.getDirtyFile(i);
+ if (success) {
+ if (dirty.exists()) {
+ File clean = entry.getCleanFile(i);
+ dirty.renameTo(clean);
+ long oldLength = entry.lengths[i];
+ long newLength = clean.length();
+ entry.lengths[i] = newLength;
+ size = size - oldLength + newLength;
+ }
+ } else {
+ deleteIfExists(dirty);
+ }
+ }
+
+ redundantOpCount++;
+ entry.currentEditor = null;
+ if (entry.readable | success) {
+ entry.readable = true;
+ journalWriter.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n');
+ if (success) {
+ entry.sequenceNumber = nextSequenceNumber++;
+ }
+ } else {
+ lruEntries.remove(entry.key);
+ journalWriter.write(REMOVE + ' ' + entry.key + '\n');
+ }
+ journalWriter.flush();
+
+ if (size > maxSize || journalRebuildRequired()) {
+ executorService.submit(cleanupCallable);
+ }
+ }
+
+ /**
+ * We only rebuild the journal when it will halve the size of the journal
+ * and eliminate at least 2000 ops.
+ */
+ private 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. Entries
+ * actively being edited cannot be removed.
+ *
+ * @return true if an entry was removed.
+ */
+ public synchronized boolean remove(String key) throws IOException {
+ checkNotClosed();
+ validateKey(key);
+ Entry entry = lruEntries.get(key);
+ if (entry == null || entry.currentEditor != null) {
+ return false;
+ }
+
+ for (int i = 0; i < valueCount; i++) {
+ File file = entry.getCleanFile(i);
+ if (file.exists() && !file.delete()) {
+ throw new IOException("failed to delete " + file);
+ }
+ size -= entry.lengths[i];
+ entry.lengths[i] = 0;
+ }
+
+ redundantOpCount++;
+ journalWriter.append(REMOVE + ' ' + key + '\n');
+ lruEntries.remove(key);
+
+ if (journalRebuildRequired()) {
+ executorService.submit(cleanupCallable);
+ }
+
+ return true;
+ }
+
+ /** Returns true if this cache has been closed. */
+ public synchronized boolean isClosed() {
+ return journalWriter == null;
+ }
+
+ private void checkNotClosed() {
+ if (journalWriter == null) {
+ throw new IllegalStateException("cache is closed");
+ }
+ }
+
+ /** Force buffered operations to the filesystem. */
+ public synchronized void flush() throws IOException {
+ checkNotClosed();
+ trimToSize();
+ journalWriter.flush();
+ }
+
+ /** Closes this cache. Stored values will remain on the filesystem. */
+ public synchronized void close() throws IOException {
+ if (journalWriter == null) {
+ return; // Already closed.
+ }
+ for (Entry entry : new ArrayList<Entry>(lruEntries.values())) {
+ if (entry.currentEditor != null) {
+ entry.currentEditor.abort();
+ }
+ }
+ trimToSize();
+ journalWriter.close();
+ journalWriter = null;
+ }
+
+ private void trimToSize() throws IOException {
+ while (size > maxSize) {
+ Map.Entry<String, Entry> toEvict = lruEntries.entrySet().iterator().next();
+ remove(toEvict.getKey());
+ }
+ }
+
+ /**
+ * 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();
+ Util.deleteContents(directory);
+ }
+
+ private void validateKey(String key) {
+ Matcher matcher = LEGAL_KEY_PATTERN.matcher(key);
+ if (!matcher.matches()) {
+ throw new IllegalArgumentException("keys must match regex "
+ + STRING_KEY_PATTERN + ": \"" + key + "\"");
+ }
+ }
+
+ private static String inputStreamToString(InputStream in) throws IOException {
+ return Util.readFully(new InputStreamReader(in, Util.UTF_8));
+ }
+
+ /** A snapshot of the values for an entry. */
+ public final class Snapshot implements Closeable {
+ private final String key;
+ private final long sequenceNumber;
+ private final InputStream[] ins;
+ private final long[] lengths;
+
+ private Snapshot(String key, long sequenceNumber, InputStream[] ins, long[] lengths) {
+ this.key = key;
+ this.sequenceNumber = sequenceNumber;
+ this.ins = ins;
+ this.lengths = lengths;
+ }
+
+ /**
+ * 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 Editor edit() throws IOException {
+ return DiskLruCache.this.edit(key, sequenceNumber);
+ }
+
+ /** Returns the unbuffered stream with the value for {@code index}. */
+ public InputStream getInputStream(int index) {
+ return ins[index];
+ }
+
+ /** Returns the string value for {@code index}. */
+ public String getString(int index) throws IOException {
+ return inputStreamToString(getInputStream(index));
+ }
+
+ /** Returns the byte length of the value for {@code index}. */
+ public long getLength(int index) {
+ return lengths[index];
+ }
+
+ public void close() {
+ for (InputStream in : ins) {
+ Util.closeQuietly(in);
+ }
+ }
+ }
+
+ private static final OutputStream NULL_OUTPUT_STREAM = new OutputStream() {
+ @Override
+ public void write(int b) throws IOException {
+ // Eat all writes silently. Nom nom.
+ }
+ };
+
+ /** Edits the values for an entry. */
+ public final class Editor {
+ private final Entry entry;
+ private final boolean[] written;
+ private boolean hasErrors;
+ private boolean committed;
+
+ private Editor(Entry entry) {
+ this.entry = entry;
+ this.written = (entry.readable) ? null : new boolean[valueCount];
+ }
+
+ /**
+ * Returns an unbuffered input stream to read the last committed value,
+ * or null if no value has been committed.
+ */
+ public InputStream newInputStream(int index) throws IOException {
+ synchronized (DiskLruCache.this) {
+ if (entry.currentEditor != this) {
+ throw new IllegalStateException();
+ }
+ if (!entry.readable) {
+ return null;
+ }
+ try {
+ return new FileInputStream(entry.getCleanFile(index));
+ } catch (FileNotFoundException e) {
+ return null;
+ }
+ }
+ }
+
+ /**
+ * Returns the last committed value as a string, or null if no value
+ * has been committed.
+ */
+ public String getString(int index) throws IOException {
+ InputStream in = newInputStream(index);
+ return in != null ? inputStreamToString(in) : 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 OutputStream newOutputStream(int index) throws IOException {
+ if (index < 0 || index >= valueCount) {
+ throw new IllegalArgumentException("Expected index " + index + " to "
+ + "be greater than 0 and less than the maximum value count "
+ + "of " + valueCount);
+ }
+ synchronized (DiskLruCache.this) {
+ if (entry.currentEditor != this) {
+ throw new IllegalStateException();
+ }
+ if (!entry.readable) {
+ written[index] = true;
+ }
+ File dirtyFile = entry.getDirtyFile(index);
+ FileOutputStream outputStream;
+ try {
+ outputStream = new FileOutputStream(dirtyFile);
+ } catch (FileNotFoundException e) {
+ // Attempt to recreate the cache directory.
+ directory.mkdirs();
+ try {
+ outputStream = new FileOutputStream(dirtyFile);
+ } catch (FileNotFoundException e2) {
+ // We are unable to recover. Silently eat the writes.
+ return NULL_OUTPUT_STREAM;
+ }
+ }
+ return new FaultHidingOutputStream(outputStream);
+ }
+ }
+
+ /** Sets the value at {@code index} to {@code value}. */
+ public void set(int index, String value) throws IOException {
+ Writer writer = null;
+ try {
+ writer = new OutputStreamWriter(newOutputStream(index), Util.UTF_8);
+ writer.write(value);
+ } finally {
+ Util.closeQuietly(writer);
+ }
+ }
+
+ /**
+ * 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 {
+ if (hasErrors) {
+ completeEdit(this, false);
+ remove(entry.key); // The previous entry is stale.
+ } else {
+ completeEdit(this, true);
+ }
+ committed = true;
+ }
+
+ /**
+ * Aborts this edit. This releases the edit lock so another edit may be
+ * started on the same key.
+ */
+ public void abort() throws IOException {
+ completeEdit(this, false);
+ }
+
+ public void abortUnlessCommitted() {
+ if (!committed) {
+ try {
+ abort();
+ } catch (IOException ignored) {
+ }
+ }
+ }
+
+ private class FaultHidingOutputStream extends FilterOutputStream {
+ private FaultHidingOutputStream(OutputStream out) {
+ super(out);
+ }
+
+ @Override public void write(int oneByte) {
+ try {
+ out.write(oneByte);
+ } catch (IOException e) {
+ hasErrors = true;
+ }
+ }
+
+ @Override public void write(byte[] buffer, int offset, int length) {
+ try {
+ out.write(buffer, offset, length);
+ } catch (IOException e) {
+ hasErrors = true;
+ }
+ }
+
+ @Override public void close() {
+ try {
+ out.close();
+ } catch (IOException e) {
+ hasErrors = true;
+ }
+ }
+
+ @Override public void flush() {
+ try {
+ out.flush();
+ } catch (IOException e) {
+ hasErrors = true;
+ }
+ }
+ }
+ }
+
+ private final class Entry {
+ private final String key;
+
+ /** Lengths of this entry's files. */
+ private final long[] lengths;
+
+ /** True if this entry has ever been published. */
+ private boolean readable;
+
+ /** The ongoing edit or null if this entry is not being edited. */
+ private Editor currentEditor;
+
+ /** The sequence number of the most recently committed edit to this entry. */
+ private long sequenceNumber;
+
+ private Entry(String key) {
+ this.key = key;
+ this.lengths = new long[valueCount];
+ }
+
+ public String getLengths() throws IOException {
+ StringBuilder result = new StringBuilder();
+ for (long size : lengths) {
+ result.append(' ').append(size);
+ }
+ return result.toString();
+ }
+
+ /** Set lengths using decimal numbers like "10123". */
+ private 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);
+ }
+ }
+
+ private IOException invalidLengths(String[] strings) throws IOException {
+ throw new IOException("unexpected journal line: " + java.util.Arrays.toString(strings));
+ }
+
+ public File getCleanFile(int i) {
+ return new File(directory, key + "." + i);
+ }
+
+ public File getDirtyFile(int i) {
+ return new File(directory, key + "." + i + ".tmp");
+ }
+ }
+}