Java tutorial
/* * 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.squareup.okhttp.internal; import com.squareup.okhttp.internal.io.FileSystem; import java.io.Closeable; import java.io.EOFException; import java.io.File; import java.io.FileNotFoundException; 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 okio.Buffer; import okio.BufferedSink; import okio.BufferedSource; import okio.Okio; import okio.Sink; import okio.Source; import okio.Timeout; /** * 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_-]{1,64}</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 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. */ private final FileSystem fileSystem; 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 BufferedSink journalWriter; private final LinkedHashMap<String, Entry> lruEntries = new LinkedHashMap<>(0, 0.75f, true); private int redundantOpCount; private boolean hasJournalErrors; // Must be read and written when synchronized on 'this'. private boolean initialized; private boolean closed; /** * 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(); if (journalRebuildRequired()) { rebuildJournal(); redundantOpCount = 0; } } catch (IOException e) { throw new RuntimeException(e); } } } }; 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().logW("DiskLruCache " + directory + " is corrupt: " + journalIsCorrupt.getMessage() + ", removing"); delete(); 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<Runnable>(), 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<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++) { 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. */ private 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; } /** * 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 Editor edit(String key) throws IOException { return edit(key, ANY_SEQUENCE_NUMBER); } private 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. } // 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; } 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 (!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. */ 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. 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; return removeEntry(entry); } private boolean removeEntry(Entry entry) throws IOException { if (entry.currentEditor != null) { entry.currentEditor.hasErrors = true; // 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. */ public synchronized void flush() throws IOException { if (!initialized) return; checkNotClosed(); trimToSize(); journalWriter.flush(); } /** Closes this cache. Stored values will remain on the filesystem. */ 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; } private void trimToSize() throws IOException { while (size > maxSize) { Entry toEvict = lruEntries.values().iterator().next(); removeEntry(toEvict); } } /** * 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); } } 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). * * <p>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. * * <p><strong>The caller must {@link Snapshot#close close}</strong> each snapshot returned by * {@link Iterator#next}. Failing to do so leaks open files! * * <p>The returned iterator supports {@link Iterator#remove}. */ public synchronized Iterator<Snapshot> snapshots() throws IOException { initialize(); return new Iterator<Snapshot>() { /** Iterate a copy of the entries to defend against concurrent modification errors. */ final Iterator<Entry> 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; private 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 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); } } } private static final Sink NULL_SINK = new Sink() { @Override public void write(Buffer source, long byteCount) throws IOException { source.skip(byteCount); } @Override public void flush() throws IOException { } @Override public Timeout timeout() { return Timeout.NONE; } @Override public void close() throws IOException { } }; /** 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 Source newSource(int index) throws IOException { synchronized (DiskLruCache.this) { if (entry.currentEditor != this) { throw new IllegalStateException(); } if (!entry.readable) { 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) throws IOException { synchronized (DiskLruCache.this) { if (entry.currentEditor != this) { throw new IllegalStateException(); } if (!entry.readable) { written[index] = true; } File dirtyFile = entry.dirtyFiles[index]; Sink sink; try { sink = fileSystem.sink(dirtyFile); } catch (FileNotFoundException e) { return NULL_SINK; } return new FaultHidingSink(sink) { @Override protected void onException(IOException e) { synchronized (DiskLruCache.this) { hasErrors = true; } } }; } } /** * 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 (hasErrors) { completeEdit(this, false); removeEntry(entry); // 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 { synchronized (DiskLruCache.this) { completeEdit(this, false); } } public void abortUnlessCommitted() { synchronized (DiskLruCache.this) { if (!committed) { try { completeEdit(this, false); } catch (IOException ignored) { } } } } } private final class Entry { private final String key; /** Lengths of this entry's files. */ private final long[] lengths; private final File[] cleanFiles; private final File[] dirtyFiles; /** 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; 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". */ 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); } } /** 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; } } return null; } } } }