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/* * Copyright (C) 2011 The Android Open Source Project */* ww w.j a v a 2 s . com*/ * 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.baasbox.android.impl; import java.io.*; 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_-]{1,64}</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/> * <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/> * <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/> * <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/> * <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/> * <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 { // ------------------------------ FIELDS ------------------------------ 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_-]{1,64}"); private static final String CLEAN = "CLEAN"; private static final String DIRTY = "DIRTY"; private static final String REMOVE = "REMOVE"; private static final String READ = "READ"; private static final OutputStream NULL_OUTPUT_STREAM = new OutputStream() { @Override public void write(int b) throws IOException { // Eat all writes silently. Nom nom. } }; /** * This cache uses a single background thread to evict entries. */ final ThreadPoolExecutor executorService = new ThreadPoolExecutor(0, 1, 60L, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>()); /* * 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; 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; } }; // --------------------------- CONSTRUCTORS --------------------------- 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; } // -------------------------- STATIC METHODS -------------------------- /** * 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(); cache.journalWriter = new BufferedWriter( new OutputStreamWriter(new FileOutputStream(cache.journalFile, true), Util.US_ASCII)); 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 static void renameTo(File from, File to, boolean deleteDestination) throws IOException { if (deleteDestination) { deleteIfExists(to); } if (!from.renameTo(to)) { throw new IOException(); } } private static void deleteIfExists(File file) throws IOException { if (file.exists() && !file.delete()) { throw new IOException(); } } 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(); } 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(); } } } /** * 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); } /** * 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; } /** * 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 String inputStreamToString(InputStream in) throws IOException { return Util.readFully(new InputStreamReader(in, Util.UTF_8)); } // --------------------- GETTER / SETTER METHODS --------------------- /** * 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; } // -------------------------- OTHER METHODS -------------------------- 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(); } /** * 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; } private void checkNotClosed() { if (journalWriter == null) { throw new IllegalStateException("cache is closed"); } } 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_-]{1,64}: \"" + key + "\""); } } /** * Force buffered operations to the filesystem. */ public synchronized void flush() throws IOException { checkNotClosed(); trimToSize(); journalWriter.flush(); } private void trimToSize() throws IOException { while (size > maxSize) { Map.Entry<String, Entry> toEvict = lruEntries.entrySet().iterator().next(); remove(toEvict.getKey()); } } /** * 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 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 true if this cache has been closed. */ public synchronized boolean isClosed() { return journalWriter == null; } /** * 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; } // -------------------------- INNER CLASSES -------------------------- /** * 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); } } } /** * 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 { 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"); } } }