开发一个app,特别是图片的app,免不了要存储图片,内存缓存是必要的,之前的几篇文章已经有涉及.磁盘的缓存,也是相当必要的.
最近在做一个机顶盒应用,结果,机顶盒的sdcard真烂,导致整个程序的速度被影响了. 报怨一下,这么差的卡就不要拿出来丢人了.
图片下载中,使用了磁盘缓存.android系统中有一个可供使用的缓存类,是个不错的选择.
DiskLruCache
直接上代码吧,
具体的代码可以查看apollo 程序,git上有源码,也可以直接搜索disklrucache.这个缓存策略多数情况是可用的,还带有渐变效果,是个不错的选择.然而我在使用时,出现崩溃的状况,程序因为jni异常,直接退出,大概是同时操作了一个磁盘文件,所以有限制线程数,看上去是必要的.同时,如果加载的图片都是大图片,不可避免会有oome出现.比如微博程序,时间线查看图片都是大图就会出现.它还是不可直接使用,需要改造.稍后有时间,把整个缓存打包与library工程,直接供外界使用.class ImageCache: /** * Default disk cache size 10MB */ private static final int DISK_CACHE_SIZE = 1024 * 1024 * 10; /** * Compression settings when writing images to disk cache */ private static final CompressFormat COMPRESS_FORMAT = CompressFormat.JPEG; /** * Disk cache index to read from */ private static final int DISK_CACHE_INDEX = 0; /** * Image compression quality */ private static final int COMPRESS_QUALITY = 98;下面初始化需要在非ui线程中运行,public void initDiskCache(final Context context) { // Set up disk cache if (mDiskCache == null || mDiskCache.isClosed()) { File diskCacheDir = getDiskCacheDir(context, TAG); if (diskCacheDir != null) { if (!diskCacheDir.exists()) { diskCacheDir.mkdirs(); } if (getUsableSpace(diskCacheDir) > DISK_CACHE_SIZE) { try { mDiskCache = DiskLruCache.open(diskCacheDir, 1, 1, DISK_CACHE_SIZE); } catch (final IOException e) { diskCacheDir = null; } } } } }public static final File getDiskCacheDir(final Context context, final String uniqueName) { final String cachePath = Environment.MEDIA_MOUNTED.equals(Environment .getExternalStorageState()) || !isExternalStorageRemovable() ? getExternalCacheDir( context).getPath() : context.getCacheDir().getPath(); return new File(cachePath + File.separator + uniqueName); }不必太在意上面有些方法找不到. getExternalCacheDir(context).getPath() 取得sdcard上的一个缓存目录,因为这个磁盘缓存是可控制大小的,所以,如果不需要太大的缓存空间,还是使用context.getCacheDir().getPath(),即/data/data/下的目录,至少可以保证程序的运行速度,因为有些sdcard真是烂.下面的策略,大概是下载图片,然后图片存储,存储时生成一个序列值,然后写到日志文件中.外部调用的方法,获取缓存图片,这在下载前检测的.public final Bitmap getCachedBitmap(final String data) { if (data == null) { return null; } Bitmap cachedImage = getBitmapFromMemCache(data); if (cachedImage == null) { cachedImage = getBitmapFromDiskCache(data); } if (cachedImage != null) { addBitmapToMemCache(data, cachedImage); return cachedImage; } return null; }从磁盘检测public final Bitmap getBitmapFromDiskCache(final String data) { if (data == null) { return null; } // Check in the memory cache here to avoid going to the disk cache less // often if (getBitmapFromMemCache(data) != null) { return getBitmapFromMemCache(data); } while (mPauseDiskAccess) { // Pause for moment } final String key = hashKeyForDisk(data);//md5生成key if (mDiskCache != null) { InputStream inputStream = null; try { final DiskLruCache.Snapshot snapshot = mDiskCache.get(key); if (snapshot != null) { inputStream = snapshot.getInputStream(DISK_CACHE_INDEX); if (inputStream != null) { final Bitmap bitmap = BitmapFactory.decodeStream(inputStream); if (bitmap != null) { return bitmap; } } } } catch (final IOException e) { Log.e(TAG, "getBitmapFromDiskCache - " + e); } finally { try { if (inputStream != null) { inputStream.close(); } } catch (final IOException e) { } } } return null; }添加图片到缓存中,不仅到内存缓存中,而且添加到磁盘缓存中.public void addBitmapToCache(final String data, final Bitmap bitmap) { if (data == null || bitmap == null) { return; } // Add to memory cache addBitmapToMemCache(data, bitmap); // Add to disk cache if (mDiskCache != null) { final String key = hashKeyForDisk(data); OutputStream out = null; try { final DiskLruCache.Snapshot snapshot = mDiskCache.get(key); if (snapshot == null) { final DiskLruCache.Editor editor = mDiskCache.edit(key); if (editor != null) { out = editor.newOutputStream(DISK_CACHE_INDEX); bitmap.compress(COMPRESS_FORMAT, COMPRESS_QUALITY, out); editor.commit(); out.close(); flush(); } } else { snapshot.getInputStream(DISK_CACHE_INDEX).close(); } } catch (final IOException e) { Log.e(TAG, "addBitmapToCache - " + e); } finally { try { if (out != null) { out.close(); out = null; } } catch (final IOException e) { Log.e(TAG, "addBitmapToCache - " + e); } catch (final IllegalStateException e) { Log.e(TAG, "addBitmapToCache - " + e); } } } }====================================import java.io.BufferedInputStream;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.FileWriter;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.Reader;import java.io.StringWriter;import java.io.Writer;import java.lang.reflect.Array;import java.nio.charset.Charset;import java.util.ArrayList;import java.util.Arrays;import java.util.Iterator;import java.util.LinkedHashMap;import java.util.Map;import java.util.concurrent.Callable;import java.util.concurrent.ExecutorService;import java.util.concurrent.LinkedBlockingQueue;import java.util.concurrent.ThreadPoolExecutor;import java.util.concurrent.TimeUnit;/** ****************************************************************************** Taken from the JB source code, can be found in: * libcore/luni/src/main/java/libcore/io/DiskLruCache.java or direct link: * https: * //android.googlesource.com/platform/libcore/+/android-4.1.1_r1/luni/src/ * main/java/libcore/io/DiskLruCache.java 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. Values are byte sequences, accessible as streams or files. Each * value must be between [email protected] 0} and [email protected] 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 [email protected] #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 [email protected] #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 [email protected] #edit} call must be matched by a call to [email protected] Editor#commit} * or [email protected] 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 [email protected] #get} to read a snapshot of an entry. The read will * observe the value at the time that [email protected] #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 [email protected] IOException} and * responding appropriately. */public final class DiskLruCache implements Closeable { static final String JOURNAL_FILE = "journal"; static final String JOURNAL_FILE_TMP = "journal.tmp"; static final String MAGIC = "libcore.io.DiskLruCache"; static final String VERSION_1 = "1"; static final long ANY_SEQUENCE_NUMBER = -1; 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 Charset UTF_8 = Charset.forName("UTF-8"); private static final int IO_BUFFER_SIZE = 8 * 1024; /* * 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 int appVersion; private final 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; /* From java.util.Arrays */ @SuppressWarnings("unchecked") private static <T> T[] copyOfRange(final T[] original, final int start, final int end) { final int originalLength = original.length; // For exception priority // compatibility. if (start > end) { throw new IllegalArgumentException(); } if (start < 0 || start > originalLength) { throw new ArrayIndexOutOfBoundsException(); } final int resultLength = end - start; final int copyLength = Math.min(resultLength, originalLength - start); final T[] result = (T[])Array.newInstance(original.getClass().getComponentType(), resultLength); System.arraycopy(original, start, result, 0, copyLength); return result; } /** * Returns the remainder of 'reader' as a string, closing it when done. */ public static String readFully(final Reader reader) throws IOException { try { final StringWriter writer = new StringWriter(); final char[] buffer = new char[1024]; int count; while ((count = reader.read(buffer)) != -1) { writer.write(buffer, 0, count); } return writer.toString(); } finally { reader.close(); } } /** * Returns the ASCII characters up to but not including the next "\r\n", or * "\n". * * @throws java.io.EOFException if the stream is exhausted before the next * newline character. */ public static String readAsciiLine(final InputStream in) throws IOException { // TODO: support UTF-8 here instead final StringBuilder result = new StringBuilder(80); while (true) { final int c = in.read(); if (c == -1) { throw new EOFException(); } else if (c == '\n') { break; } result.append((char)c); } final int length = result.length(); if (length > 0 && result.charAt(length - 1) == '\r') { result.setLength(length - 1); } return result.toString(); } /** * Closes 'closeable', ignoring any checked exceptions. Does nothing if * 'closeable' is null. */ public static void closeQuietly(final Closeable closeable) { if (closeable != null) { try { closeable.close(); } catch (final RuntimeException rethrown) { throw rethrown; } catch (final Exception ignored) { } } } /** * Recursively delete everything in [email protected] dir}. */ // TODO: this should specify paths as Strings rather than as Files public static void deleteContents(final File dir) throws IOException { final File[] files = dir.listFiles(); if (files == null) { throw new IllegalArgumentException("not a directory: " + dir); } for (final File file : files) { if (file.isDirectory()) { deleteContents(file); } if (!file.delete()) { throw new IOException("failed to delete file: " + file); } } } /** This cache uses a single background thread to evict entries. */ private final ExecutorService executorService = new ThreadPoolExecutor(0, 1, 60L, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>()); private final Callable<Void> cleanupCallable = new Callable<Void>() { @Override public Void call() throws Exception { synchronized (DiskLruCache.this) { if (journalWriter == null) { return null; // closed } trimToSize(); if (journalRebuildRequired()) { rebuildJournal(); redundantOpCount = 0; } } return null; } }; private DiskLruCache(final File directory, final int appVersion, final int valueCount, final long maxSize) { this.directory = directory; this.appVersion = appVersion; journalFile = new File(directory, JOURNAL_FILE); journalFileTmp = new File(directory, JOURNAL_FILE_TMP); this.valueCount = valueCount; this.maxSize = maxSize; } /** * Opens the cache in [email protected] directory}, creating a cache if none exists * there. * * @param directory a writable directory * @param appVersion * @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(final File directory, final int appVersion, final int valueCount, final long maxSize) throws IOException { if (maxSize <= 0) { throw new IllegalArgumentException("maxSize <= 0"); } if (valueCount <= 0) { throw new IllegalArgumentException("valueCount <= 0"); } // 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 FileWriter(cache.journalFile, true), IO_BUFFER_SIZE); return cache; } catch (final IOException journalIsCorrupt) { // System.logW("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 { final InputStream in = new BufferedInputStream(new FileInputStream(journalFile), IO_BUFFER_SIZE); try { final String magic = readAsciiLine(in); final String version = readAsciiLine(in); final String appVersionString = readAsciiLine(in); final String valueCountString = readAsciiLine(in); final String blank = readAsciiLine(in); 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 + "]"); } while (true) { try { readJournalLine(readAsciiLine(in)); } catch (final EOFException endOfJournal) { break; } } } finally { closeQuietly(in); } } private void readJournalLine(final String line) throws IOException { final String[] parts = line.split(" "); if (parts.length < 2) { throw new IOException("unexpected journal line: " + line); } final String key = parts[1]; if (parts[0].equals(REMOVE) && parts.length == 2) { lruEntries.remove(key); return; } Entry entry = lruEntries.get(key); if (entry == null) { entry = new Entry(key); lruEntries.put(key, entry); } if (parts[0].equals(CLEAN) && parts.length == 2 + valueCount) { entry.readable = true; entry.currentEditor = null; entry.setLengths(copyOfRange(parts, 2, parts.length)); } else if (parts[0].equals(DIRTY) && parts.length == 2) { entry.currentEditor = new Editor(entry); } else if (parts[0].equals(READ) && parts.length == 2) { // 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 (final Iterator<Entry> i = lruEntries.values().iterator(); i.hasNext();) { final 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(); } final Writer writer = new BufferedWriter(new FileWriter(journalFileTmp), IO_BUFFER_SIZE); 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 (final Entry entry : lruEntries.values()) { if (entry.currentEditor != null) { writer.write(DIRTY + ' ' + entry.key + '\n'); } else { writer.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n'); } } writer.close(); journalFileTmp.renameTo(journalFile); journalWriter = new BufferedWriter(new FileWriter(journalFile, true), IO_BUFFER_SIZE); } private static void deleteIfExists(final File file) throws IOException { // try { // Libcore.os.remove(file.getPath()); // } catch (ErrnoException errnoException) { // if (errnoException.errno != OsConstants.ENOENT) { // throw errnoException.rethrowAsIOException(); // } // } if (file.exists() && !file.delete()) { throw new IOException(); } } /** * Returns a snapshot of the entry named [email protected] 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(final String key) throws IOException { checkNotClosed(); validateKey(key); final 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. */ final InputStream[] ins = new InputStream[valueCount]; try { for (int i = 0; i < valueCount; i++) { ins[i] = new FileInputStream(entry.getCleanFile(i)); } } catch (final FileNotFoundException e) { // a file must have been deleted manually! return null; } redundantOpCount++; journalWriter.append(READ + ' ' + key + '\n'); if (journalRebuildRequired()) { executorService.submit(cleanupCallable); } return new Snapshot(key, entry.sequenceNumber, ins); } /** * Returns an editor for the entry named [email protected] key}, or null if another * edit is in progress. */ public Editor edit(final String key) throws IOException { return edit(key, ANY_SEQUENCE_NUMBER); } private synchronized Editor edit(final String key, final 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 } final 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 long maxSize() { return maxSize; } /** * 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(final Editor editor, final boolean success) throws IOException { final 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 (!entry.getDirtyFile(i).exists()) { editor.abort(); throw new IllegalStateException("edit didn't create file " + i); } } } for (int i = 0; i < valueCount; i++) { final File dirty = entry.getDirtyFile(i); if (success) { if (dirty.exists()) { final File clean = entry.getCleanFile(i); dirty.renameTo(clean); final long oldLength = entry.lengths[i]; final 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'); } 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 REDUNDANT_OP_COMPACT_THRESHOLD = 2000; return redundantOpCount >= REDUNDANT_OP_COMPACT_THRESHOLD && redundantOpCount >= lruEntries.size(); } /** * Drops the entry for [email protected] 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(final String key) throws IOException { checkNotClosed(); validateKey(key); final Entry entry = lruEntries.get(key); if (entry == null || entry.currentEditor != null) { return false; } for (int i = 0; i < valueCount; i++) { final File file = entry.getCleanFile(i); if (!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 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. */ @Override public synchronized void close() throws IOException { if (journalWriter == null) { return; // already closed } for (final 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.eldest(); final 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(); deleteContents(directory); } private void validateKey(final String key) { if (key.contains(" ") || key.contains("\n") || key.contains("\r")) { throw new IllegalArgumentException("keys must not contain spaces or newlines: \"" + key + "\""); } } private static String inputStreamToString(final InputStream in) throws IOException { return readFully(new InputStreamReader(in, 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 Snapshot(final String key, final long sequenceNumber, final InputStream[] ins) { this.key = key; this.sequenceNumber = sequenceNumber; this.ins = ins; } /** * 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 [email protected] index}. */ public InputStream getInputStream(final int index) { return ins[index]; } /** * Returns the string value for [email protected] index}. */ public String getString(final int index) throws IOException { return inputStreamToString(getInputStream(index)); } @Override public void close() { for (final InputStream in : ins) { closeQuietly(in); } } } /** * Edits the values for an entry. */ public final class Editor { private final Entry entry; private boolean hasErrors; private Editor(final Entry entry) { this.entry = entry; } /** * Returns an unbuffered input stream to read the last committed value, * or null if no value has been committed. */ public InputStream newInputStream(final int index) throws IOException { synchronized (DiskLruCache.this) { if (entry.currentEditor != this) { throw new IllegalStateException(); } if (!entry.readable) { return null; } return new FileInputStream(entry.getCleanFile(index)); } } /** * Returns the last committed value as a string, or null if no value has * been committed. */ public String getString(final int index) throws IOException { final InputStream in = newInputStream(index); return in != null ? inputStreamToString(in) : null; } /** * Returns a new unbuffered output stream to write the value at * [email protected] index}. If the underlying output stream encounters errors when * writing to the filesystem, this edit will be aborted when * [email protected] #commit} is called. The returned output stream does not throw * IOExceptions. */ public OutputStream newOutputStream(final int index) throws IOException { synchronized (DiskLruCache.this) { if (entry.currentEditor != this) { throw new IllegalStateException(); } return new FaultHidingOutputStream(new FileOutputStream(entry.getDirtyFile(index))); } } /** * Sets the value at [email protected] index} to [email protected] value}. */ public void set(final int index, final String value) throws IOException { Writer writer = null; try { writer = new OutputStreamWriter(newOutputStream(index), UTF_8); writer.write(value); } finally { 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); } } /** * 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); } private class FaultHidingOutputStream extends FilterOutputStream { private FaultHidingOutputStream(final OutputStream out) { super(out); } @Override public void write(final int oneByte) { try { out.write(oneByte); } catch (final IOException e) { hasErrors = true; } } @Override public void write(final byte[] buffer, final int offset, final int length) { try { out.write(buffer, offset, length); } catch (final IOException e) { hasErrors = true; } } @Override public void close() { try { out.close(); } catch (final IOException e) { hasErrors = true; } } @Override public void flush() { try { out.flush(); } catch (final 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(final String key) { this.key = key; lengths = new long[valueCount]; } public String getLengths() throws IOException { final StringBuilder result = new StringBuilder(); for (final long size : lengths) { result.append(' ').append(size); } return result.toString(); } /** * Set lengths using decimal numbers like "10123". */ private void setLengths(final 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 (final NumberFormatException e) { throw invalidLengths(strings); } } private IOException invalidLengths(final String[] strings) throws IOException { throw new IOException("unexpected journal line: " + Arrays.toString(strings)); } public File getCleanFile(final int i) { return new File(directory, key + "." + i); } public File getDirtyFile(final int i) { return new File(directory, key + "." + i + ".tmp"); } }}