1 /*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package com.example.photoswall;
18
19 import java.io.BufferedInputStream;
20 import java.io.BufferedWriter;
21 import java.io.Closeable;
22 import java.io.EOFException;
23 import java.io.File;
24 import java.io.FileInputStream;
25 import java.io.FileNotFoundException;
26 import java.io.FileOutputStream;
27 import java.io.FileWriter;
28 import java.io.FilterOutputStream;
29 import java.io.IOException;
30 import java.io.InputStream;
31 import java.io.InputStreamReader;
32 import java.io.OutputStream;
33 import java.io.OutputStreamWriter;
34 import java.io.Reader;
35 import java.io.StringWriter;
36 import java.io.Writer;
37 import java.lang.reflect.Array;
38 import java.nio.charset.Charset;
39 import java.util.ArrayList;
40 import java.util.Arrays;
41 import java.util.Iterator;
42 import java.util.LinkedHashMap;
43 import java.util.Map;
44 import java.util.concurrent.Callable;
45 import java.util.concurrent.ExecutorService;
46 import java.util.concurrent.LinkedBlockingQueue;
47 import java.util.concurrent.ThreadPoolExecutor;
48 import java.util.concurrent.TimeUnit;
49
50 /**
51 ******************************************************************************
52 * Taken from the JB source code, can be found in:
53 * libcore/luni/src/main/java/libcore/io/DiskLruCache.java
54 * or direct link:
55 * https://android.googlesource.com/platform/libcore/+/android-4.1.1_r1/luni/src/main/java/libcore/io/DiskLruCache.java
56 ******************************************************************************
57 *
58 * A cache that uses a bounded amount of space on a filesystem. Each cache
59 * entry has a string key and a fixed number of values. Values are byte
60 * sequences, accessible as streams or files. Each value must be between {@code
61 * 0} and {@code Integer.MAX_VALUE} bytes in length.
62 *
63 * <p>The cache stores its data in a directory on the filesystem. This
64 * directory must be exclusive to the cache; the cache may delete or overwrite
65 * files from its directory. It is an error for multiple processes to use the
66 * same cache directory at the same time.
67 *
68 * <p>This cache limits the number of bytes that it will store on the
69 * filesystem. When the number of stored bytes exceeds the limit, the cache will
70 * remove entries in the background until the limit is satisfied. The limit is
71 * not strict: the cache may temporarily exceed it while waiting for files to be
72 * deleted. The limit does not include filesystem overhead or the cache
73 * journal so space-sensitive applications should set a conservative limit.
74 *
75 * <p>Clients call {@link #edit} to create or update the values of an entry. An
76 * entry may have only one editor at one time; if a value is not available to be
77 * edited then {@link #edit} will return null.
78 * <ul>
79 * <li>When an entry is being <strong>created</strong> it is necessary to
80 * supply a full set of values; the empty value should be used as a
81 * placeholder if necessary.
82 * <li>When an entry is being <strong>edited</strong>, it is not necessary
83 * to supply data for every value; values default to their previous
84 * value.
85 * </ul>
86 * Every {@link #edit} call must be matched by a call to {@link Editor#commit}
87 * or {@link Editor#abort}. Committing is atomic: a read observes the full set
88 * of values as they were before or after the commit, but never a mix of values.
89 *
90 * <p>Clients call {@link #get} to read a snapshot of an entry. The read will
91 * observe the value at the time that {@link #get} was called. Updates and
92 * removals after the call do not impact ongoing reads.
93 *
94 * <p>This class is tolerant of some I/O errors. If files are missing from the
95 * filesystem, the corresponding entries will be dropped from the cache. If
96 * an error occurs while writing a cache value, the edit will fail silently.
97 * Callers should handle other problems by catching {@code IOException} and
98 * responding appropriately.
99 */
100 public final class DiskLruCache implements Closeable {
101 static final String JOURNAL_FILE = "journal";
102 static final String JOURNAL_FILE_TMP = "journal.tmp";
103 static final String MAGIC = "libcore.io.DiskLruCache";
104 static final String VERSION_1 = "1";
105 static final long ANY_SEQUENCE_NUMBER = -1;
106 private static final String CLEAN = "CLEAN";
107 private static final String DIRTY = "DIRTY";
108 private static final String REMOVE = "REMOVE";
109 private static final String READ = "READ";
110
111 private static final Charset UTF_8 = Charset.forName("UTF-8");
112 private static final int IO_BUFFER_SIZE = 8 * 1024;
113
114 /*
115 * This cache uses a journal file named "journal". A typical journal file
116 * looks like this:
117 * libcore.io.DiskLruCache
118 * 1
119 * 100
120 * 2
121 *
122 * CLEAN 3400330d1dfc7f3f7f4b8d4d803dfcf6 832 21054
123 * DIRTY 335c4c6028171cfddfbaae1a9c313c52
124 * CLEAN 335c4c6028171cfddfbaae1a9c313c52 3934 2342
125 * REMOVE 335c4c6028171cfddfbaae1a9c313c52
126 * DIRTY 1ab96a171faeeee38496d8b330771a7a
127 * CLEAN 1ab96a171faeeee38496d8b330771a7a 1600 234
128 * READ 335c4c6028171cfddfbaae1a9c313c52
129 * READ 3400330d1dfc7f3f7f4b8d4d803dfcf6
130 *
131 * The first five lines of the journal form its header. They are the
132 * constant string "libcore.io.DiskLruCache", the disk cache's version,
133 * the application's version, the value count, and a blank line.
134 *
135 * Each of the subsequent lines in the file is a record of the state of a
136 * cache entry. Each line contains space-separated values: a state, a key,
137 * and optional state-specific values.
138 * o DIRTY lines track that an entry is actively being created or updated.
139 * Every successful DIRTY action should be followed by a CLEAN or REMOVE
140 * action. DIRTY lines without a matching CLEAN or REMOVE indicate that
141 * temporary files may need to be deleted.
142 * o CLEAN lines track a cache entry that has been successfully published
143 * and may be read. A publish line is followed by the lengths of each of
144 * its values.
145 * o READ lines track accesses for LRU.
146 * o REMOVE lines track entries that have been deleted.
147 *
148 * The journal file is appended to as cache operations occur. The journal may
149 * occasionally be compacted by dropping redundant lines. A temporary file named
150 * "journal.tmp" will be used during compaction; that file should be deleted if
151 * it exists when the cache is opened.
152 */
153
154 private final File directory;
155 private final File journalFile;
156 private final File journalFileTmp;
157 private final int appVersion;
158 private final long maxSize;
159 private final int valueCount;
160 private long size = 0;
161 private Writer journalWriter;
162 private final LinkedHashMap<String, Entry> lruEntries
163 = new LinkedHashMap<String, Entry>(0, 0.75f, true);
164 private int redundantOpCount;
165
166 /**
167 * To differentiate between old and current snapshots, each entry is given
168 * a sequence number each time an edit is committed. A snapshot is stale if
169 * its sequence number is not equal to its entry's sequence number.
170 */
171 private long nextSequenceNumber = 0;
172
173 /* From java.util.Arrays */
174 @SuppressWarnings("unchecked")
175 private static <T> T[] copyOfRange(T[] original, int start, int end) {
176 final int originalLength = original.length; // For exception priority compatibility.
177 if (start > end) {
178 throw new IllegalArgumentException();
179 }
180 if (start < 0 || start > originalLength) {
181 throw new ArrayIndexOutOfBoundsException();
182 }
183 final int resultLength = end - start;
184 final int copyLength = Math.min(resultLength, originalLength - start);
185 final T[] result = (T[]) Array
186 .newInstance(original.getClass().getComponentType(), resultLength);
187 System.arraycopy(original, start, result, 0, copyLength);
188 return result;
189 }
190
191 /**
192 * Returns the remainder of 'reader' as a string, closing it when done.
193 */
194 public static String readFully(Reader reader) throws IOException {
195 try {
196 StringWriter writer = new StringWriter();
197 char[] buffer = new char[1024];
198 int count;
199 while ((count = reader.read(buffer)) != -1) {
200 writer.write(buffer, 0, count);
201 }
202 return writer.toString();
203 } finally {
204 reader.close();
205 }
206 }
207
208 /**
209 * Returns the ASCII characters up to but not including the next "\r\n", or
210 * "\n".
211 *
212 * @throws java.io.EOFException if the stream is exhausted before the next newline
213 * character.
214 */
215 public static String readAsciiLine(InputStream in) throws IOException {
216 // TODO: support UTF-8 here instead
217
218 StringBuilder result = new StringBuilder(80);
219 while (true) {
220 int c = in.read();
221 if (c == -1) {
222 throw new EOFException();
223 } else if (c == '\n') {
224 break;
225 }
226
227 result.append((char) c);
228 }
229 int length = result.length();
230 if (length > 0 && result.charAt(length - 1) == '\r') {
231 result.setLength(length - 1);
232 }
233 return result.toString();
234 }
235
236 /**
237 * Closes 'closeable', ignoring any checked exceptions. Does nothing if 'closeable' is null.
238 */
239 public static void closeQuietly(Closeable closeable) {
240 if (closeable != null) {
241 try {
242 closeable.close();
243 } catch (RuntimeException rethrown) {
244 throw rethrown;
245 } catch (Exception ignored) {
246 }
247 }
248 }
249
250 /**
251 * Recursively delete everything in {@code dir}.
252 */
253 // TODO: this should specify paths as Strings rather than as Files
254 public static void deleteContents(File dir) throws IOException {
255 File[] files = dir.listFiles();
256 if (files == null) {
257 throw new IllegalArgumentException("not a directory: " + dir);
258 }
259 for (File file : files) {
260 if (file.isDirectory()) {
261 deleteContents(file);
262 }
263 if (!file.delete()) {
264 throw new IOException("failed to delete file: " + file);
265 }
266 }
267 }
268
269 /** This cache uses a single background thread to evict entries. */
270 private final ExecutorService executorService = new ThreadPoolExecutor(0, 1,
271 60L, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());
272 private final Callable<Void> cleanupCallable = new Callable<Void>() {
273 @Override public Void call() throws Exception {
274 synchronized (DiskLruCache.this) {
275 if (journalWriter == null) {
276 return null; // closed
277 }
278 trimToSize();
279 if (journalRebuildRequired()) {
280 rebuildJournal();
281 redundantOpCount = 0;
282 }
283 }
284 return null;
285 }
286 };
287
288 private DiskLruCache(File directory, int appVersion, int valueCount, long maxSize) {
289 this.directory = directory;
290 this.appVersion = appVersion;
291 this.journalFile = new File(directory, JOURNAL_FILE);
292 this.journalFileTmp = new File(directory, JOURNAL_FILE_TMP);
293 this.valueCount = valueCount;
294 this.maxSize = maxSize;
295 }
296
297 /**
298 * Opens the cache in {@code directory}, creating a cache if none exists
299 * there.
300 *
301 * @param directory a writable directory
302 * @param appVersion
303 * @param valueCount the number of values per cache entry. Must be positive.
304 * @param maxSize the maximum number of bytes this cache should use to store
305 * @throws java.io.IOException if reading or writing the cache directory fails
306 */
307 public static DiskLruCache open(File directory, int appVersion, int valueCount, long maxSize)
308 throws IOException {
309 if (maxSize <= 0) {
310 throw new IllegalArgumentException("maxSize <= 0");
311 }
312 if (valueCount <= 0) {
313 throw new IllegalArgumentException("valueCount <= 0");
314 }
315
316 // prefer to pick up where we left off
317 DiskLruCache cache = new DiskLruCache(directory, appVersion, valueCount, maxSize);
318 if (cache.journalFile.exists()) {
319 try {
320 cache.readJournal();
321 cache.processJournal();
322 cache.journalWriter = new BufferedWriter(new FileWriter(cache.journalFile, true),
323 IO_BUFFER_SIZE);
324 return cache;
325 } catch (IOException journalIsCorrupt) {
326 // System.logW("DiskLruCache " + directory + " is corrupt: "
327 // + journalIsCorrupt.getMessage() + ", removing");
328 cache.delete();
329 }
330 }
331
332 // create a new empty cache
333 directory.mkdirs();
334 cache = new DiskLruCache(directory, appVersion, valueCount, maxSize);
335 cache.rebuildJournal();
336 return cache;
337 }
338
339 private void readJournal() throws IOException {
340 InputStream in = new BufferedInputStream(new FileInputStream(journalFile), IO_BUFFER_SIZE);
341 try {
342 String magic = readAsciiLine(in);
343 String version = readAsciiLine(in);
344 String appVersionString = readAsciiLine(in);
345 String valueCountString = readAsciiLine(in);
346 String blank = readAsciiLine(in);
347 if (!MAGIC.equals(magic)
348 || !VERSION_1.equals(version)
349 || !Integer.toString(appVersion).equals(appVersionString)
350 || !Integer.toString(valueCount).equals(valueCountString)
351 || !"".equals(blank)) {
352 throw new IOException("unexpected journal header: ["
353 + magic + ", " + version + ", " + valueCountString + ", " + blank + "]");
354 }
355
356 while (true) {
357 try {
358 readJournalLine(readAsciiLine(in));
359 } catch (EOFException endOfJournal) {
360 break;
361 }
362 }
363 } finally {
364 closeQuietly(in);
365 }
366 }
367
368 private void readJournalLine(String line) throws IOException {
369 String[] parts = line.split(" ");
370 if (parts.length < 2) {
371 throw new IOException("unexpected journal line: " + line);
372 }
373
374 String key = parts[1];
375 if (parts[0].equals(REMOVE) && parts.length == 2) {
376 lruEntries.remove(key);
377 return;
378 }
379
380 Entry entry = lruEntries.get(key);
381 if (entry == null) {
382 entry = new Entry(key);
383 lruEntries.put(key, entry);
384 }
385
386 if (parts[0].equals(CLEAN) && parts.length == 2 + valueCount) {
387 entry.readable = true;
388 entry.currentEditor = null;
389 entry.setLengths(copyOfRange(parts, 2, parts.length));
390 } else if (parts[0].equals(DIRTY) && parts.length == 2) {
391 entry.currentEditor = new Editor(entry);
392 } else if (parts[0].equals(READ) && parts.length == 2) {
393 // this work was already done by calling lruEntries.get()
394 } else {
395 throw new IOException("unexpected journal line: " + line);
396 }
397 }
398
399 /**
400 * Computes the initial size and collects garbage as a part of opening the
401 * cache. Dirty entries are assumed to be inconsistent and will be deleted.
402 */
403 private void processJournal() throws IOException {
404 deleteIfExists(journalFileTmp);
405 for (Iterator<Entry> i = lruEntries.values().iterator(); i.hasNext(); ) {
406 Entry entry = i.next();
407 if (entry.currentEditor == null) {
408 for (int t = 0; t < valueCount; t++) {
409 size += entry.lengths[t];
410 }
411 } else {
412 entry.currentEditor = null;
413 for (int t = 0; t < valueCount; t++) {
414 deleteIfExists(entry.getCleanFile(t));
415 deleteIfExists(entry.getDirtyFile(t));
416 }
417 i.remove();
418 }
419 }
420 }
421
422 /**
423 * Creates a new journal that omits redundant information. This replaces the
424 * current journal if it exists.
425 */
426 private synchronized void rebuildJournal() throws IOException {
427 if (journalWriter != null) {
428 journalWriter.close();
429 }
430
431 Writer writer = new BufferedWriter(new FileWriter(journalFileTmp), IO_BUFFER_SIZE);
432 writer.write(MAGIC);
433 writer.write("\n");
434 writer.write(VERSION_1);
435 writer.write("\n");
436 writer.write(Integer.toString(appVersion));
437 writer.write("\n");
438 writer.write(Integer.toString(valueCount));
439 writer.write("\n");
440 writer.write("\n");
441
442 for (Entry entry : lruEntries.values()) {
443 if (entry.currentEditor != null) {
444 writer.write(DIRTY + ' ' + entry.key + '\n');
445 } else {
446 writer.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n');
447 }
448 }
449
450 writer.close();
451 journalFileTmp.renameTo(journalFile);
452 journalWriter = new BufferedWriter(new FileWriter(journalFile, true), IO_BUFFER_SIZE);
453 }
454
455 private static void deleteIfExists(File file) throws IOException {
456 // try {
457 // Libcore.os.remove(file.getPath());
458 // } catch (ErrnoException errnoException) {
459 // if (errnoException.errno != OsConstants.ENOENT) {
460 // throw errnoException.rethrowAsIOException();
461 // }
462 // }
463 if (file.exists() && !file.delete()) {
464 throw new IOException();
465 }
466 }
467
468 /**
469 * Returns a snapshot of the entry named {@code key}, or null if it doesn't
470 * exist is not currently readable. If a value is returned, it is moved to
471 * the head of the LRU queue.
472 */
473 public synchronized Snapshot get(String key) throws IOException {
474 checkNotClosed();
475 validateKey(key);
476 Entry entry = lruEntries.get(key);
477 if (entry == null) {
478 return null;
479 }
480
481 if (!entry.readable) {
482 return null;
483 }
484
485 /*
486 * Open all streams eagerly to guarantee that we see a single published
487 * snapshot. If we opened streams lazily then the streams could come
488 * from different edits.
489 */
490 InputStream[] ins = new InputStream[valueCount];
491 try {
492 for (int i = 0; i < valueCount; i++) {
493 ins[i] = new FileInputStream(entry.getCleanFile(i));
494 }
495 } catch (FileNotFoundException e) {
496 // a file must have been deleted manually!
497 return null;
498 }
499
500 redundantOpCount++;
501 journalWriter.append(READ + ' ' + key + '\n');
502 if (journalRebuildRequired()) {
503 executorService.submit(cleanupCallable);
504 }
505
506 return new Snapshot(key, entry.sequenceNumber, ins);
507 }
508
509 /**
510 * Returns an editor for the entry named {@code key}, or null if another
511 * edit is in progress.
512 */
513 public Editor edit(String key) throws IOException {
514 return edit(key, ANY_SEQUENCE_NUMBER);
515 }
516
517 private synchronized Editor edit(String key, long expectedSequenceNumber) throws IOException {
518 checkNotClosed();
519 validateKey(key);
520 Entry entry = lruEntries.get(key);
521 if (expectedSequenceNumber != ANY_SEQUENCE_NUMBER
522 && (entry == null || entry.sequenceNumber != expectedSequenceNumber)) {
523 return null; // snapshot is stale
524 }
525 if (entry == null) {
526 entry = new Entry(key);
527 lruEntries.put(key, entry);
528 } else if (entry.currentEditor != null) {
529 return null; // another edit is in progress
530 }
531
532 Editor editor = new Editor(entry);
533 entry.currentEditor = editor;
534
535 // flush the journal before creating files to prevent file leaks
536 journalWriter.write(DIRTY + ' ' + key + '\n');
537 journalWriter.flush();
538 return editor;
539 }
540
541 /**
542 * Returns the directory where this cache stores its data.
543 */
544 public File getDirectory() {
545 return directory;
546 }
547
548 /**
549 * Returns the maximum number of bytes that this cache should use to store
550 * its data.
551 */
552 public long maxSize() {
553 return maxSize;
554 }
555
556 /**
557 * Returns the number of bytes currently being used to store the values in
558 * this cache. This may be greater than the max size if a background
559 * deletion is pending.
560 */
561 public synchronized long size() {
562 return size;
563 }
564
565 private synchronized void completeEdit(Editor editor, boolean success) throws IOException {
566 Entry entry = editor.entry;
567 if (entry.currentEditor != editor) {
568 throw new IllegalStateException();
569 }
570
571 // if this edit is creating the entry for the first time, every index must have a value
572 if (success && !entry.readable) {
573 for (int i = 0; i < valueCount; i++) {
574 if (!entry.getDirtyFile(i).exists()) {
575 editor.abort();
576 throw new IllegalStateException("edit didn't create file " + i);
577 }
578 }
579 }
580
581 for (int i = 0; i < valueCount; i++) {
582 File dirty = entry.getDirtyFile(i);
583 if (success) {
584 if (dirty.exists()) {
585 File clean = entry.getCleanFile(i);
586 dirty.renameTo(clean);
587 long oldLength = entry.lengths[i];
588 long newLength = clean.length();
589 entry.lengths[i] = newLength;
590 size = size - oldLength + newLength;
591 }
592 } else {
593 deleteIfExists(dirty);
594 }
595 }
596
597 redundantOpCount++;
598 entry.currentEditor = null;
599 if (entry.readable | success) {
600 entry.readable = true;
601 journalWriter.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n');
602 if (success) {
603 entry.sequenceNumber = nextSequenceNumber++;
604 }
605 } else {
606 lruEntries.remove(entry.key);
607 journalWriter.write(REMOVE + ' ' + entry.key + '\n');
608 }
609
610 if (size > maxSize || journalRebuildRequired()) {
611 executorService.submit(cleanupCallable);
612 }
613 }
614
615 /**
616 * We only rebuild the journal when it will halve the size of the journal
617 * and eliminate at least 2000 ops.
618 */
619 private boolean journalRebuildRequired() {
620 final int REDUNDANT_OP_COMPACT_THRESHOLD = 2000;
621 return redundantOpCount >= REDUNDANT_OP_COMPACT_THRESHOLD
622 && redundantOpCount >= lruEntries.size();
623 }
624
625 /**
626 * Drops the entry for {@code key} if it exists and can be removed. Entries
627 * actively being edited cannot be removed.
628 *
629 * @return true if an entry was removed.
630 */
631 public synchronized boolean remove(String key) throws IOException {
632 checkNotClosed();
633 validateKey(key);
634 Entry entry = lruEntries.get(key);
635 if (entry == null || entry.currentEditor != null) {
636 return false;
637 }
638
639 for (int i = 0; i < valueCount; i++) {
640 File file = entry.getCleanFile(i);
641 if (!file.delete()) {
642 throw new IOException("failed to delete " + file);
643 }
644 size -= entry.lengths[i];
645 entry.lengths[i] = 0;
646 }
647
648 redundantOpCount++;
649 journalWriter.append(REMOVE + ' ' + key + '\n');
650 lruEntries.remove(key);
651
652 if (journalRebuildRequired()) {
653 executorService.submit(cleanupCallable);
654 }
655
656 return true;
657 }
658
659 /**
660 * Returns true if this cache has been closed.
661 */
662 public boolean isClosed() {
663 return journalWriter == null;
664 }
665
666 private void checkNotClosed() {
667 if (journalWriter == null) {
668 throw new IllegalStateException("cache is closed");
669 }
670 }
671
672 /**
673 * Force buffered operations to the filesystem.
674 */
675 public synchronized void flush() throws IOException {
676 checkNotClosed();
677 trimToSize();
678 journalWriter.flush();
679 }
680
681 /**
682 * Closes this cache. Stored values will remain on the filesystem.
683 */
684 public synchronized void close() throws IOException {
685 if (journalWriter == null) {
686 return; // already closed
687 }
688 for (Entry entry : new ArrayList<Entry>(lruEntries.values())) {
689 if (entry.currentEditor != null) {
690 entry.currentEditor.abort();
691 }
692 }
693 trimToSize();
694 journalWriter.close();
695 journalWriter = null;
696 }
697
698 private void trimToSize() throws IOException {
699 while (size > maxSize) {
700 // Map.Entry<String, Entry> toEvict = lruEntries.eldest();
701 final Map.Entry<String, Entry> toEvict = lruEntries.entrySet().iterator().next();
702 remove(toEvict.getKey());
703 }
704 }
705
706 /**
707 * Closes the cache and deletes all of its stored values. This will delete
708 * all files in the cache directory including files that weren't created by
709 * the cache.
710 */
711 public void delete() throws IOException {
712 close();
713 deleteContents(directory);
714 }
715
716 private void validateKey(String key) {
717 if (key.contains(" ") || key.contains("\n") || key.contains("\r")) {
718 throw new IllegalArgumentException(
719 "keys must not contain spaces or newlines: \"" + key + "\"");
720 }
721 }
722
723 private static String inputStreamToString(InputStream in) throws IOException {
724 return readFully(new InputStreamReader(in, UTF_8));
725 }
726
727 /**
728 * A snapshot of the values for an entry.
729 */
730 public final class Snapshot implements Closeable {
731 private final String key;
732 private final long sequenceNumber;
733 private final InputStream[] ins;
734
735 private Snapshot(String key, long sequenceNumber, InputStream[] ins) {
736 this.key = key;
737 this.sequenceNumber = sequenceNumber;
738 this.ins = ins;
739 }
740
741 /**
742 * Returns an editor for this snapshot's entry, or null if either the
743 * entry has changed since this snapshot was created or if another edit
744 * is in progress.
745 */
746 public Editor edit() throws IOException {
747 return DiskLruCache.this.edit(key, sequenceNumber);
748 }
749
750 /**
751 * Returns the unbuffered stream with the value for {@code index}.
752 */
753 public InputStream getInputStream(int index) {
754 return ins[index];
755 }
756
757 /**
758 * Returns the string value for {@code index}.
759 */
760 public String getString(int index) throws IOException {
761 return inputStreamToString(getInputStream(index));
762 }
763
764 @Override public void close() {
765 for (InputStream in : ins) {
766 closeQuietly(in);
767 }
768 }
769 }
770
771 /**
772 * Edits the values for an entry.
773 */
774 public final class Editor {
775 private final Entry entry;
776 private boolean hasErrors;
777
778 private Editor(Entry entry) {
779 this.entry = entry;
780 }
781
782 /**
783 * Returns an unbuffered input stream to read the last committed value,
784 * or null if no value has been committed.
785 */
786 public InputStream newInputStream(int index) throws IOException {
787 synchronized (DiskLruCache.this) {
788 if (entry.currentEditor != this) {
789 throw new IllegalStateException();
790 }
791 if (!entry.readable) {
792 return null;
793 }
794 return new FileInputStream(entry.getCleanFile(index));
795 }
796 }
797
798 /**
799 * Returns the last committed value as a string, or null if no value
800 * has been committed.
801 */
802 public String getString(int index) throws IOException {
803 InputStream in = newInputStream(index);
804 return in != null ? inputStreamToString(in) : null;
805 }
806
807 /**
808 * Returns a new unbuffered output stream to write the value at
809 * {@code index}. If the underlying output stream encounters errors
810 * when writing to the filesystem, this edit will be aborted when
811 * {@link #commit} is called. The returned output stream does not throw
812 * IOExceptions.
813 */
814 public OutputStream newOutputStream(int index) throws IOException {
815 synchronized (DiskLruCache.this) {
816 if (entry.currentEditor != this) {
817 throw new IllegalStateException();
818 }
819 return new FaultHidingOutputStream(new FileOutputStream(entry.getDirtyFile(index)));
820 }
821 }
822
823 /**
824 * Sets the value at {@code index} to {@code value}.
825 */
826 public void set(int index, String value) throws IOException {
827 Writer writer = null;
828 try {
829 writer = new OutputStreamWriter(newOutputStream(index), UTF_8);
830 writer.write(value);
831 } finally {
832 closeQuietly(writer);
833 }
834 }
835
836 /**
837 * Commits this edit so it is visible to readers. This releases the
838 * edit lock so another edit may be started on the same key.
839 */
840 public void commit() throws IOException {
841 if (hasErrors) {
842 completeEdit(this, false);
843 remove(entry.key); // the previous entry is stale
844 } else {
845 completeEdit(this, true);
846 }
847 }
848
849 /**
850 * Aborts this edit. This releases the edit lock so another edit may be
851 * started on the same key.
852 */
853 public void abort() throws IOException {
854 completeEdit(this, false);
855 }
856
857 private class FaultHidingOutputStream extends FilterOutputStream {
858 private FaultHidingOutputStream(OutputStream out) {
859 super(out);
860 }
861
862 @Override public void write(int oneByte) {
863 try {
864 out.write(oneByte);
865 } catch (IOException e) {
866 hasErrors = true;
867 }
868 }
869
870 @Override public void write(byte[] buffer, int offset, int length) {
871 try {
872 out.write(buffer, offset, length);
873 } catch (IOException e) {
874 hasErrors = true;
875 }
876 }
877
878 @Override public void close() {
879 try {
880 out.close();
881 } catch (IOException e) {
882 hasErrors = true;
883 }
884 }
885
886 @Override public void flush() {
887 try {
888 out.flush();
889 } catch (IOException e) {
890 hasErrors = true;
891 }
892 }
893 }
894 }
895
896 private final class Entry {
897 private final String key;
898
899 /** Lengths of this entry's files. */
900 private final long[] lengths;
901
902 /** True if this entry has ever been published */
903 private boolean readable;
904
905 /** The ongoing edit or null if this entry is not being edited. */
906 private Editor currentEditor;
907
908 /** The sequence number of the most recently committed edit to this entry. */
909 private long sequenceNumber;
910
911 private Entry(String key) {
912 this.key = key;
913 this.lengths = new long[valueCount];
914 }
915
916 public String getLengths() throws IOException {
917 StringBuilder result = new StringBuilder();
918 for (long size : lengths) {
919 result.append(' ').append(size);
920 }
921 return result.toString();
922 }
923
924 /**
925 * Set lengths using decimal numbers like "10123".
926 */
927 private void setLengths(String[] strings) throws IOException {
928 if (strings.length != valueCount) {
929 throw invalidLengths(strings);
930 }
931
932 try {
933 for (int i = 0; i < strings.length; i++) {
934 lengths[i] = Long.parseLong(strings[i]);
935 }
936 } catch (NumberFormatException e) {
937 throw invalidLengths(strings);
938 }
939 }
940
941 private IOException invalidLengths(String[] strings) throws IOException {
942 throw new IOException("unexpected journal line: " + Arrays.toString(strings));
943 }
944
945 public File getCleanFile(int i) {
946 return new File(directory, key + "." + i);
947 }
948
949 public File getDirtyFile(int i) {
950 return new File(directory, key + "." + i + ".tmp");
951 }
952 }
953 }
