Skip to content

Most visited

Recently visited

navigation
DisplayingBitmaps / src / com.example.android.displayingbitmaps / util /

DiskLruCache.java

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.android.displayingbitmaps.util;
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