summaryrefslogtreecommitdiffstats
path: root/gallerycommon/src/com/android/gallery3d/exif/ExifParser.java
blob: 56f722afbe38bf47c2ed193ce1e3211d87d875d5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.gallery3d.exif;

import java.io.DataInputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteOrder;
import java.nio.charset.Charset;
import java.util.Map.Entry;
import java.util.TreeMap;

/**
 * This class provides a low-level EXIF parsing API. Given a JPEG format InputStream, the caller
 * can request which IFD's to read via {@link #parse(InputStream, int)} with given options.
 * <p>
 * Below is an example of getting EXIF data from IFD 0 and EXIF IFD using the parser.
 * <pre>
 * void parse() {
 *     ExifParser parser = ExifParser.parse(mImageInputStream,
 *             ExifParser.OPTION_IFD_0 | ExifParser.OPTIONS_IFD_EXIF);
 *     int event = parser.next();
 *     while (event != ExifParser.EVENT_END) {
 *         switch (event) {
 *             case ExifParser.EVENT_START_OF_IFD:
 *                 break;
 *             case ExifParser.EVENT_NEW_TAG:
 *                 ExifTag tag = parser.getTag();
 *                 if (!tag.hasValue()) {
 *                     parser.registerForTagValue(tag);
 *                 } else {
 *                     processTag(tag);
 *                 }
 *                 break;
 *             case ExifParser.EVENT_VALUE_OF_REGISTERED_TAG:
 *                 tag = parser.getTag();
 *                 if (tag.getDataType() != ExifTag.TYPE_UNDEFINED) {
 *                     processTag(tag);
 *                 }
 *                 break;
 *         }
 *         event = parser.next();
 *     }
 * }
 *
 * void processTag(ExifTag tag) {
 *     // process the tag as you like.
 * }
 * </pre>
 */
public class ExifParser {
    /**
     * When the parser reaches a new IFD area. Call
     *  {@link #getCurrentIfd()} to know which IFD we are in.
     */
    public static final int EVENT_START_OF_IFD = 0;
    /**
     * When the parser reaches a new tag. Call {@link #getTag()}to get the
     * corresponding tag.
     */
    public static final int EVENT_NEW_TAG = 1;
    /**
     * When the parser reaches the value area of tag that is registered by
     *  {@link #registerForTagValue(ExifTag)} previously. Call
     *  {@link #getTag()} to get the corresponding tag.
     */
    public static final int EVENT_VALUE_OF_REGISTERED_TAG = 2;

    /**
     * When the parser reaches the compressed image area.
     */
    public static final int EVENT_COMPRESSED_IMAGE = 3;
    /**
     * When the parser reaches the uncompressed image strip.
     *  Call {@link #getStripIndex()} to get the index of the strip.
     * @see #getStripIndex()
     * @see #getStripCount()
     */
    public static final int EVENT_UNCOMPRESSED_STRIP = 4;
    /**
     * When there is nothing more to parse.
     */
    public static final int EVENT_END = 5;

    /**
     * Option bit to request to parse IFD0.
     */
    public static final int OPTION_IFD_0 = 1 << 0;
    /**
     * Option bit to request to parse IFD1.
     */
    public static final int OPTION_IFD_1 = 1 << 1;
    /**
     * Option bit to request to parse Exif-IFD.
     */
    public static final int OPTION_IFD_EXIF = 1 << 2;
    /**
     * Option bit to request to parse GPS-IFD.
     */
    public static final int OPTION_IFD_GPS = 1 << 3;
    /**
     * Option bit to request to parse Interoperability-IFD.
     */
    public static final int OPTION_IFD_INTEROPERABILITY = 1 << 4;
    /**
     * Option bit to request to parse thumbnail.
     */
    public static final int OPTION_THUMBNAIL = 1 << 5;

    private static final int EXIF_HEADER = 0x45786966; // EXIF header "Exif"
    private static final short EXIF_HEADER_TAIL = (short) 0x0000; // EXIF header in APP1

    // TIFF header
    private static final short LITTLE_ENDIAN_TAG = (short) 0x4949; // "II"
    private static final short BIG_ENDIAN_TAG = (short) 0x4d4d; // "MM"
    private static final short TIFF_HEADER_TAIL = 0x002A;

    private static final int TAG_SIZE = 12;
    private static final int OFFSET_SIZE = 2;

    private final CountedDataInputStream mTiffStream;
    private final int mOptions;
    private int mIfdStartOffset = 0;
    private int mNumOfTagInIfd = 0;
    private int mIfdType;
    private ExifTag mTag;
    private ImageEvent mImageEvent;
    private int mStripCount;
    private ExifTag mStripSizeTag;
    private ExifTag mJpegSizeTag;
    private boolean mNeedToParseOffsetsInCurrentIfd;
    private boolean mContainExifData = false;

    private final TreeMap<Integer, Object> mCorrespondingEvent = new TreeMap<Integer, Object>();

    private boolean isIfdRequested(int ifdType) {
        switch (ifdType) {
            case IfdId.TYPE_IFD_0:
                return (mOptions & OPTION_IFD_0) != 0;
            case IfdId.TYPE_IFD_1:
                return (mOptions & OPTION_IFD_1) != 0;
            case IfdId.TYPE_IFD_EXIF:
                return (mOptions & OPTION_IFD_EXIF) != 0;
            case IfdId.TYPE_IFD_GPS:
                return (mOptions & OPTION_IFD_GPS) != 0;
            case IfdId.TYPE_IFD_INTEROPERABILITY:
                return (mOptions & OPTION_IFD_INTEROPERABILITY) != 0;
        }
        return false;
    }

    private boolean isThumbnailRequested() {
        return (mOptions & OPTION_THUMBNAIL) != 0;
    }

    private ExifParser(InputStream inputStream, int options)
            throws IOException, ExifInvalidFormatException {
        mContainExifData = seekTiffData(inputStream);
        mTiffStream = new CountedDataInputStream(inputStream);
        mOptions = options;
        if (!mContainExifData) return;
        if (mTiffStream.getReadByteCount() == 0) {
            parseTiffHeader();
            long offset = mTiffStream.readUnsignedInt();
            registerIfd(IfdId.TYPE_IFD_0, offset);
        }
    }

    /**
     * Parses the the given InputStream with the given options
     * @exception IOException
     * @exception ExifInvalidFormatException
     */
    public static ExifParser parse(InputStream inputStream, int options)
             throws IOException, ExifInvalidFormatException {
         return new ExifParser(inputStream, options);
    }

    /**
     * Parses the the given InputStream with default options; that is, every IFD and thumbnaill
     * will be parsed.
     * @exception IOException
     * @exception ExifInvalidFormatException
     * @see #parse(InputStream, int)
     */
    public static ExifParser parse(InputStream inputStream)
            throws IOException, ExifInvalidFormatException {
        return new ExifParser(inputStream, OPTION_IFD_0 | OPTION_IFD_1
                | OPTION_IFD_EXIF | OPTION_IFD_GPS | OPTION_IFD_INTEROPERABILITY
                | OPTION_THUMBNAIL);
    }

    /**
     * Moves the parser forward and returns the next parsing event
     *
     * @exception IOException
     * @exception ExifInvalidFormatException
     * @see #EVENT_START_OF_IFD
     * @see #EVENT_NEW_TAG
     * @see #EVENT_VALUE_OF_REGISTERED_TAG
     * @see #EVENT_COMPRESSED_IMAGE
     * @see #EVENT_UNCOMPRESSED_STRIP
     * @see #EVENT_END
     */
    public int next() throws IOException, ExifInvalidFormatException {
        if (!mContainExifData) {
            return EVENT_END;
        }
        int offset = mTiffStream.getReadByteCount();
        int endOfTags = mIfdStartOffset + OFFSET_SIZE + TAG_SIZE * mNumOfTagInIfd;
        if (offset < endOfTags) {
            mTag = readTag();
            if (mNeedToParseOffsetsInCurrentIfd) {
                checkOffsetOrImageTag(mTag);
            }
            return EVENT_NEW_TAG;
        } else if (offset == endOfTags) {
            long ifdOffset = readUnsignedLong();
            // There is a link to ifd1 at the end of ifd0
            if (mIfdType == IfdId.TYPE_IFD_0) {
                if (isIfdRequested(IfdId.TYPE_IFD_1) || isThumbnailRequested()) {
                    if (ifdOffset != 0) {
                        registerIfd(IfdId.TYPE_IFD_1, ifdOffset);
                    }
                }
            } else {
                if (ifdOffset != 0) {
                    throw new ExifInvalidFormatException("Invalid link to next IFD");
                }
            }
        }
        while(mCorrespondingEvent.size() != 0) {
            Entry<Integer, Object> entry = mCorrespondingEvent.pollFirstEntry();
            Object event = entry.getValue();
            skipTo(entry.getKey());
            if (event instanceof IfdEvent) {
                mIfdType = ((IfdEvent) event).ifd;
                mNumOfTagInIfd = mTiffStream.readUnsignedShort();
                mIfdStartOffset = entry.getKey();
                mNeedToParseOffsetsInCurrentIfd = needToParseOffsetsInCurrentIfd();
                if (((IfdEvent) event).isRequested) {
                    return EVENT_START_OF_IFD;
                } else {
                    skipRemainingTagsInCurrentIfd();
                }
            } else if (event instanceof ImageEvent) {
                mImageEvent = (ImageEvent) event;
                return mImageEvent.type;
            } else {
                ExifTagEvent tagEvent = (ExifTagEvent) event;
                mTag = tagEvent.tag;
                if (mTag.getDataType() != ExifTag.TYPE_UNDEFINED) {
                    readFullTagValue(mTag);
                    checkOffsetOrImageTag(mTag);
                }
                if (tagEvent.isRequested) {
                    return EVENT_VALUE_OF_REGISTERED_TAG;
                }
            }
        }
        return EVENT_END;
    }

    /**
     * Skips the tags area of current IFD, if the parser is not in the tag area, nothing will
     * happen.
     *
     * @throws IOException
     * @throws ExifInvalidFormatException
     */
    public void skipRemainingTagsInCurrentIfd() throws IOException, ExifInvalidFormatException {
        int endOfTags = mIfdStartOffset + OFFSET_SIZE + TAG_SIZE * mNumOfTagInIfd;
        int offset = mTiffStream.getReadByteCount();
        if (offset > endOfTags) return;
        if (mNeedToParseOffsetsInCurrentIfd) {
            while (offset < endOfTags) {
                mTag = readTag();
                checkOffsetOrImageTag(mTag);
                offset += TAG_SIZE;
            }
        } else {
            skipTo(endOfTags);
        }
        long ifdOffset = readUnsignedLong();
        // For ifd0, there is a link to ifd1 in the end of all tags
        if (mIfdType == IfdId.TYPE_IFD_0
                && (isIfdRequested(IfdId.TYPE_IFD_1) || isThumbnailRequested())) {
            if (ifdOffset > 0) {
                registerIfd(IfdId.TYPE_IFD_1, ifdOffset);
            }
        }
    }

    private boolean needToParseOffsetsInCurrentIfd() {
        switch (mIfdType) {
            case IfdId.TYPE_IFD_0:
                return isIfdRequested(IfdId.TYPE_IFD_EXIF) || isIfdRequested(IfdId.TYPE_IFD_GPS)
                        || isIfdRequested(IfdId.TYPE_IFD_INTEROPERABILITY);
            case IfdId.TYPE_IFD_1:
                return isThumbnailRequested();
            case IfdId.TYPE_IFD_EXIF:
                // The offset to interoperability IFD is located in Exif IFD
                return isIfdRequested(IfdId.TYPE_IFD_INTEROPERABILITY);
            default:
                return false;
        }
    }

    /**
     * If {@link #next()} return {@link #EVENT_NEW_TAG} or {@link #EVENT_VALUE_OF_REGISTERED_TAG},
     * call this function to get the corresponding tag.
     * <p>
     *
     * For {@link #EVENT_NEW_TAG}, the tag may not contain the value if the size of the value is
     * greater than 4 bytes. One should call {@link ExifTag#hasValue()} to check if the tag
     * contains value.
     * If there is no value,call {@link #registerForTagValue(ExifTag)} to have the parser emit
     * {@link #EVENT_VALUE_OF_REGISTERED_TAG} when it reaches the area pointed by the offset.
     *
     * <p>
     * When {@link #EVENT_VALUE_OF_REGISTERED_TAG} is emitted, the value of the tag will have
     * already been read except for tags of undefined type. For tags of undefined type, call
     * one of the read methods to get the value.
     *
     * @see #registerForTagValue(ExifTag)
     * @see #read(byte[])
     * @see #read(byte[], int, int)
     * @see #readLong()
     * @see #readRational()
     * @see #readShort()
     * @see #readString(int)
     * @see #readString(int, Charset)
     */
    public ExifTag getTag() {
        return mTag;
    }

    /**
     * Gets number of tags in the current IFD area.
     */
    public int getTagCountInCurrentIfd() {
        return mNumOfTagInIfd;
    }

    /**
     * Gets the ID of current IFD.
     *
     * @see IfdId#TYPE_IFD_0
     * @see IfdId#TYPE_IFD_1
     * @see IfdId#TYPE_IFD_GPS
     * @see IfdId#TYPE_IFD_INTEROPERABILITY
     * @see IfdId#TYPE_IFD_EXIF
     */
    public int getCurrentIfd() {
        return mIfdType;
    }

    /**
     * When receiving {@link #EVENT_UNCOMPRESSED_STRIP},
     * call this function to get the index of this strip.
     * @see #getStripCount()
     */
    public int getStripIndex() {
        return mImageEvent.stripIndex;
    }

    /**
     * When receiving {@link #EVENT_UNCOMPRESSED_STRIP}, call this function to get the number
     * of strip data.
     * @see #getStripIndex()
     */
    public int getStripCount() {
        return mStripCount;
    }

    /**
     * When receiving {@link #EVENT_UNCOMPRESSED_STRIP}, call this function to get the strip size.
     */
    public int getStripSize() {
        if (mStripSizeTag == null) return 0;
        if (mStripSizeTag.getDataType() == ExifTag.TYPE_UNSIGNED_SHORT) {
            return mStripSizeTag.getUnsignedShort(mImageEvent.stripIndex);
        } else {
            // Cast unsigned int to int since the strip size is always smaller
            // than the size of APP1 (65536)
            return (int) mStripSizeTag.getUnsignedLong(mImageEvent.stripIndex);
        }
    }

    /**
     * When receiving {@link #EVENT_COMPRESSED_IMAGE}, call this function to get the image data
     * size.
     */
    public int getCompressedImageSize() {
        if (mJpegSizeTag == null) return 0;
        // Cast unsigned int to int since the thumbnail is always smaller
        // than the size of APP1 (65536)
        return (int) mJpegSizeTag.getUnsignedLong(0);
    }

    private void skipTo(int offset) throws IOException {
        mTiffStream.skipTo(offset);
        while (!mCorrespondingEvent.isEmpty() && mCorrespondingEvent.firstKey() < offset) {
            mCorrespondingEvent.pollFirstEntry();
        }
    }

    /**
     * When getting {@link #EVENT_NEW_TAG} in the tag area of IFD,
     * the tag may not contain the value if the size of the value is greater than 4 bytes.
     * When the value is not available here, call this method so that the parser will emit
     * {@link #EVENT_VALUE_OF_REGISTERED_TAG} when it reaches the area where the value is located.

     * @see #EVENT_VALUE_OF_REGISTERED_TAG
     */
    public void registerForTagValue(ExifTag tag) {
        mCorrespondingEvent.put(tag.getOffset(), new ExifTagEvent(tag, true));
    }

    private void registerIfd(int ifdType, long offset) {
        // Cast unsigned int to int since the offset is always smaller
        // than the size of APP1 (65536)
        mCorrespondingEvent.put((int) offset, new IfdEvent(ifdType, isIfdRequested(ifdType)));
    }

    private void registerCompressedImage(long offset) {
        mCorrespondingEvent.put((int) offset, new ImageEvent(EVENT_COMPRESSED_IMAGE));
    }

    private void registerUncompressedStrip(int stripIndex, long offset) {
        mCorrespondingEvent.put((int) offset, new ImageEvent(EVENT_UNCOMPRESSED_STRIP
                , stripIndex));
    }

    private ExifTag readTag() throws IOException, ExifInvalidFormatException {
        short tagId = mTiffStream.readShort();
        short dataFormat = mTiffStream.readShort();
        long numOfComp = mTiffStream.readUnsignedInt();
        if (numOfComp > Integer.MAX_VALUE) {
            throw new ExifInvalidFormatException(
                    "Number of component is larger then Integer.MAX_VALUE");
        }
        ExifTag tag = new ExifTag(tagId, dataFormat, (int) numOfComp, mIfdType);
        int dataSize = tag.getDataSize();
        if (dataSize > 4) {
            long offset = mTiffStream.readUnsignedInt();
            if (offset > Integer.MAX_VALUE) {
                throw new ExifInvalidFormatException(
                        "offset is larger then Integer.MAX_VALUE");
            }
            tag.setOffset((int) offset);
        } else {
            readFullTagValue(tag);
            mTiffStream.skip(4 - dataSize);
        }
        return tag;
    }

    /**
     * Check the tag, if the tag is one of the offset tag that points to the IFD or image the
     * caller is interested in, register the IFD or image.
     */
    private void checkOffsetOrImageTag(ExifTag tag) {
        switch (tag.getTagId()) {
            case ExifTag.TAG_EXIF_IFD:
                if (isIfdRequested(IfdId.TYPE_IFD_EXIF)
                        || isIfdRequested(IfdId.TYPE_IFD_INTEROPERABILITY)) {
                    registerIfd(IfdId.TYPE_IFD_EXIF, tag.getUnsignedLong(0));
                }
                break;
            case ExifTag.TAG_GPS_IFD:
                if (isIfdRequested(IfdId.TYPE_IFD_GPS)) {
                    registerIfd(IfdId.TYPE_IFD_GPS, tag.getUnsignedLong(0));
                }
                break;
            case ExifTag.TAG_INTEROPERABILITY_IFD:
                if (isIfdRequested(IfdId.TYPE_IFD_INTEROPERABILITY)) {
                    registerIfd(IfdId.TYPE_IFD_INTEROPERABILITY, tag.getUnsignedLong(0));
                }
                break;
            case ExifTag.TAG_JPEG_INTERCHANGE_FORMAT:
                if (isThumbnailRequested()) {
                    registerCompressedImage(tag.getUnsignedLong(0));
                }
                break;
            case ExifTag.TAG_JPEG_INTERCHANGE_FORMAT_LENGTH:
                if (isThumbnailRequested()) {
                    mJpegSizeTag = tag;
                }
                break;
            case ExifTag.TAG_STRIP_OFFSETS:
                if (isThumbnailRequested()) {
                    if (tag.hasValue()) {
                        for (int i = 0; i < tag.getComponentCount(); i++) {
                            if (tag.getDataType() == ExifTag.TYPE_UNSIGNED_SHORT) {
                                registerUncompressedStrip(i, tag.getUnsignedShort(i));
                            } else {
                                registerUncompressedStrip(i, tag.getUnsignedLong(i));
                            }
                        }
                    } else {
                        mCorrespondingEvent.put(tag.getOffset(), new ExifTagEvent(tag, false));
                    }
                }
                break;
            case ExifTag.TAG_STRIP_BYTE_COUNTS:
                if (isThumbnailRequested()) {
                    if (tag.hasValue()) {
                        mStripSizeTag = tag;
                    }
                }
                break;
        }
    }

    private void readFullTagValue(ExifTag tag) throws IOException {
        switch(tag.getDataType()) {
            case ExifTag.TYPE_UNSIGNED_BYTE:
            case ExifTag.TYPE_UNDEFINED:
                {
                    byte buf[] = new byte[tag.getComponentCount()];
                    read(buf);
                    tag.setValue(buf);
                }
                break;
            case ExifTag.TYPE_ASCII:
                tag.setValue(readString(tag.getComponentCount()));
                break;
            case ExifTag.TYPE_UNSIGNED_LONG:
                {
                    long value[] = new long[tag.getComponentCount()];
                    for (int i = 0, n = value.length; i < n; i++) {
                        value[i] = readUnsignedLong();
                    }
                    tag.setValue(value);
                }
                break;
          case ExifTag.TYPE_UNSIGNED_RATIONAL:
              {
                  Rational value[] = new Rational[tag.getComponentCount()];
                  for (int i = 0, n = value.length; i < n; i++) {
                      value[i] = readUnsignedRational();
                  }
                  tag.setValue(value);
              }
              break;
          case ExifTag.TYPE_UNSIGNED_SHORT:
              {
                  int value[] = new int[tag.getComponentCount()];
                  for (int i = 0, n = value.length; i < n; i++) {
                      value[i] = readUnsignedShort();
                  }
                  tag.setValue(value);
              }
              break;
          case ExifTag.TYPE_LONG:
              {
                  int value[] = new int[tag.getComponentCount()];
                  for (int i = 0, n = value.length; i < n; i++) {
                      value[i] = readLong();
                  }
                  tag.setValue(value);
              }
              break;
          case ExifTag.TYPE_RATIONAL:
              {
                  Rational value[] = new Rational[tag.getComponentCount()];
                  for (int i = 0, n = value.length; i < n; i++) {
                      value[i] = readRational();
                  }
                  tag.setValue(value);
              }
              break;
        }
    }

    private void parseTiffHeader() throws IOException,
            ExifInvalidFormatException {
        short byteOrder = mTiffStream.readShort();
        ByteOrder order;
        if (LITTLE_ENDIAN_TAG == byteOrder) {
            mTiffStream.setByteOrder(ByteOrder.LITTLE_ENDIAN);
        } else if (BIG_ENDIAN_TAG == byteOrder) {
            mTiffStream.setByteOrder(ByteOrder.BIG_ENDIAN);
        } else {
            throw new ExifInvalidFormatException("Invalid TIFF header");
        }

        if (mTiffStream.readShort() != TIFF_HEADER_TAIL) {
            throw new ExifInvalidFormatException("Invalid TIFF header");
        }
    }

    private boolean seekTiffData(InputStream inputStream) throws IOException,
            ExifInvalidFormatException {
        DataInputStream dataStream = new DataInputStream(inputStream);

        // SOI and APP1
        if (dataStream.readShort() != JpegHeader.SOI) {
            throw new ExifInvalidFormatException("Invalid JPEG format");
        }

        short marker = dataStream.readShort();
        while(marker != JpegHeader.APP1 && marker != JpegHeader.EOI
                && !JpegHeader.isSofMarker(marker)) {
            int length = dataStream.readUnsignedShort();
            if ((length - 2) != dataStream.skip(length - 2)) {
                throw new EOFException();
            }
            marker = dataStream.readShort();
        }

        if (marker != JpegHeader.APP1) return false; // No APP1 segment

        // APP1 length, it's not used for us
        dataStream.readShort();

        // Exif header
        return (dataStream.readInt() == EXIF_HEADER
                && dataStream.readShort() == EXIF_HEADER_TAIL);
    }

    /**
     * Reads bytes from the InputStream.
     */
    public int read(byte[] buffer, int offset, int length) throws IOException {
        return mTiffStream.read(buffer, offset, length);
    }

    /**
     * Equivalent to read(buffer, 0, buffer.length).
     */
    public int read(byte[] buffer) throws IOException {
        return mTiffStream.read(buffer);
    }

    /**
     * Reads a String from the InputStream with US-ASCII charset.
     * This is used for reading values of type {@link ExifTag#TYPE_ASCII}.
     */
    public String readString(int n) throws IOException {
        if (n > 0) {
            byte[] buf = new byte[n];
            mTiffStream.readOrThrow(buf);
            return new String(buf, 0, n - 1, "US-ASCII");
        } else {
            return "";
        }
    }

    /**
     * Reads a String from the InputStream with the given charset.
     * This is used for reading values of type {@link ExifTag#TYPE_ASCII}.
     */
    public String readString(int n, Charset charset) throws IOException {
        byte[] buf = new byte[n];
        mTiffStream.readOrThrow(buf);
        return new String(buf, 0, n - 1, charset);
    }

    /**
     * Reads value of type {@link ExifTag#TYPE_UNSIGNED_SHORT} from the InputStream.
     */
    public int readUnsignedShort() throws IOException {
        return mTiffStream.readShort() & 0xffff;
    }

    /**
     * Reads value of type {@link ExifTag#TYPE_UNSIGNED_LONG} from the InputStream.
     */
    public long readUnsignedLong() throws IOException {
        return readLong() & 0xffffffffL;
    }

    /**
     * Reads value of type {@link ExifTag#TYPE_UNSIGNED_RATIONAL} from the InputStream.
     */
    public Rational readUnsignedRational() throws IOException {
        long nomi = readUnsignedLong();
        long denomi = readUnsignedLong();
        return new Rational(nomi, denomi);
    }

    /**
     * Reads value of type {@link ExifTag#TYPE_LONG} from the InputStream.
     */
    public int readLong() throws IOException {
        return mTiffStream.readInt();
    }

    /**
     * Reads value of type {@link ExifTag#TYPE_RATIONAL} from the InputStream.
     */
    public Rational readRational() throws IOException {
        int nomi = readLong();
        int denomi = readLong();
        return new Rational(nomi, denomi);
    }

    private static class ImageEvent {
        int stripIndex;
        int type;
        ImageEvent(int type) {
            this.stripIndex = 0;
            this.type = type;
        }
        ImageEvent(int type, int stripIndex) {
            this.type = type;
            this.stripIndex = stripIndex;
        }
    }

    private static class IfdEvent {
        int ifd;
        boolean isRequested;
        IfdEvent(int ifd, boolean isInterestedIfd) {
            this.ifd = ifd;
            this.isRequested = isInterestedIfd;
        }
    }

    private static class ExifTagEvent {
        ExifTag tag;
        boolean isRequested;
        ExifTagEvent(ExifTag tag, boolean isRequireByUser) {
            this.tag = tag;
            this.isRequested = isRequireByUser;
        }
    }

    /**
     * Gets the byte order of the current InputStream.
     */
    public ByteOrder getByteOrder() {
        return mTiffStream.getByteOrder();
    }
}