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exif.c
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1 /*
2  * EXIF metadata parser
3  * Copyright (c) 2013 Thilo Borgmann <thilo.borgmann _at_ mail.de>
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /**
23  * @file
24  * EXIF metadata parser
25  * @author Thilo Borgmann <thilo.borgmann _at_ mail.de>
26  */
27 
28 #include "exif.h"
29 
30 
31 static const char *exif_get_tag_name(uint16_t id)
32 {
33  int i;
34 
35  for (i = 0; i < FF_ARRAY_ELEMS(tag_list); i++) {
36  if (tag_list[i].id == id)
37  return tag_list[i].name;
38  }
39 
40  return NULL;
41 }
42 
43 
44 static int exif_add_metadata(AVCodecContext *avctx, int count, int type,
45  const char *name, const char *sep,
46  GetByteContext *gb, int le,
47  AVDictionary **metadata)
48 {
49  switch(type) {
50  case TIFF_DOUBLE : return ff_tadd_doubles_metadata(count, name, sep, gb, le, metadata);
51  case TIFF_SHORT : return ff_tadd_shorts_metadata(count, name, sep, gb, le, metadata);
52  case TIFF_BYTE :
53  case TIFF_UNDEFINED: return ff_tadd_bytes_metadata(count, name, sep, gb, le, metadata);
54  case TIFF_STRING : return ff_tadd_string_metadata(count, name, gb, le, metadata);
55  case TIFF_SRATIONAL:
56  case TIFF_RATIONAL : return ff_tadd_rational_metadata(count, name, sep, gb, le, metadata);
57  case TIFF_SLONG :
58  case TIFF_LONG : return ff_tadd_long_metadata(count, name, sep, gb, le, metadata);
59  default:
60  avpriv_request_sample(avctx, "TIFF tag type (%u)", type);
61  return 0;
62  };
63 }
64 
65 
66 static int exif_decode_tag(AVCodecContext *avctx, GetByteContext *gbytes, int le,
67  int depth, AVDictionary **metadata)
68 {
69  int ret, cur_pos;
70  unsigned id, count;
71  enum TiffTypes type;
72 
73  if (depth > 2) {
74  return 0;
75  }
76 
77  ff_tread_tag(gbytes, le, &id, &type, &count, &cur_pos);
78 
79  // read count values and add it metadata
80  // store metadata or proceed with next IFD
81  ret = ff_tis_ifd(id);
82  if (ret) {
83  ret = ff_exif_decode_ifd(avctx, gbytes, le, depth + 1, metadata);
84  } else {
85  const char *name = exif_get_tag_name(id);
86  char *use_name = (char*) name;
87 
88  if (!use_name) {
89  use_name = av_malloc(7);
90  if (!use_name) {
91  return AVERROR(ENOMEM);
92  }
93  snprintf(use_name, 7, "0x%04X", id);
94  }
95 
96  ret = exif_add_metadata(avctx, count, type, use_name, NULL,
97  gbytes, le, metadata);
98 
99  if (!name) {
100  av_freep(&use_name);
101  }
102  }
103 
104  bytestream2_seek(gbytes, cur_pos, SEEK_SET);
105 
106  return ret;
107 }
108 
109 
111  int depth, AVDictionary **metadata)
112 {
113  int i, ret;
114  int entries;
115 
116  entries = ff_tget_short(gbytes, le);
117 
118  if (bytestream2_get_bytes_left(gbytes) < entries * 12) {
119  return AVERROR_INVALIDDATA;
120  }
121 
122  for (i = 0; i < entries; i++) {
123  if ((ret = exif_decode_tag(avctx, gbytes, le, depth, metadata)) < 0) {
124  return ret;
125  }
126  }
127 
128  // return next IDF offset or 0x000000000 or a value < 0 for failure
129  return ff_tget_long(gbytes, le);
130 }