1 /*
2 * Copyright 2018 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "include/codec/SkEncodedOrigin.h"
9
10 #include "include/core/SkTypes.h"
11 #include "include/private/base/SkTo.h"
12 #include "src/codec/SkCodecPriv.h"
13
14 #include <algorithm>
15 #include <cstddef>
16 #include <cstdint>
17
parse_encoded_origin(const uint8_t * exifData,size_t data_length,uint64_t offset,bool littleEndian,bool is_root,SkEncodedOrigin * orientation)18 static bool parse_encoded_origin(const uint8_t* exifData, size_t data_length, uint64_t offset,
19 bool littleEndian, bool is_root, SkEncodedOrigin* orientation) {
20 // Require that the marker is at least large enough to contain the number of entries.
21 if (data_length < offset + 2) {
22 return false;
23 }
24 uint32_t numEntries = get_endian_short(exifData + offset, littleEndian);
25
26 // Tag (2 bytes), Datatype (2 bytes), Number of elements (4 bytes), Data (4 bytes)
27 const uint32_t kEntrySize = 12;
28 const auto max = SkTo<uint32_t>((data_length - offset - 2) / kEntrySize);
29 numEntries = std::min(numEntries, max);
30
31 // Advance the data to the start of the entries.
32 auto data = exifData + offset + 2;
33
34 const uint16_t kOriginTag = 0x112;
35 const uint16_t kOriginType = 3;
36 const uint16_t kSubIFDOffsetTag = 0x8769;
37 const uint16_t kSubIFDOffsetType = 4;
38
39 for (uint32_t i = 0; i < numEntries; i++, data += kEntrySize) {
40 uint16_t tag = get_endian_short(data, littleEndian);
41 uint16_t type = get_endian_short(data + 2, littleEndian);
42 uint32_t count = get_endian_int(data + 4, littleEndian);
43
44 if (kOriginTag == tag && kOriginType == type && 1 == count) {
45 uint16_t val = get_endian_short(data + 8, littleEndian);
46 if (0 < val && val <= kLast_SkEncodedOrigin) {
47 *orientation = (SkEncodedOrigin)val;
48 return true;
49 }
50 } else if (kSubIFDOffsetTag == tag && kSubIFDOffsetType == type && 1 == count && is_root) {
51 uint32_t subifd = get_endian_int(data + 8, littleEndian);
52 if (0 < subifd && subifd < data_length) {
53 if (parse_encoded_origin(exifData, data_length, subifd, littleEndian, false,
54 orientation)) {
55 return true;
56 }
57 }
58 }
59 }
60
61 return false;
62 }
63
SkParseEncodedOrigin(const uint8_t * data,size_t data_length,SkEncodedOrigin * orientation)64 bool SkParseEncodedOrigin(const uint8_t* data, size_t data_length, SkEncodedOrigin* orientation) {
65 SkASSERT(orientation);
66 bool littleEndian;
67 // We need eight bytes to read the endian marker and the offset, below.
68 if (data_length < 8 || !is_valid_endian_marker(data, &littleEndian)) {
69 return false;
70 }
71
72 // Get the offset from the start of the marker.
73 // Though this only reads four bytes, use a larger int in case it overflows.
74 uint64_t offset = get_endian_int(data + 4, littleEndian);
75
76 return parse_encoded_origin(data, data_length, offset, littleEndian, true, orientation);
77 }
78