1 /*
2 * Copyright 2011 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/core/SkStream.h"
9 #include "include/core/SkTypes.h"
10 #include "include/private/base/SkMalloc.h"
11 #include "src/base/SkAutoMalloc.h"
12 #include "src/base/SkEndian.h"
13 #include "src/core/SkFontStream.h"
14
15 #include <cstdint>
16
17 struct SkSFNTHeader {
18 uint32_t fVersion;
19 uint16_t fNumTables;
20 uint16_t fSearchRange;
21 uint16_t fEntrySelector;
22 uint16_t fRangeShift;
23 };
24
25 struct SkTTCFHeader {
26 uint32_t fTag;
27 uint32_t fVersion;
28 uint32_t fNumOffsets;
29 uint32_t fOffset0; // the first of N (fNumOffsets)
30 };
31
32 union SkSharedTTHeader {
33 SkSFNTHeader fSingle;
34 SkTTCFHeader fCollection;
35 };
36
37 struct SkSFNTDirEntry {
38 uint32_t fTag;
39 uint32_t fChecksum;
40 uint32_t fOffset;
41 uint32_t fLength;
42 };
43
read(SkStream * stream,void * buffer,size_t amount)44 static bool read(SkStream* stream, void* buffer, size_t amount) {
45 return stream->read(buffer, amount) == amount;
46 }
47
skip(SkStream * stream,size_t amount)48 static bool skip(SkStream* stream, size_t amount) {
49 return stream->skip(amount) == amount;
50 }
51
52 /** Return the number of tables, or if this is a TTC (collection), return the
53 number of tables in the first element of the collection. In either case,
54 if offsetToDir is not-null, set it to the offset to the beginning of the
55 table headers (SkSFNTDirEntry), relative to the start of the stream.
56
57 On an error, return 0 for number of tables, and ignore offsetToDir
58 */
count_tables(SkStream * stream,int ttcIndex,size_t * offsetToDir)59 static int count_tables(SkStream* stream, int ttcIndex, size_t* offsetToDir) {
60 SkASSERT(ttcIndex >= 0);
61
62 SkAutoSMalloc<1024> storage(sizeof(SkSharedTTHeader));
63 SkSharedTTHeader* header = (SkSharedTTHeader*)storage.get();
64
65 if (!read(stream, header, sizeof(SkSharedTTHeader))) {
66 return 0;
67 }
68
69 // by default, SkSFNTHeader is at the start of the stream
70 size_t offset = 0;
71
72 // if we're really a collection, the first 4-bytes will be 'ttcf'
73 uint32_t tag = SkEndian_SwapBE32(header->fCollection.fTag);
74 if (SkSetFourByteTag('t', 't', 'c', 'f') == tag) {
75 unsigned count = SkEndian_SwapBE32(header->fCollection.fNumOffsets);
76 if ((unsigned)ttcIndex >= count) {
77 return 0;
78 }
79
80 if (ttcIndex > 0) { // need to read more of the shared header
81 stream->rewind();
82 size_t amount = sizeof(SkSharedTTHeader) + ttcIndex * sizeof(uint32_t);
83 header = (SkSharedTTHeader*)storage.reset(amount);
84 if (!read(stream, header, amount)) {
85 return 0;
86 }
87 }
88 // this is the offset to the local SkSFNTHeader
89 offset = SkEndian_SwapBE32((&header->fCollection.fOffset0)[ttcIndex]);
90 stream->rewind();
91 if (!skip(stream, offset)) {
92 return 0;
93 }
94 if (!read(stream, header, sizeof(SkSFNTHeader))) {
95 return 0;
96 }
97 }
98
99 if (offsetToDir) {
100 // add the size of the header, so we will point to the DirEntries
101 *offsetToDir = offset + sizeof(SkSFNTHeader);
102 }
103 return SkEndian_SwapBE16(header->fSingle.fNumTables);
104 }
105
106 ///////////////////////////////////////////////////////////////////////////////
107
108 struct SfntHeader {
SfntHeaderSfntHeader109 SfntHeader() : fCount(0), fDir(nullptr) {}
~SfntHeaderSfntHeader110 ~SfntHeader() { sk_free(fDir); }
111
112 /** If it returns true, then fCount and fDir are properly initialized.
113 Note: fDir will point to the raw array of SkSFNTDirEntry values,
114 meaning they will still be in the file's native endianness (BE).
115
116 fDir will be automatically freed when this object is destroyed
117 */
initSfntHeader118 bool init(SkStream* stream, int ttcIndex) {
119 stream->rewind();
120
121 size_t offsetToDir;
122 fCount = count_tables(stream, ttcIndex, &offsetToDir);
123 if (0 == fCount) {
124 return false;
125 }
126
127 stream->rewind();
128 if (!skip(stream, offsetToDir)) {
129 return false;
130 }
131
132 size_t size = fCount * sizeof(SkSFNTDirEntry);
133 fDir = reinterpret_cast<SkSFNTDirEntry*>(sk_malloc_throw(size));
134 return read(stream, fDir, size);
135 }
136
137 int fCount;
138 SkSFNTDirEntry* fDir;
139 };
140
141 ///////////////////////////////////////////////////////////////////////////////
142
CountTTCEntries(SkStream * stream)143 int SkFontStream::CountTTCEntries(SkStream* stream) {
144 stream->rewind();
145
146 SkSharedTTHeader shared;
147 if (!read(stream, &shared, sizeof(shared))) {
148 return 0;
149 }
150
151 // if we're really a collection, the first 4-bytes will be 'ttcf'
152 uint32_t tag = SkEndian_SwapBE32(shared.fCollection.fTag);
153 if (SkSetFourByteTag('t', 't', 'c', 'f') == tag) {
154 return SkEndian_SwapBE32(shared.fCollection.fNumOffsets);
155 } else {
156 return 1; // normal 'sfnt' has 1 dir entry
157 }
158 }
159
GetTableTags(SkStream * stream,int ttcIndex,SkFontTableTag tags[])160 int SkFontStream::GetTableTags(SkStream* stream, int ttcIndex,
161 SkFontTableTag tags[]) {
162 SfntHeader header;
163 if (!header.init(stream, ttcIndex)) {
164 return 0;
165 }
166
167 if (tags) {
168 for (int i = 0; i < header.fCount; i++) {
169 tags[i] = SkEndian_SwapBE32(header.fDir[i].fTag);
170 }
171 }
172 return header.fCount;
173 }
174
GetTableData(SkStream * stream,int ttcIndex,SkFontTableTag tag,size_t offset,size_t length,void * data)175 size_t SkFontStream::GetTableData(SkStream* stream, int ttcIndex,
176 SkFontTableTag tag,
177 size_t offset, size_t length, void* data) {
178 SfntHeader header;
179 if (!header.init(stream, ttcIndex)) {
180 return 0;
181 }
182
183 for (int i = 0; i < header.fCount; i++) {
184 if (SkEndian_SwapBE32(header.fDir[i].fTag) == tag) {
185 size_t realOffset = SkEndian_SwapBE32(header.fDir[i].fOffset);
186 size_t realLength = SkEndian_SwapBE32(header.fDir[i].fLength);
187 if (offset >= realLength) {
188 // invalid
189 return 0;
190 }
191 // if the caller is trusting the length from the file, then a
192 // hostile file might choose a value which would overflow offset +
193 // length.
194 if (offset + length < offset) {
195 return 0;
196 }
197 if (length > realLength - offset) {
198 length = realLength - offset;
199 }
200 if (data) {
201 // skip the stream to the part of the table we want to copy from
202 stream->rewind();
203 size_t bytesToSkip = realOffset + offset;
204 if (!skip(stream, bytesToSkip)) {
205 return 0;
206 }
207 if (!read(stream, data, length)) {
208 return 0;
209 }
210 }
211 return length;
212 }
213 }
214 return 0;
215 }
216