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 "src/core/SkAutoMalloc.h"
10 #include "src/core/SkEndian.h"
11 #include "src/core/SkFontStream.h"
12
13 struct SkSFNTHeader {
14 uint32_t fVersion;
15 uint16_t fNumTables;
16 uint16_t fSearchRange;
17 uint16_t fEntrySelector;
18 uint16_t fRangeShift;
19 };
20
21 struct SkTTCFHeader {
22 uint32_t fTag;
23 uint32_t fVersion;
24 uint32_t fNumOffsets;
25 uint32_t fOffset0; // the first of N (fNumOffsets)
26 };
27
28 union SkSharedTTHeader {
29 SkSFNTHeader fSingle;
30 SkTTCFHeader fCollection;
31 };
32
33 struct SkSFNTDirEntry {
34 uint32_t fTag;
35 uint32_t fChecksum;
36 uint32_t fOffset;
37 uint32_t fLength;
38 };
39
read(SkStream * stream,void * buffer,size_t amount)40 static bool read(SkStream* stream, void* buffer, size_t amount) {
41 return stream->read(buffer, amount) == amount;
42 }
43
skip(SkStream * stream,size_t amount)44 static bool skip(SkStream* stream, size_t amount) {
45 return stream->skip(amount) == amount;
46 }
47
48 /** Return the number of tables, or if this is a TTC (collection), return the
49 number of tables in the first element of the collection. In either case,
50 if offsetToDir is not-null, set it to the offset to the beginning of the
51 table headers (SkSFNTDirEntry), relative to the start of the stream.
52
53 On an error, return 0 for number of tables, and ignore offsetToDir
54 */
count_tables(SkStream * stream,int ttcIndex,size_t * offsetToDir)55 static int count_tables(SkStream* stream, int ttcIndex, size_t* offsetToDir) {
56 SkASSERT(ttcIndex >= 0);
57
58 SkAutoSMalloc<1024> storage(sizeof(SkSharedTTHeader));
59 SkSharedTTHeader* header = (SkSharedTTHeader*)storage.get();
60
61 if (!read(stream, header, sizeof(SkSharedTTHeader))) {
62 return 0;
63 }
64
65 // by default, SkSFNTHeader is at the start of the stream
66 size_t offset = 0;
67
68 // if we're really a collection, the first 4-bytes will be 'ttcf'
69 uint32_t tag = SkEndian_SwapBE32(header->fCollection.fTag);
70 if (SkSetFourByteTag('t', 't', 'c', 'f') == tag) {
71 unsigned count = SkEndian_SwapBE32(header->fCollection.fNumOffsets);
72 if ((unsigned)ttcIndex >= count) {
73 return 0;
74 }
75
76 if (ttcIndex > 0) { // need to read more of the shared header
77 stream->rewind();
78 size_t amount = sizeof(SkSharedTTHeader) + ttcIndex * sizeof(uint32_t);
79 header = (SkSharedTTHeader*)storage.reset(amount);
80 if (!read(stream, header, amount)) {
81 return 0;
82 }
83 }
84 // this is the offset to the local SkSFNTHeader
85 offset = SkEndian_SwapBE32((&header->fCollection.fOffset0)[ttcIndex]);
86 stream->rewind();
87 if (!skip(stream, offset)) {
88 return 0;
89 }
90 if (!read(stream, header, sizeof(SkSFNTHeader))) {
91 return 0;
92 }
93 }
94
95 if (offsetToDir) {
96 // add the size of the header, so we will point to the DirEntries
97 *offsetToDir = offset + sizeof(SkSFNTHeader);
98 }
99 return SkEndian_SwapBE16(header->fSingle.fNumTables);
100 }
101
102 ///////////////////////////////////////////////////////////////////////////////
103
104 struct SfntHeader {
SfntHeaderSfntHeader105 SfntHeader() : fCount(0), fDir(nullptr) {}
~SfntHeaderSfntHeader106 ~SfntHeader() { sk_free(fDir); }
107
108 /** If it returns true, then fCount and fDir are properly initialized.
109 Note: fDir will point to the raw array of SkSFNTDirEntry values,
110 meaning they will still be in the file's native endianness (BE).
111
112 fDir will be automatically freed when this object is destroyed
113 */
initSfntHeader114 bool init(SkStream* stream, int ttcIndex) {
115 stream->rewind();
116
117 size_t offsetToDir;
118 fCount = count_tables(stream, ttcIndex, &offsetToDir);
119 if (0 == fCount) {
120 return false;
121 }
122
123 stream->rewind();
124 if (!skip(stream, offsetToDir)) {
125 return false;
126 }
127
128 size_t size = fCount * sizeof(SkSFNTDirEntry);
129 fDir = reinterpret_cast<SkSFNTDirEntry*>(sk_malloc_throw(size));
130 return read(stream, fDir, size);
131 }
132
133 int fCount;
134 SkSFNTDirEntry* fDir;
135 };
136
137 ///////////////////////////////////////////////////////////////////////////////
138
CountTTCEntries(SkStream * stream)139 int SkFontStream::CountTTCEntries(SkStream* stream) {
140 stream->rewind();
141
142 SkSharedTTHeader shared;
143 if (!read(stream, &shared, sizeof(shared))) {
144 return 0;
145 }
146
147 // if we're really a collection, the first 4-bytes will be 'ttcf'
148 uint32_t tag = SkEndian_SwapBE32(shared.fCollection.fTag);
149 if (SkSetFourByteTag('t', 't', 'c', 'f') == tag) {
150 return SkEndian_SwapBE32(shared.fCollection.fNumOffsets);
151 } else {
152 return 1; // normal 'sfnt' has 1 dir entry
153 }
154 }
155
GetTableTags(SkStream * stream,int ttcIndex,SkFontTableTag tags[])156 int SkFontStream::GetTableTags(SkStream* stream, int ttcIndex,
157 SkFontTableTag tags[]) {
158 SfntHeader header;
159 if (!header.init(stream, ttcIndex)) {
160 return 0;
161 }
162
163 if (tags) {
164 for (int i = 0; i < header.fCount; i++) {
165 tags[i] = SkEndian_SwapBE32(header.fDir[i].fTag);
166 }
167 }
168 return header.fCount;
169 }
170
GetTableData(SkStream * stream,int ttcIndex,SkFontTableTag tag,size_t offset,size_t length,void * data)171 size_t SkFontStream::GetTableData(SkStream* stream, int ttcIndex,
172 SkFontTableTag tag,
173 size_t offset, size_t length, void* data) {
174 SfntHeader header;
175 if (!header.init(stream, ttcIndex)) {
176 return 0;
177 }
178
179 for (int i = 0; i < header.fCount; i++) {
180 if (SkEndian_SwapBE32(header.fDir[i].fTag) == tag) {
181 size_t realOffset = SkEndian_SwapBE32(header.fDir[i].fOffset);
182 size_t realLength = SkEndian_SwapBE32(header.fDir[i].fLength);
183 if (offset >= realLength) {
184 // invalid
185 return 0;
186 }
187 // if the caller is trusting the length from the file, then a
188 // hostile file might choose a value which would overflow offset +
189 // length.
190 if (offset + length < offset) {
191 return 0;
192 }
193 if (length > realLength - offset) {
194 length = realLength - offset;
195 }
196 if (data) {
197 // skip the stream to the part of the table we want to copy from
198 stream->rewind();
199 size_t bytesToSkip = realOffset + offset;
200 if (!skip(stream, bytesToSkip)) {
201 return 0;
202 }
203 if (!read(stream, data, length)) {
204 return 0;
205 }
206 }
207 return length;
208 }
209 }
210 return 0;
211 }
212