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 "SkAutoMalloc.h" 9 #include "SkEndian.h" 10 #include "SkFontStream.h" 11 #include "SkStream.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 40 static bool read(SkStream* stream, void* buffer, size_t amount) { 41 return stream->read(buffer, amount) == amount; 42 } 43 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 */ 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 { 105 SfntHeader() : fCount(0), fDir(nullptr) {} 106 ~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 */ 114 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 /////////////////////////////////////////////////////////////////////////////// 138 139 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 } 155 156 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 } 170 171 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 // now sanity check the caller's offset/length 184 if (offset >= realLength) { 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
