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 "SkEndian.h" 9 #include "SkFontStream.h" 10 #include "SkStream.h" 11 12 struct SkSFNTHeader { 13 uint32_t fVersion; 14 uint16_t fNumTables; 15 uint16_t fSearchRange; 16 uint16_t fEntrySelector; 17 uint16_t fRangeShift; 18 }; 19 20 struct SkTTCFHeader { 21 uint32_t fTag; 22 uint32_t fVersion; 23 uint32_t fNumOffsets; 24 uint32_t fOffset0; // the first of N (fNumOffsets) 25 }; 26 27 union SkSharedTTHeader { 28 SkSFNTHeader fSingle; 29 SkTTCFHeader fCollection; 30 }; 31 32 struct SkSFNTDirEntry { 33 uint32_t fTag; 34 uint32_t fChecksum; 35 uint32_t fOffset; 36 uint32_t fLength; 37 }; 38 39 static bool read(SkStream* stream, void* buffer, size_t amount) { 40 return stream->read(buffer, amount) == amount; 41 } 42 43 static bool skip(SkStream* stream, size_t amount) { 44 return stream->skip(amount) == amount; 45 } 46 47 /** Return the number of tables, or if this is a TTC (collection), return the 48 number of tables in the first element of the collection. In either case, 49 if offsetToDir is not-null, set it to the offset to the beginning of the 50 table headers (SkSFNTDirEntry), relative to the start of the stream. 51 52 On an error, return 0 for number of tables, and ignore offsetToDir 53 */ 54 static int count_tables(SkStream* stream, int ttcIndex, size_t* offsetToDir) { 55 SkASSERT(ttcIndex >= 0); 56 57 SkAutoSMalloc<1024> storage(sizeof(SkSharedTTHeader)); 58 SkSharedTTHeader* header = (SkSharedTTHeader*)storage.get(); 59 60 if (!read(stream, header, sizeof(SkSharedTTHeader))) { 61 return 0; 62 } 63 64 // by default, SkSFNTHeader is at the start of the stream 65 size_t offset = 0; 66 67 // if we're really a collection, the first 4-bytes will be 'ttcf' 68 uint32_t tag = SkEndian_SwapBE32(header->fCollection.fTag); 69 if (SkSetFourByteTag('t', 't', 'c', 'f') == tag) { 70 unsigned count = SkEndian_SwapBE32(header->fCollection.fNumOffsets); 71 if ((unsigned)ttcIndex >= count) { 72 return 0; 73 } 74 75 if (ttcIndex > 0) { // need to read more of the shared header 76 stream->rewind(); 77 size_t amount = sizeof(SkSharedTTHeader) + ttcIndex * sizeof(uint32_t); 78 header = (SkSharedTTHeader*)storage.reset(amount); 79 if (!read(stream, header, amount)) { 80 return 0; 81 } 82 } 83 // this is the offset to the local SkSFNTHeader 84 offset = SkEndian_SwapBE32((&header->fCollection.fOffset0)[ttcIndex]); 85 stream->rewind(); 86 if (!skip(stream, offset)) { 87 return 0; 88 } 89 if (!read(stream, header, sizeof(SkSFNTHeader))) { 90 return 0; 91 } 92 } 93 94 if (offsetToDir) { 95 // add the size of the header, so we will point to the DirEntries 96 *offsetToDir = offset + sizeof(SkSFNTHeader); 97 } 98 return SkEndian_SwapBE16(header->fSingle.fNumTables); 99 } 100 101 /////////////////////////////////////////////////////////////////////////////// 102 103 struct SfntHeader { 104 SfntHeader() : fCount(0), fDir(NULL) {} 105 ~SfntHeader() { sk_free(fDir); } 106 107 /** If it returns true, then fCount and fDir are properly initialized. 108 Note: fDir will point to the raw array of SkSFNTDirEntry values, 109 meaning they will still be in the file's native endianness (BE). 110 111 fDir will be automatically freed when this object is destroyed 112 */ 113 bool init(SkStream* stream, int ttcIndex) { 114 stream->rewind(); 115 116 size_t offsetToDir; 117 fCount = count_tables(stream, ttcIndex, &offsetToDir); 118 if (0 == fCount) { 119 return false; 120 } 121 122 stream->rewind(); 123 if (!skip(stream, offsetToDir)) { 124 return false; 125 } 126 127 size_t size = fCount * sizeof(SkSFNTDirEntry); 128 fDir = reinterpret_cast<SkSFNTDirEntry*>(sk_malloc_throw(size)); 129 return read(stream, fDir, size); 130 } 131 132 int fCount; 133 SkSFNTDirEntry* fDir; 134 }; 135 136 /////////////////////////////////////////////////////////////////////////////// 137 138 int SkFontStream::CountTTCEntries(SkStream* stream) { 139 stream->rewind(); 140 141 SkSharedTTHeader shared; 142 if (!read(stream, &shared, sizeof(shared))) { 143 return 0; 144 } 145 146 // if we're really a collection, the first 4-bytes will be 'ttcf' 147 uint32_t tag = SkEndian_SwapBE32(shared.fCollection.fTag); 148 if (SkSetFourByteTag('t', 't', 'c', 'f') == tag) { 149 return SkEndian_SwapBE32(shared.fCollection.fNumOffsets); 150 } else { 151 return 1; // normal 'sfnt' has 1 dir entry 152 } 153 } 154 155 int SkFontStream::GetTableTags(SkStream* stream, int ttcIndex, 156 SkFontTableTag tags[]) { 157 SfntHeader header; 158 if (!header.init(stream, ttcIndex)) { 159 return 0; 160 } 161 162 if (tags) { 163 for (int i = 0; i < header.fCount; i++) { 164 tags[i] = SkEndian_SwapBE32(header.fDir[i].fTag); 165 } 166 } 167 return header.fCount; 168 } 169 170 size_t SkFontStream::GetTableData(SkStream* stream, int ttcIndex, 171 SkFontTableTag tag, 172 size_t offset, size_t length, void* data) { 173 SfntHeader header; 174 if (!header.init(stream, ttcIndex)) { 175 return 0; 176 } 177 178 for (int i = 0; i < header.fCount; i++) { 179 if (SkEndian_SwapBE32(header.fDir[i].fTag) == tag) { 180 size_t realOffset = SkEndian_SwapBE32(header.fDir[i].fOffset); 181 size_t realLength = SkEndian_SwapBE32(header.fDir[i].fLength); 182 // now sanity check the caller's offset/length 183 if (offset >= realLength) { 184 return 0; 185 } 186 // if the caller is trusting the length from the file, then a 187 // hostile file might choose a value which would overflow offset + 188 // length. 189 if (offset + length < offset) { 190 return 0; 191 } 192 if (length > realLength - offset) { 193 length = realLength - offset; 194 } 195 if (data) { 196 // skip the stream to the part of the table we want to copy from 197 stream->rewind(); 198 size_t bytesToSkip = realOffset + offset; 199 if (!skip(stream, bytesToSkip)) { 200 return 0; 201 } 202 if (!read(stream, data, length)) { 203 return 0; 204 } 205 } 206 return length; 207 } 208 } 209 return 0; 210 } 211
