1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "media/mp4/box_reader.h" 6 7 #include <string.h> 8 #include <algorithm> 9 #include <map> 10 #include <set> 11 12 #include "base/logging.h" 13 #include "base/memory/scoped_ptr.h" 14 #include "media/mp4/box_definitions.h" 15 #include "media/mp4/rcheck.h" 16 17 namespace media { 18 namespace mp4 { 19 20 Box::~Box() {} 21 22 bool BufferReader::Read1(uint8* v) { 23 RCHECK(HasBytes(1)); 24 *v = buf_[pos_++]; 25 return true; 26 } 27 28 // Internal implementation of multi-byte reads 29 template<typename T> bool BufferReader::Read(T* v) { 30 RCHECK(HasBytes(sizeof(T))); 31 32 T tmp = 0; 33 for (size_t i = 0; i < sizeof(T); i++) { 34 tmp <<= 8; 35 tmp += buf_[pos_++]; 36 } 37 *v = tmp; 38 return true; 39 } 40 41 bool BufferReader::Read2(uint16* v) { return Read(v); } 42 bool BufferReader::Read2s(int16* v) { return Read(v); } 43 bool BufferReader::Read4(uint32* v) { return Read(v); } 44 bool BufferReader::Read4s(int32* v) { return Read(v); } 45 bool BufferReader::Read8(uint64* v) { return Read(v); } 46 bool BufferReader::Read8s(int64* v) { return Read(v); } 47 48 bool BufferReader::ReadFourCC(FourCC* v) { 49 return Read4(reinterpret_cast<uint32*>(v)); 50 } 51 52 bool BufferReader::ReadVec(std::vector<uint8>* vec, int count) { 53 RCHECK(HasBytes(count)); 54 vec->clear(); 55 vec->insert(vec->end(), buf_ + pos_, buf_ + pos_ + count); 56 pos_ += count; 57 return true; 58 } 59 60 bool BufferReader::SkipBytes(int bytes) { 61 RCHECK(HasBytes(bytes)); 62 pos_ += bytes; 63 return true; 64 } 65 66 bool BufferReader::Read4Into8(uint64* v) { 67 uint32 tmp; 68 RCHECK(Read4(&tmp)); 69 *v = tmp; 70 return true; 71 } 72 73 bool BufferReader::Read4sInto8s(int64* v) { 74 // Beware of the need for sign extension. 75 int32 tmp; 76 RCHECK(Read4s(&tmp)); 77 *v = tmp; 78 return true; 79 } 80 81 82 BoxReader::BoxReader(const uint8* buf, const int size, 83 const LogCB& log_cb) 84 : BufferReader(buf, size), 85 log_cb_(log_cb), 86 type_(FOURCC_NULL), 87 version_(0), 88 flags_(0), 89 scanned_(false) { 90 } 91 92 BoxReader::~BoxReader() { 93 if (scanned_ && !children_.empty()) { 94 for (ChildMap::iterator itr = children_.begin(); 95 itr != children_.end(); ++itr) { 96 DVLOG(1) << "Skipping unknown box: " << FourCCToString(itr->first); 97 } 98 } 99 } 100 101 // static 102 BoxReader* BoxReader::ReadTopLevelBox(const uint8* buf, 103 const int buf_size, 104 const LogCB& log_cb, 105 bool* err) { 106 scoped_ptr<BoxReader> reader(new BoxReader(buf, buf_size, log_cb)); 107 if (!reader->ReadHeader(err)) 108 return NULL; 109 110 if (!IsValidTopLevelBox(reader->type(), log_cb)) { 111 *err = true; 112 return NULL; 113 } 114 115 if (reader->size() <= buf_size) 116 return reader.release(); 117 118 return NULL; 119 } 120 121 // static 122 bool BoxReader::StartTopLevelBox(const uint8* buf, 123 const int buf_size, 124 const LogCB& log_cb, 125 FourCC* type, 126 int* box_size, 127 bool* err) { 128 BoxReader reader(buf, buf_size, log_cb); 129 if (!reader.ReadHeader(err)) return false; 130 if (!IsValidTopLevelBox(reader.type(), log_cb)) { 131 *err = true; 132 return false; 133 } 134 *type = reader.type(); 135 *box_size = reader.size(); 136 return true; 137 } 138 139 // static 140 bool BoxReader::IsValidTopLevelBox(const FourCC& type, 141 const LogCB& log_cb) { 142 switch (type) { 143 case FOURCC_FTYP: 144 case FOURCC_PDIN: 145 case FOURCC_BLOC: 146 case FOURCC_MOOV: 147 case FOURCC_MOOF: 148 case FOURCC_MFRA: 149 case FOURCC_MDAT: 150 case FOURCC_FREE: 151 case FOURCC_SKIP: 152 case FOURCC_META: 153 case FOURCC_MECO: 154 case FOURCC_STYP: 155 case FOURCC_SIDX: 156 case FOURCC_SSIX: 157 case FOURCC_PRFT: 158 return true; 159 default: 160 // Hex is used to show nonprintable characters and aid in debugging 161 MEDIA_LOG(log_cb) << "Unrecognized top-level box type 0x" 162 << std::hex << type; 163 return false; 164 } 165 } 166 167 bool BoxReader::ScanChildren() { 168 DCHECK(!scanned_); 169 scanned_ = true; 170 171 bool err = false; 172 while (pos() < size()) { 173 BoxReader child(&buf_[pos_], size_ - pos_, log_cb_); 174 if (!child.ReadHeader(&err)) break; 175 176 children_.insert(std::pair<FourCC, BoxReader>(child.type(), child)); 177 pos_ += child.size(); 178 } 179 180 DCHECK(!err); 181 return !err && pos() == size(); 182 } 183 184 bool BoxReader::ReadChild(Box* child) { 185 DCHECK(scanned_); 186 FourCC child_type = child->BoxType(); 187 188 ChildMap::iterator itr = children_.find(child_type); 189 RCHECK(itr != children_.end()); 190 DVLOG(2) << "Found a " << FourCCToString(child_type) << " box."; 191 RCHECK(child->Parse(&itr->second)); 192 children_.erase(itr); 193 return true; 194 } 195 196 bool BoxReader::MaybeReadChild(Box* child) { 197 if (!children_.count(child->BoxType())) return true; 198 return ReadChild(child); 199 } 200 201 bool BoxReader::ReadFullBoxHeader() { 202 uint32 vflags; 203 RCHECK(Read4(&vflags)); 204 version_ = vflags >> 24; 205 flags_ = vflags & 0xffffff; 206 return true; 207 } 208 209 bool BoxReader::ReadHeader(bool* err) { 210 uint64 size = 0; 211 *err = false; 212 213 if (!HasBytes(8)) return false; 214 CHECK(Read4Into8(&size) && ReadFourCC(&type_)); 215 216 if (size == 0) { 217 // Media Source specific: we do not support boxes that run to EOS. 218 *err = true; 219 return false; 220 } else if (size == 1) { 221 if (!HasBytes(8)) return false; 222 CHECK(Read8(&size)); 223 } 224 225 // Implementation-specific: support for boxes larger than 2^31 has been 226 // removed. 227 if (size < static_cast<uint64>(pos_) || 228 size > static_cast<uint64>(kint32max)) { 229 *err = true; 230 return false; 231 } 232 233 // Note that the pos_ head has advanced to the byte immediately after the 234 // header, which is where we want it. 235 size_ = size; 236 return true; 237 } 238 239 } // namespace mp4 240 } // namespace media 241
