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 #ifndef MEDIA_MP4_BOX_READER_H_ 6 #define MEDIA_MP4_BOX_READER_H_ 7 8 #include <map> 9 #include <vector> 10 11 #include "base/compiler_specific.h" 12 #include "base/logging.h" 13 #include "media/base/media_export.h" 14 #include "media/base/media_log.h" 15 #include "media/mp4/fourccs.h" 16 #include "media/mp4/rcheck.h" 17 18 namespace media { 19 namespace mp4 { 20 21 class BoxReader; 22 23 struct MEDIA_EXPORT Box { 24 virtual ~Box(); 25 virtual bool Parse(BoxReader* reader) = 0; 26 virtual FourCC BoxType() const = 0; 27 }; 28 29 class MEDIA_EXPORT BufferReader { 30 public: 31 BufferReader(const uint8* buf, const int size) 32 : buf_(buf), size_(size), pos_(0) {} 33 34 bool HasBytes(int count) { return (pos() + count <= size()); } 35 36 // Read a value from the stream, perfoming endian correction, and advance the 37 // stream pointer. 38 bool Read1(uint8* v) WARN_UNUSED_RESULT; 39 bool Read2(uint16* v) WARN_UNUSED_RESULT; 40 bool Read2s(int16* v) WARN_UNUSED_RESULT; 41 bool Read4(uint32* v) WARN_UNUSED_RESULT; 42 bool Read4s(int32* v) WARN_UNUSED_RESULT; 43 bool Read8(uint64* v) WARN_UNUSED_RESULT; 44 bool Read8s(int64* v) WARN_UNUSED_RESULT; 45 46 bool ReadFourCC(FourCC* v) WARN_UNUSED_RESULT; 47 48 bool ReadVec(std::vector<uint8>* t, int count) WARN_UNUSED_RESULT; 49 50 // These variants read a 4-byte integer of the corresponding signedness and 51 // store it in the 8-byte return type. 52 bool Read4Into8(uint64* v) WARN_UNUSED_RESULT; 53 bool Read4sInto8s(int64* v) WARN_UNUSED_RESULT; 54 55 // Advance the stream by this many bytes. 56 bool SkipBytes(int nbytes) WARN_UNUSED_RESULT; 57 58 const uint8* data() const { return buf_; } 59 int size() const { return size_; } 60 int pos() const { return pos_; } 61 62 protected: 63 const uint8* buf_; 64 int size_; 65 int pos_; 66 67 template<typename T> bool Read(T* t) WARN_UNUSED_RESULT; 68 }; 69 70 class MEDIA_EXPORT BoxReader : public BufferReader { 71 public: 72 ~BoxReader(); 73 74 // Create a BoxReader from a buffer. Note that this function may return NULL 75 // if an intact, complete box was not available in the buffer. If |*err| is 76 // set, there was a stream-level error when creating the box; otherwise, NULL 77 // values are only expected when insufficient data is available. 78 // 79 // |buf| is retained but not owned, and must outlive the BoxReader instance. 80 static BoxReader* ReadTopLevelBox(const uint8* buf, 81 const int buf_size, 82 const LogCB& log_cb, 83 bool* err); 84 85 // Read the box header from the current buffer. This function returns true if 86 // there is enough data to read the header and the header is sane; that is, it 87 // does not check to ensure the entire box is in the buffer before returning 88 // true. The semantics of |*err| are the same as above. 89 // 90 // |buf| is not retained. 91 static bool StartTopLevelBox(const uint8* buf, 92 const int buf_size, 93 const LogCB& log_cb, 94 FourCC* type, 95 int* box_size, 96 bool* err) WARN_UNUSED_RESULT; 97 98 // Returns true if |type| is recognized to be a top-level box, false 99 // otherwise. This returns true for some boxes which we do not parse. 100 // Helpful in debugging misaligned appends. 101 static bool IsValidTopLevelBox(const FourCC& type, 102 const LogCB& log_cb); 103 104 // Scan through all boxes within the current box, starting at the current 105 // buffer position. Must be called before any of the *Child functions work. 106 bool ScanChildren() WARN_UNUSED_RESULT; 107 108 // Read exactly one child box from the set of children. The type of the child 109 // will be determined by the BoxType() method of |child|. 110 bool ReadChild(Box* child) WARN_UNUSED_RESULT; 111 112 // Read one child if available. Returns false on error, true on successful 113 // read or on child absent. 114 bool MaybeReadChild(Box* child) WARN_UNUSED_RESULT; 115 116 // Read at least one child. False means error or no such child present. 117 template<typename T> bool ReadChildren( 118 std::vector<T>* children) WARN_UNUSED_RESULT; 119 120 // Read any number of children. False means error. 121 template<typename T> bool MaybeReadChildren( 122 std::vector<T>* children) WARN_UNUSED_RESULT; 123 124 // Read all children, regardless of FourCC. This is used from exactly one box, 125 // corresponding to a rather significant inconsistency in the BMFF spec. 126 // Note that this method is mutually exclusive with ScanChildren(). 127 template<typename T> bool ReadAllChildren( 128 std::vector<T>* children) WARN_UNUSED_RESULT; 129 130 // Populate the values of 'version()' and 'flags()' from a full box header. 131 // Many boxes, but not all, use these values. This call should happen after 132 // the box has been initialized, and does not re-read the main box header. 133 bool ReadFullBoxHeader() WARN_UNUSED_RESULT; 134 135 FourCC type() const { return type_; } 136 uint8 version() const { return version_; } 137 uint32 flags() const { return flags_; } 138 139 private: 140 BoxReader(const uint8* buf, const int size, const LogCB& log_cb); 141 142 // Must be called immediately after init. If the return is false, this 143 // indicates that the box header and its contents were not available in the 144 // stream or were nonsensical, and that the box must not be used further. In 145 // this case, if |*err| is false, the problem was simply a lack of data, and 146 // should only be an error condition if some higher-level component knows that 147 // no more data is coming (i.e. EOS or end of containing box). If |*err| is 148 // true, the error is unrecoverable and the stream should be aborted. 149 bool ReadHeader(bool* err); 150 151 LogCB log_cb_; 152 FourCC type_; 153 uint8 version_; 154 uint32 flags_; 155 156 typedef std::multimap<FourCC, BoxReader> ChildMap; 157 158 // The set of child box FourCCs and their corresponding buffer readers. Only 159 // valid if scanned_ is true. 160 ChildMap children_; 161 bool scanned_; 162 }; 163 164 // Template definitions 165 template<typename T> bool BoxReader::ReadChildren(std::vector<T>* children) { 166 RCHECK(MaybeReadChildren(children) && !children->empty()); 167 return true; 168 } 169 170 template<typename T> 171 bool BoxReader::MaybeReadChildren(std::vector<T>* children) { 172 DCHECK(scanned_); 173 DCHECK(children->empty()); 174 175 children->resize(1); 176 FourCC child_type = (*children)[0].BoxType(); 177 178 ChildMap::iterator start_itr = children_.lower_bound(child_type); 179 ChildMap::iterator end_itr = children_.upper_bound(child_type); 180 children->resize(std::distance(start_itr, end_itr)); 181 typename std::vector<T>::iterator child_itr = children->begin(); 182 for (ChildMap::iterator itr = start_itr; itr != end_itr; ++itr) { 183 RCHECK(child_itr->Parse(&itr->second)); 184 ++child_itr; 185 } 186 children_.erase(start_itr, end_itr); 187 188 DVLOG(2) << "Found " << children->size() << " " 189 << FourCCToString(child_type) << " boxes."; 190 return true; 191 } 192 193 template<typename T> 194 bool BoxReader::ReadAllChildren(std::vector<T>* children) { 195 DCHECK(!scanned_); 196 scanned_ = true; 197 198 bool err = false; 199 while (pos() < size()) { 200 BoxReader child_reader(&buf_[pos_], size_ - pos_, log_cb_); 201 if (!child_reader.ReadHeader(&err)) break; 202 T child; 203 RCHECK(child.Parse(&child_reader)); 204 children->push_back(child); 205 pos_ += child_reader.size(); 206 } 207 208 return !err; 209 } 210 211 } // namespace mp4 212 } // namespace media 213 214 #endif // MEDIA_MP4_BOX_READER_H_ 215
