1 // Copyright 2014 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_FORMATS_MP4_BOX_READER_H_
6 #define MEDIA_FORMATS_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/formats/mp4/fourccs.h"
16 #include "media/formats/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:
BufferReader(const uint8 * buf,const int size)31 BufferReader(const uint8* buf, const int size)
32 : buf_(buf), size_(size), pos_(0) {
33 CHECK(buf);
34 CHECK_GE(size, 0);
35 }
36
HasBytes(int count)37 bool HasBytes(int count) { return (pos() + count <= size()); }
38
39 // Read a value from the stream, perfoming endian correction, and advance the
40 // stream pointer.
41 bool Read1(uint8* v) WARN_UNUSED_RESULT;
42 bool Read2(uint16* v) WARN_UNUSED_RESULT;
43 bool Read2s(int16* v) WARN_UNUSED_RESULT;
44 bool Read4(uint32* v) WARN_UNUSED_RESULT;
45 bool Read4s(int32* v) WARN_UNUSED_RESULT;
46 bool Read8(uint64* v) WARN_UNUSED_RESULT;
47 bool Read8s(int64* v) WARN_UNUSED_RESULT;
48
49 bool ReadFourCC(FourCC* v) WARN_UNUSED_RESULT;
50
51 bool ReadVec(std::vector<uint8>* t, int count) WARN_UNUSED_RESULT;
52
53 // These variants read a 4-byte integer of the corresponding signedness and
54 // store it in the 8-byte return type.
55 bool Read4Into8(uint64* v) WARN_UNUSED_RESULT;
56 bool Read4sInto8s(int64* v) WARN_UNUSED_RESULT;
57
58 // Advance the stream by this many bytes.
59 bool SkipBytes(int nbytes) WARN_UNUSED_RESULT;
60
data()61 const uint8* data() const { return buf_; }
size()62 int size() const { return size_; }
pos()63 int pos() const { return pos_; }
64
65 protected:
66 const uint8* buf_;
67 int size_;
68 int pos_;
69
70 template<typename T> bool Read(T* t) WARN_UNUSED_RESULT;
71 };
72
73 class MEDIA_EXPORT BoxReader : public BufferReader {
74 public:
75 ~BoxReader();
76
77 // Create a BoxReader from a buffer. Note that this function may return NULL
78 // if an intact, complete box was not available in the buffer. If |*err| is
79 // set, there was a stream-level error when creating the box; otherwise, NULL
80 // values are only expected when insufficient data is available.
81 //
82 // |buf| is retained but not owned, and must outlive the BoxReader instance.
83 static BoxReader* ReadTopLevelBox(const uint8* buf,
84 const int buf_size,
85 const LogCB& log_cb,
86 bool* err);
87
88 // Read the box header from the current buffer. This function returns true if
89 // there is enough data to read the header and the header is sane; that is, it
90 // does not check to ensure the entire box is in the buffer before returning
91 // true. The semantics of |*err| are the same as above.
92 //
93 // |buf| is not retained.
94 static bool StartTopLevelBox(const uint8* buf,
95 const int buf_size,
96 const LogCB& log_cb,
97 FourCC* type,
98 int* box_size,
99 bool* err) WARN_UNUSED_RESULT;
100
101 // Returns true if |type| is recognized to be a top-level box, false
102 // otherwise. This returns true for some boxes which we do not parse.
103 // Helpful in debugging misaligned appends.
104 static bool IsValidTopLevelBox(const FourCC& type,
105 const LogCB& log_cb);
106
107 // Scan through all boxes within the current box, starting at the current
108 // buffer position. Must be called before any of the *Child functions work.
109 bool ScanChildren() WARN_UNUSED_RESULT;
110
111 // Return true if child with type |child.BoxType()| exists.
112 bool HasChild(Box* child) WARN_UNUSED_RESULT;
113
114 // Read exactly one child box from the set of children. The type of the child
115 // will be determined by the BoxType() method of |child|.
116 bool ReadChild(Box* child) WARN_UNUSED_RESULT;
117
118 // Read one child if available. Returns false on error, true on successful
119 // read or on child absent.
120 bool MaybeReadChild(Box* child) WARN_UNUSED_RESULT;
121
122 // Read at least one child. False means error or no such child present.
123 template<typename T> bool ReadChildren(
124 std::vector<T>* children) WARN_UNUSED_RESULT;
125
126 // Read any number of children. False means error.
127 template<typename T> bool MaybeReadChildren(
128 std::vector<T>* children) WARN_UNUSED_RESULT;
129
130 // Read all children, regardless of FourCC. This is used from exactly one box,
131 // corresponding to a rather significant inconsistency in the BMFF spec.
132 // Note that this method is mutually exclusive with ScanChildren().
133 template<typename T> bool ReadAllChildren(
134 std::vector<T>* children) WARN_UNUSED_RESULT;
135
136 // Populate the values of 'version()' and 'flags()' from a full box header.
137 // Many boxes, but not all, use these values. This call should happen after
138 // the box has been initialized, and does not re-read the main box header.
139 bool ReadFullBoxHeader() WARN_UNUSED_RESULT;
140
type()141 FourCC type() const { return type_; }
version()142 uint8 version() const { return version_; }
flags()143 uint32 flags() const { return flags_; }
144
log_cb()145 const LogCB& log_cb() const { return log_cb_; }
146
147 private:
148 BoxReader(const uint8* buf, const int size, const LogCB& log_cb);
149
150 // Must be called immediately after init. If the return is false, this
151 // indicates that the box header and its contents were not available in the
152 // stream or were nonsensical, and that the box must not be used further. In
153 // this case, if |*err| is false, the problem was simply a lack of data, and
154 // should only be an error condition if some higher-level component knows that
155 // no more data is coming (i.e. EOS or end of containing box). If |*err| is
156 // true, the error is unrecoverable and the stream should be aborted.
157 bool ReadHeader(bool* err);
158
159 LogCB log_cb_;
160 FourCC type_;
161 uint8 version_;
162 uint32 flags_;
163
164 typedef std::multimap<FourCC, BoxReader> ChildMap;
165
166 // The set of child box FourCCs and their corresponding buffer readers. Only
167 // valid if scanned_ is true.
168 ChildMap children_;
169 bool scanned_;
170 };
171
172 // Template definitions
ReadChildren(std::vector<T> * children)173 template<typename T> bool BoxReader::ReadChildren(std::vector<T>* children) {
174 RCHECK(MaybeReadChildren(children) && !children->empty());
175 return true;
176 }
177
178 template<typename T>
MaybeReadChildren(std::vector<T> * children)179 bool BoxReader::MaybeReadChildren(std::vector<T>* children) {
180 DCHECK(scanned_);
181 DCHECK(children->empty());
182
183 children->resize(1);
184 FourCC child_type = (*children)[0].BoxType();
185
186 ChildMap::iterator start_itr = children_.lower_bound(child_type);
187 ChildMap::iterator end_itr = children_.upper_bound(child_type);
188 children->resize(std::distance(start_itr, end_itr));
189 typename std::vector<T>::iterator child_itr = children->begin();
190 for (ChildMap::iterator itr = start_itr; itr != end_itr; ++itr) {
191 RCHECK(child_itr->Parse(&itr->second));
192 ++child_itr;
193 }
194 children_.erase(start_itr, end_itr);
195
196 DVLOG(2) << "Found " << children->size() << " "
197 << FourCCToString(child_type) << " boxes.";
198 return true;
199 }
200
201 template<typename T>
ReadAllChildren(std::vector<T> * children)202 bool BoxReader::ReadAllChildren(std::vector<T>* children) {
203 DCHECK(!scanned_);
204 scanned_ = true;
205
206 bool err = false;
207 while (pos() < size()) {
208 BoxReader child_reader(&buf_[pos_], size_ - pos_, log_cb_);
209 if (!child_reader.ReadHeader(&err)) break;
210 T child;
211 RCHECK(child.Parse(&child_reader));
212 children->push_back(child);
213 pos_ += child_reader.size();
214 }
215
216 return !err;
217 }
218
219 } // namespace mp4
220 } // namespace media
221
222 #endif // MEDIA_FORMATS_MP4_BOX_READER_H_
223