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 #include "media/formats/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/formats/mp4/box_definitions.h"
15 #include "media/formats/mp4/rcheck.h"
16
17 namespace media {
18 namespace mp4 {
19
~Box()20 Box::~Box() {}
21
Read1(uint8 * v)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
Read(T * v)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
Read2(uint16 * v)41 bool BufferReader::Read2(uint16* v) { return Read(v); }
Read2s(int16 * v)42 bool BufferReader::Read2s(int16* v) { return Read(v); }
Read4(uint32 * v)43 bool BufferReader::Read4(uint32* v) { return Read(v); }
Read4s(int32 * v)44 bool BufferReader::Read4s(int32* v) { return Read(v); }
Read8(uint64 * v)45 bool BufferReader::Read8(uint64* v) { return Read(v); }
Read8s(int64 * v)46 bool BufferReader::Read8s(int64* v) { return Read(v); }
47
ReadFourCC(FourCC * v)48 bool BufferReader::ReadFourCC(FourCC* v) {
49 return Read4(reinterpret_cast<uint32*>(v));
50 }
51
ReadVec(std::vector<uint8> * vec,int count)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
SkipBytes(int bytes)60 bool BufferReader::SkipBytes(int bytes) {
61 RCHECK(HasBytes(bytes));
62 pos_ += bytes;
63 return true;
64 }
65
Read4Into8(uint64 * v)66 bool BufferReader::Read4Into8(uint64* v) {
67 uint32 tmp;
68 RCHECK(Read4(&tmp));
69 *v = tmp;
70 return true;
71 }
72
Read4sInto8s(int64 * v)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
BoxReader(const uint8 * buf,const int size,const LogCB & log_cb)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
~BoxReader()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
ReadTopLevelBox(const uint8 * buf,const int buf_size,const LogCB & log_cb,bool * err)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
StartTopLevelBox(const uint8 * buf,const int buf_size,const LogCB & log_cb,FourCC * type,int * box_size,bool * err)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
IsValidTopLevelBox(const FourCC & type,const LogCB & log_cb)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 case FOURCC_UUID:
159 case FOURCC_EMSG:
160 return true;
161 default:
162 // Hex is used to show nonprintable characters and aid in debugging
163 MEDIA_LOG(log_cb) << "Unrecognized top-level box type "
164 << FourCCToString(type);
165 return false;
166 }
167 }
168
ScanChildren()169 bool BoxReader::ScanChildren() {
170 DCHECK(!scanned_);
171 scanned_ = true;
172
173 bool err = false;
174 while (pos() < size()) {
175 BoxReader child(&buf_[pos_], size_ - pos_, log_cb_);
176 if (!child.ReadHeader(&err)) break;
177
178 children_.insert(std::pair<FourCC, BoxReader>(child.type(), child));
179 pos_ += child.size();
180 }
181
182 DCHECK(!err);
183 return !err && pos() == size();
184 }
185
HasChild(Box * child)186 bool BoxReader::HasChild(Box* child) {
187 DCHECK(scanned_);
188 DCHECK(child);
189 return children_.count(child->BoxType()) > 0;
190 }
191
ReadChild(Box * child)192 bool BoxReader::ReadChild(Box* child) {
193 DCHECK(scanned_);
194 FourCC child_type = child->BoxType();
195
196 ChildMap::iterator itr = children_.find(child_type);
197 RCHECK(itr != children_.end());
198 DVLOG(2) << "Found a " << FourCCToString(child_type) << " box.";
199 RCHECK(child->Parse(&itr->second));
200 children_.erase(itr);
201 return true;
202 }
203
MaybeReadChild(Box * child)204 bool BoxReader::MaybeReadChild(Box* child) {
205 if (!children_.count(child->BoxType())) return true;
206 return ReadChild(child);
207 }
208
ReadFullBoxHeader()209 bool BoxReader::ReadFullBoxHeader() {
210 uint32 vflags;
211 RCHECK(Read4(&vflags));
212 version_ = vflags >> 24;
213 flags_ = vflags & 0xffffff;
214 return true;
215 }
216
ReadHeader(bool * err)217 bool BoxReader::ReadHeader(bool* err) {
218 uint64 size = 0;
219 *err = false;
220
221 if (!HasBytes(8)) return false;
222 CHECK(Read4Into8(&size) && ReadFourCC(&type_));
223
224 if (size == 0) {
225 // Media Source specific: we do not support boxes that run to EOS.
226 *err = true;
227 return false;
228 } else if (size == 1) {
229 if (!HasBytes(8)) return false;
230 CHECK(Read8(&size));
231 }
232
233 // Implementation-specific: support for boxes larger than 2^31 has been
234 // removed.
235 if (size < static_cast<uint64>(pos_) ||
236 size > static_cast<uint64>(kint32max)) {
237 *err = true;
238 return false;
239 }
240
241 // Note that the pos_ head has advanced to the byte immediately after the
242 // header, which is where we want it.
243 size_ = size;
244 return true;
245 }
246
247 } // namespace mp4
248 } // namespace media
249