Implement ISO BMFF support in Media Source.

media/mp4/box_reader.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_MP4_BOX_READER_H_
+#define MEDIA_MP4_BOX_READER_H_
+
+#include <map>
+#include <vector>
+
+#include "base/compiler_specific.h"
+#include "base/logging.h"
+#include "media/mp4/fourccs.h"
+#include "media/mp4/rcheck.h"
+
+namespace media {
+namespace mp4 {
+
+class BoxReader;
+
+struct Box {
+  virtual ~Box();
+  virtual bool Parse(BoxReader* reader) = 0;
+  virtual FourCC BoxType() const = 0;
+};
+
+class BufferReader {
+ public:
+  BufferReader(const uint8* buf, const int size)
+    : buf_(buf), size_(size), pos_(0) {}
+
+  bool HasBytes(int count) { return (pos() + count <= size()); }
+
+  // Read a value from the stream, perfoming endian correction, and advance the
+  // stream pointer.
+  bool Read1(uint8* v)  WARN_UNUSED_RESULT;
+  bool Read2(uint16* v) WARN_UNUSED_RESULT;
+  bool Read2s(int16* v) WARN_UNUSED_RESULT;
+  bool Read4(uint32* v) WARN_UNUSED_RESULT;
+  bool Read4s(int32* v) WARN_UNUSED_RESULT;
+  bool Read8(uint64* v) WARN_UNUSED_RESULT;
+  bool Read8s(int64* v) WARN_UNUSED_RESULT;
+
+  bool ReadFourCC(FourCC* v) WARN_UNUSED_RESULT;
+
+  bool ReadVec(std::vector<uint8>* t, int count) WARN_UNUSED_RESULT;
+
+  // These variants read a 4-byte integer of the corresponding signedness and
+  // store it in the 8-byte return type.
+  bool Read4Into8(uint64* v) WARN_UNUSED_RESULT;
+  bool Read4sInto8s(int64* v) WARN_UNUSED_RESULT;
+
+  // Advance the stream by this many bytes.
+  bool SkipBytes(int nbytes) WARN_UNUSED_RESULT;
+
+  int size() { return size_; }
+  int pos() { return pos_; }
+
+ protected:
+  const uint8* buf_;
+  int size_;
+  int pos_;
+
+  template<typename T> bool Read(T* t) WARN_UNUSED_RESULT;
+};
+
+class BoxReader : public BufferReader {
+ public:
+  ~BoxReader();
+
+  // Create a BoxReader from a buffer. Note that this function may return NULL
+  // if an intact, complete box was not available in the buffer. If |*err| is
+  // set, there was a stream-level error when creating the box; otherwise, NULL
+  // values are only expected when insufficient data is available.
+  //
+  // |buf| is retained but not owned, and must outlive the BoxReader instance.
+  static BoxReader* ReadTopLevelBox(const uint8* buf,
+                                    const int buf_size,
+                                    bool* err);
+
+  // Read the box header from the current buffer. This function returns true if
+  // there is enough data to read the header and the header is sane; that is, it
+  // does not check to ensure the entire box is in the buffer before returning
+  // true. The semantics of |*err| are the same as above.
+  //
+  // |buf| is not retained.
+  static bool StartTopLevelBox(const uint8* buf,
+                               const int buf_size,
+                               FourCC* type,
+                               int* box_size,
+                               bool* err) WARN_UNUSED_RESULT;
+
+  // Scan through all boxes within the current box, starting at the current
+  // buffer position. Must be called before any of the *Child functions work.
+  bool ScanChildren() WARN_UNUSED_RESULT;
+
+  // Read exactly one child box from the set of children. The type of the child
+  // will be determined by the BoxType() method of |child|.
+  bool ReadChild(Box* child) WARN_UNUSED_RESULT;
+
+  // Read one child if available. Returns false on error, true on successful
+  // read or on child absent.
+  bool MaybeReadChild(Box* child) WARN_UNUSED_RESULT;
+
+  // Read at least one child. False means error or no such child present.
+  template<typename T> bool ReadChildren(
+      std::vector<T>* children) WARN_UNUSED_RESULT;
+
+  // Read any number of children. False means error.
+  template<typename T> bool MaybeReadChildren(
+      std::vector<T>* children) WARN_UNUSED_RESULT;
+
+  // Read all children, regardless of FourCC. This is used from exactly one box,
+  // corresponding to a rather significant inconsistency in the BMFF spec.
+  template<typename T> bool ReadAllChildren(
+      std::vector<T>* children) WARN_UNUSED_RESULT;
+
+  // Populate the values of 'version()' and 'flags()' from a full box header.
+  // Many boxes, but not all, use these values. This call should happen after
+  // the box has been initialized, and does not re-read the main box header.
+  bool ReadFullBoxHeader() WARN_UNUSED_RESULT;
+
+  FourCC type() const   { return type_; }
+  uint8 version() const { return version_; }
+  uint32 flags() const  { return flags_; }
+
+ private:
+  BoxReader(const uint8* buf, const int size);
+
+  // Must be called immediately after init. If the return is false, this
+  // indicates that the box header and its contents were not available in the
+  // stream or were nonsensical, and that the box must not be used further. In
+  // this case, if |*err| is false, the problem was simply a lack of data, and
+  // should only be an error condition if some higher-level component knows that
+  // no more data is coming (i.e. EOS or end of containing box). If |*err| is
+  // true, the error is unrecoverable and the stream should be aborted.
+  bool ReadHeader(bool* err);
+
+  FourCC type_;
+  uint8 version_;
+  uint32 flags_;
+
+  typedef std::multimap<FourCC, BoxReader> ChildMap;
+
+  // The set of child box FourCCs and their corresponding buffer readers. Only
+  // valid if scanned_ is true.
+  ChildMap children_;
+  bool scanned_;
+};
+
+// Template definitions
+template<typename T> bool BoxReader::ReadChildren(std::vector<T>* children) {
+  RCHECK(MaybeReadChildren(children) && !children->empty());
+  return true;
+}
+
+template<typename T>
+bool BoxReader::MaybeReadChildren(std::vector<T>* children) {
+  DCHECK(scanned_);
+  DCHECK(children->empty());
+
+  children->resize(1);
+  FourCC child_type = (*children)[0].BoxType();
+
+  ChildMap::iterator start_itr = children_.lower_bound(child_type);
+  ChildMap::iterator end_itr = children_.upper_bound(child_type);
+  children->resize(std::distance(start_itr, end_itr));
+  typename std::vector<T>::iterator child_itr = children->begin();
+  for (ChildMap::iterator itr = start_itr; itr != end_itr; ++itr) {
+    RCHECK(child_itr->Parse(&itr->second));
+    ++child_itr;
+  }
+  children_.erase(start_itr, end_itr);
+
+  DVLOG(2) << "Found " << children->size() << " "
+           << FourCCToString(child_type) << " boxes.";
+  return true;
+}
+
+template<typename T>
+bool BoxReader::ReadAllChildren(std::vector<T>* children) {
+  DCHECK(scanned_);
+  DCHECK(children->empty());
+  RCHECK(!children_.empty());
+
+  children->resize(children_.size());
+  typename std::vector<T>::iterator child_itr = children->begin();
+  for (ChildMap::iterator itr = children_.begin();
+       itr != children_.end(); ++itr) {
+    RCHECK(child_itr->Parse(&itr->second));
+    ++child_itr;
+  }
+  children_.clear();
+  return true;
+}
+
+}  // namespace mp4
+}  // namespace media
+
+#endif  // MEDIA_MP4_BOX_READER_H_