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 PACKAGER_MEDIA_FORMATS_MP4_BOX_READER_H_
#define PACKAGER_MEDIA_FORMATS_MP4_BOX_READER_H_
 
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <map>
#include <memory>
#include <vector>
 
#include <absl/log/check.h>
#include <absl/log/log.h>
 
#include <packager/macros/classes.h>
#include <packager/media/base/buffer_reader.h>
#include <packager/media/base/fourccs.h>
#include <packager/media/base/rcheck.h>
 
namespace shaka {
namespace media {
namespace mp4 {
 
struct Box;
 
class BoxReader : public BufferReader {
 public:
  ~BoxReader();
 
  static BoxReader* ReadBox(const uint8_t* buf,
                            const size_t buf_size,
                            bool* err);
 
  [[nodiscard]] static bool StartBox(const uint8_t* buf,
                                     const size_t buf_size,
                                     FourCC* type,
                                     uint64_t* box_size,
                                     bool* err);
 
  [[nodiscard]] bool ScanChildren();
 
  [[nodiscard]] bool ChildExist(Box* child);
 
  [[nodiscard]] bool ReadChild(Box* child);
 
  [[nodiscard]] bool TryReadChild(Box* child);
 
  template <typename T>
  [[nodiscard]] bool ReadChildren(std::vector<T>* children);
 
  template <typename T>
  [[nodiscard]] bool TryReadChildren(std::vector<T>* children);
 
  template <typename T>
  [[nodiscard]] bool ReadAllChildren(std::vector<T>* children);
 
  bool ReadFourCC(FourCC* fourcc) {
    uint32_t val;
    if (!Read4(&val))
      return false;
    *fourcc = static_cast<FourCC>(val);
    return true;
  }
 
  FourCC type() const { return type_; }
 
 private:
  BoxReader(const uint8_t* buf, size_t 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_;
 
  typedef std::multimap<FourCC, std::unique_ptr<BoxReader>> ChildMap;
 
  // The set of child box FourCCs and their corresponding buffer readers. Only
  // valid if scanned_ is true.
  ChildMap children_;
  bool scanned_;
 
  DISALLOW_COPY_AND_ASSIGN(BoxReader);
};
 
// Template definitions.
template <typename T>
bool BoxReader::ReadChildren(std::vector<T>* children) {
  RCHECK(TryReadChildren(children) && !children->empty());
  return true;
}
 
template <typename T>
bool BoxReader::TryReadChildren(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.get()));
    ++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_);
  scanned_ = true;
 
  while (pos() < size()) {
    BoxReader child_reader(&data()[pos()], size() - pos());
    bool err;
    if (!child_reader.ReadHeader(&err))
      return false;
 
    T child;
    RCHECK(child.Parse(&child_reader));
    children->push_back(child);
    RCHECK(SkipBytes(child_reader.size()));
  }
 
  return true;
}
 
}  // namespace mp4
}  // namespace media
}  // namespace shaka
 
#endif  // PACKAGER_MEDIA_FORMATS_MP4_BOX_READER_H_