shaka-packager/media/mp4/box_reader.cc

// 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.

#include "media/mp4/box_reader.h"

#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "media/mp4/box.h"

namespace media {
namespace mp4 {

BoxReader::BoxReader(const uint8* buf, size_t size)
    : BufferReader(buf, size), type_(FOURCC_NULL), scanned_(false) {
  DCHECK(buf);
  DCHECK_LT(0, size);
}

BoxReader::~BoxReader() {
  if (scanned_ && !children_.empty()) {
    for (ChildMap::iterator itr = children_.begin(); itr != children_.end();
         ++itr) {
      DVLOG(1) << "Skipping unknown box: " << FourCCToString(itr->first);
      delete itr->second;
    }
  }
}

// static
BoxReader* BoxReader::ReadTopLevelBox(const uint8* buf,
                                      const int buf_size,
                                      bool* err) {
  scoped_ptr<BoxReader> reader(new BoxReader(buf, buf_size));
  if (!reader->ReadHeader(err))
    return NULL;

  // We don't require the complete box to be available for MDAT box.
  if (reader->type() == FOURCC_MDAT)
    return reader.release();

  if (!IsValidTopLevelBox(reader->type())) {
    *err = true;
    return NULL;
  }

  if (reader->size() <= buf_size)
    return reader.release();

  return NULL;
}

// static
bool BoxReader::StartTopLevelBox(const uint8* buf,
                                 const int buf_size,
                                 FourCC* type,
                                 int* box_size,
                                 bool* err) {
  BoxReader reader(buf, buf_size);
  if (!reader.ReadHeader(err))
    return false;
  if (!IsValidTopLevelBox(reader.type())) {
    *err = true;
    return false;
  }
  *type = reader.type();
  *box_size = reader.size();
  return true;
}

// static
bool BoxReader::IsValidTopLevelBox(const FourCC& type) {
  switch (type) {
    case FOURCC_FTYP:
    case FOURCC_PDIN:
    case FOURCC_BLOC:
    case FOURCC_MOOV:
    case FOURCC_MOOF:
    case FOURCC_MFRA:
    case FOURCC_MDAT:
    case FOURCC_FREE:
    case FOURCC_SKIP:
    case FOURCC_META:
    case FOURCC_MECO:
    case FOURCC_STYP:
    case FOURCC_SIDX:
    case FOURCC_SSIX:
    case FOURCC_PRFT:
      return true;
    default:
      // Hex is used to show nonprintable characters and aid in debugging
      LOG(ERROR) << "Unrecognized top-level box type 0x" << std::hex << type;
      return false;
  }
}

bool BoxReader::ScanChildren() {
  DCHECK(!scanned_);
  scanned_ = true;

  while (pos() < size()) {
    scoped_ptr<BoxReader> child(
        new BoxReader(&data()[pos()], size() - pos()));
    bool err;
    if (!child->ReadHeader(&err))
      return false;

    FourCC box_type = child->type();
    size_t box_size = child->size();
    children_.insert(std::pair<FourCC, BoxReader*>(box_type, child.release()));
    RCHECK(SkipBytes(box_size));
  }

  return true;
}

bool BoxReader::ReadChild(Box* child) {
  DCHECK(scanned_);
  FourCC child_type = child->BoxType();

  ChildMap::iterator itr = children_.find(child_type);
  RCHECK(itr != children_.end());
  DVLOG(2) << "Found a " << FourCCToString(child_type) << " box.";
  RCHECK(child->Parse(itr->second));
  delete itr->second;
  children_.erase(itr);
  return true;
}

bool BoxReader::ChildExist(Box* child) {
  return children_.count(child->BoxType()) > 0;
}

bool BoxReader::TryReadChild(Box* child) {
  if (!children_.count(child->BoxType()))
    return true;
  return ReadChild(child);
}

bool BoxReader::ReadHeader(bool* err) {
  uint64 size = 0;
  *err = false;

  if (!ReadNBytesInto8(&size, sizeof(uint32)) || !ReadFourCC(&type_))
    return false;

  if (size == 0) {
    // Media Source specific: we do not support boxes that run to EOS.
    *err = true;
    return false;
  } else if (size == 1) {
    if (!Read8(&size))
      return false;
  }

  // Implementation-specific: support for boxes larger than 2^31 has been
  // removed.
  if (size < static_cast<uint64>(pos()) ||
      size > static_cast<uint64>(kint32max)) {
    *err = true;
    return false;
  }

  // Note that the pos_ head has advanced to the byte immediately after the
  // header, which is where we want it.
  set_size(size);
  return true;
}

}  // namespace mp4
}  // namespace media