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 "base/compiler_specific.h"
+#include "base/logging.h"
+#include "media/mp4/box_definitions.h"
+#include "media/mp4/fourccs.h"
+#include "media/mp4/rcheck.h"
+#include <map>

[acolwell GONE FROM CHROMIUM, 2012/06/06 17:32:39]

System headers go at the top

[strobe_, 2012/06/07 16:33:54]

Done.

+#include <vector>
+
+namespace media {
+namespace mp4 {
+
+class BufferReader {
+ public:
+  BufferReader(const uint8* buf, const uint64 size)
+    : buf_(buf), size_(size), pos_(0) {}
+
+  bool HasBytes(uint32 count) { return (pos() + count <= size()); }
+
+  // Read a value from the stream, perfoming endian correction, and advance the
+  // stream pointer.
+  bool Read(int8* v)   WARN_UNUSED_RESULT;

[acolwell GONE FROM CHROMIUM, 2012/06/06 17:32:39]

Add size to signatures like Read4 does below. It makes it easier to see at call
sites how much data is being read.

[strobe_, 2012/06/07 22:04:22]

Done.

+  bool Read(int16* v)  WARN_UNUSED_RESULT;
+  bool Read(int32* v)  WARN_UNUSED_RESULT;
+  bool Read(int64* v)  WARN_UNUSED_RESULT;
+  bool Read(uint8* v)  WARN_UNUSED_RESULT;
+  bool Read(uint16* v) WARN_UNUSED_RESULT;
+  bool Read(uint32* v) WARN_UNUSED_RESULT;
+  bool Read(uint64* v) WARN_UNUSED_RESULT;
+
+  bool Read(std::vector<uint8>* t, size_t 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 Read4(int64* v) WARN_UNUSED_RESULT;
+  bool Read4(uint64* v) WARN_UNUSED_RESULT;
+
+  // Advance the stream by this many bytes.
+  bool Skip(size_t nbytes) WARN_UNUSED_RESULT;
+
+  uint64 size() { return size_; }
+  uint64 pos() { return pos_; }
+
+ protected:
+  const uint8* buf_;
+  uint64 size_;
+  uint64 pos_;
+
+  template<typename T> bool Read_(T* t) WARN_UNUSED_RESULT;

[acolwell GONE FROM CHROMIUM, 2012/06/06 17:32:39]

Remove _.

[strobe_, 2012/06/07 22:04:22]

Done.

+};
+
+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

[acolwell GONE FROM CHROMIUM, 2012/06/06 17:32:39]

'*err' -> |*err|

You should also add information about the expected lifetime of |buf| relative to
the lifetime of the BoxReader object.

[strobe_, 2012/06/07 16:33:54]

Done.

+  // set, there was a stream-level error when creating the box; otherwise, NULL
+  // values are only expected when insufficient data is available.
+  static BoxReader* ReadTopLevelBox(const uint8* buf,
+                                    const size_t 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.

[acolwell GONE FROM CHROMIUM, 2012/06/06 17:32:39]

'*err' -> |*err|

[strobe_, 2012/06/07 16:33:54]

Done.

+  static bool StartTopLevelBox(const uint8* buf,
+                               const size_t buf_size,
+                               FourCC* type,
+                               size_t* 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 matching the given type from the list of children.
+  // The argument should be a Box with an associated Parse method and FourCC.
+  template<typename T> bool ReadChild(T* child) WARN_UNUSED_RESULT;
+
+  // Read one child if available. Returns false on error, true on successful
+  // read or on child absent.
+  template<typename T> bool MaybeReadChild(T* 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)

[acolwell GONE FROM CHROMIUM, 2012/06/06 17:32:39]

nit: I believe the line break should be after the ( and then you can put the
WARN_UNUSED_RESULT on the same line as the ).
Apply this here and below.

+                            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 uint64 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, and that the box must not be used further. If (result && !err),
+  // 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).
+  bool ReadHeader(bool* err);
+
+  FourCC type_;
+  uint8 version_;
+  uint32 flags_;
+
+  // The set of child box FourCCs and their corresponding buffer readers. Only
+  // valid if scanned_ is true.
+  std::multimap<FourCC, BoxReader> children_;
+  bool scanned_;
+};
+
+// Template definitions
+// TODO(strobe): Reassess my life choices vis-a-vis templates
+template<typename T> bool BoxReader::ReadChild(T* child) {
+  DCHECK(scanned_);
+  // TODO(strobe): decide how to handle inappropriately repeated boxes.
+  // If we want to be as permissive as possible, we can ignore all
+  // boxes that need repeating. On the other hand, we may simply wish to be
+  // strict about the files that we accept.
+  FourCC child_type = GetBoxType<T>();
+
+  auto itr = children_.find(child_type);

[acolwell GONE FROM CHROMIUM, 2012/06/06 17:32:39]

You might want to verify that this construct builds on all our current
platforms. You may have to be explicit about the iterator type here.

+  RCHECK(itr != children_.end());
+  DVLOG(2) << "Found a " << FourCCToString(child_type) << " box.";
+  RCHECK(Parse(&itr->second, child));

[acolwell GONE FROM CHROMIUM, 2012/06/06 17:32:39]

Ideally I'd like to see this become
RCHECK(child->Parse(&itr->second));

[strobe_, 2012/06/07 22:04:22]

Done.

+  children_.erase(itr);
+  return true;
+}
+
+template<typename T> bool BoxReader::MaybeReadChild(T* child) {
+  FourCC child_type = GetBoxType<T>();
+  if (!children_.count(child_type)) return true;
+  return ReadChild(child);
+}
+
+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());
+  FourCC child_type = GetBoxType<T>();
+  auto start_itr = children_.lower_bound(child_type);
+  auto end_itr = children_.upper_bound(child_type);
+  children->resize(std::distance(start_itr, end_itr));
+  auto child_itr = children->begin();
+  for (auto itr = start_itr; itr != end_itr; ++itr) {
+    RCHECK(Parse(&itr->second, &(*child_itr)));
+    ++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());
+  auto child_itr = children->begin();
+  for (auto itr = children_.begin(); itr != children_.end(); ++itr) {
+    RCHECK(Parse(&itr->second, &(*child_itr)));
+    ++child_itr;
+  }
+  children_.clear();
+  return true;
+}
+
+}  // namespace mp4
+}  // namespace media
+
+#endif  // MEDIA_MP4_BOX_READER_H_