Add initial implementation of SourceBufferStream

media/filters/source_buffer_stream.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/filters/source_buffer_stream.h"
+
+#include <algorithm>
+#include <map>
+
+#include "base/logging.h"
+
+namespace media {
+
+// Helper class representing a range of buffered data. All buffers in a
+// SourceBufferRange are ordered sequentially in presentation order with no
+// gaps.
+class SourceBufferRange {
+ public:
+  typedef std::deque<scoped_refptr<StreamParserBuffer> > BufferQueue;
+
+  SourceBufferRange();
+
+  // Adds |new_buffers| into this range. |new_buffers| must belong to this
+  // range. Garbage collection may occur after Append().
+  void Append(const BufferQueue& new_buffers);
+
+  // Updates |next_buffer_index_| to point to the Buffer containing |timestamp|.
+  // Assumes |timestamp| is valid and in this range.
+  void Seek(base::TimeDelta timestamp);
+
+  // Updates |out_buffer| with the next buffer in presentation order. Seek()
+  // must be called before calls to GetNextBuffer(), and buffers are returned
+  // in order from the last call to Seek(). Returns true if |out_buffer| is
+  // filled with a valid buffer, false if there is not enough data to fulfill
+  // the request.
+  bool GetNextBuffer(scoped_refptr<StreamParserBuffer>* out_buffer);
+
+  // Returns the Timespan of buffered time in this range.
+  SourceBufferStream::Timespan GetBufferedTime() const;
+
+  // Appends the buffers from |range| into this range.
+  // The first buffer in |range| must come directly after the last buffer
+  // in this range.
+  // If |transfer_current_position| is true, |range|'s |next_buffer_position_|
+  // is transfered to this SourceBufferRange.
+  void AppendRange(const SourceBufferRange& range,
+                   bool transfer_current_position);
+  bool CanAppendRange(const SourceBufferRange& range) const;
+
+  // Returns whether a buffer with a starting timestamp of |timestamp| would
+  // belong in this range. This includes a buffer that would be appended to
+  // the end of the range.
+  // Returns 0 if |timestamp| is in this range, -1 if |timestamp| appears
+  // before this range, or 1 if |timestamp| appears after this range.
+  int BelongsToRange(base::TimeDelta timestamp) const;
+
+  // Returns true if the range has enough data to seek to the specified
+  // |timestamp|, false otherwise.
+  bool CanSeekTo(base::TimeDelta timestamp) const;
+
+  // Returns true if the end of this range contains buffers that overlaps with
+  // the beginning of |range|.
+  bool EndOverlaps(const SourceBufferRange& range) const;
+
+ private:
+  // Appends |buffers| to the end of the range and updates |keyframe_map_| as
+  // it encounters new keyframes. Assumes |buffers| belongs at the end of the
+  // range.
+  void AppendToEnd(const BufferQueue& buffers);
+
+  // Returns the start timestamp of the range, or kNoTimestamp if the range is
+  // empty.
+  base::TimeDelta BufferedStart() const;
+
+  // Returns the end timestamp of the buffered data. (Note that this is equal to
+  // the last buffer's timestamp + its duration.) Returns kNoTimestamp if the
+  // range is empty.
+  base::TimeDelta BufferedEnd() const;
+
+  // Returns the upper bound for the starting timestamp for the next buffer to
+  // be appended at the end of the range. Should only be called if |buffers_| is
+  // nonempty.
+  base::TimeDelta MaxNextTimestamp() const;
+
+  // An ordered list of buffers in this range.
+  BufferQueue buffers_;
+
+  // Maps keyframe timestamps to its index position in |buffers_|.
+  typedef std::map<base::TimeDelta, size_t> KeyframeMap;
+  KeyframeMap keyframe_map_;
+
+  // Index into |buffers_| for the next buffer to be returned by
+  // GetBufferedTime(), set to -1 before Seek().
+  int next_buffer_index_;
+
+  DISALLOW_COPY_AND_ASSIGN(SourceBufferRange);
+};
+
+}  // namespace media
+
+// Helper method that returns true if |ranges| is sorted in increasing order,
+// false otherwise.
+static bool IsRangeListSorted(
+    const std::list<media::SourceBufferRange*>& ranges) {
+  base::TimeDelta prev = media::kNoTimestamp();
+  for (std::list<media::SourceBufferRange*>::const_iterator itr =
+       ranges.begin(); itr != ranges.end(); itr++) {
+    media::SourceBufferStream::Timespan buffered = (*itr)->GetBufferedTime();
+    if (prev != media::kNoTimestamp() && prev >= buffered.first)
+      return false;
+    prev = buffered.second;
+  }
+  return true;
+}
+
+// Comparison function for two Buffers based on timestamp.
+static bool BufferComparator(scoped_refptr<media::Buffer> first,
+                             scoped_refptr<media::Buffer> second) {
+  return first->GetTimestamp() < second->GetTimestamp();
+}
+
+namespace media {
+
+SourceBufferStream::SourceBufferStream()
+    : seek_pending_(false),
+      seek_buffer_timestamp_(kNoTimestamp()),
+      selected_range_(NULL) {
+}
+
+SourceBufferStream::~SourceBufferStream() {
+  while (!ranges_.empty()) {
+    delete ranges_.front();
+    ranges_.pop_front();
+  }
+}
+
+bool SourceBufferStream::Append(
+    const SourceBufferStream::BufferQueue& buffers) {
+  DCHECK(!buffers.empty());
+  base::TimeDelta start_timestamp = buffers.front()->GetTimestamp();
+  base::TimeDelta end_timestamp = buffers.back()->GetTimestamp();
+
+  // Check to see if |buffers| will overlap the currently |selected_range_|,
+  // and if so, ignore this Append() request.
+  // TODO(vrk): Support end overlap properly. (crbug.com/125072)
+  if (selected_range_) {
+    Timespan selected_range_span = selected_range_->GetBufferedTime();
+    if (selected_range_span.second > start_timestamp &&
+        selected_range_span.first <= end_timestamp) {
+      return false;
+    }
+  }
+
+  SourceBufferRange* range = NULL;
+  RangeList::iterator itr = ranges_.end();
+  for (itr = ranges_.begin(); itr != ranges_.end(); itr++) {
+    int range_value = (*itr)->BelongsToRange(start_timestamp);
+
+    // |start_timestamp| is before the current range in this loop. Because
+    // |ranges_| is sorted, this means that we need to create a new range and it
+    // should be placed before |itr|.
+    if (range_value < 0)
+      break;
+
+    if (range_value == 0) {
+      // Found an existing range into which we can append buffers.
+      range = *itr;
+      break;
+    }
+  }
+
+  if (!range) {
+    // Ranges must begin with a keyframe.
+    if (!buffers.front()->IsKeyframe())
+      return false;
+
+    range = new SourceBufferRange();
+    itr = ranges_.insert(itr, range);
+  }
+
+  // Append buffers to the appropriate range.
+  range->Append(buffers);
+
+  // Increment |itr| to be the range after |range|.
+  itr++;
+
+  // Handle overlaps if they were created.
+  while (itr != ranges_.end() && range->EndOverlaps(**itr)) {
+    DCHECK_NE(*itr, selected_range_);
+    delete *itr;
+    itr = ranges_.erase(itr);
+  }
+
+  // Merge with neighbor if necessary.
+  if (itr != ranges_.end() && range->CanAppendRange(**itr)) {
+    bool transfer_current_position = selected_range_ == *itr;
+    range->AppendRange(**itr, transfer_current_position);
+    // Update |selected_range_| pointer if |range| has become selected after
+    // merges.
+    if (transfer_current_position)
+      selected_range_ = range;
+
+    delete *itr;
+    ranges_.erase(itr);
+  }
+
+  // Finally, try to complete pending seek if one exists.
+  if (seek_pending_)
+    Seek(seek_buffer_timestamp_);
+
+  DCHECK(IsRangeListSorted(ranges_));
+  return true;
+}
+
+void SourceBufferStream::Seek(base::TimeDelta timestamp) {
+  if (selected_range_)
+    selected_range_ = NULL;
+
+  seek_buffer_timestamp_ = timestamp;
+  seek_pending_ = true;
+
+  RangeList::iterator itr = ranges_.end();
+  for (itr = ranges_.begin(); itr != ranges_.end(); itr++) {
+    if ((*itr)->CanSeekTo(timestamp))
+      break;
+  }
+
+  if (itr == ranges_.end())
+    return;
+
+  selected_range_ = *itr;
+  selected_range_->Seek(timestamp);
+  seek_pending_ = false;
+}
+
+bool SourceBufferStream::GetNextBuffer(
+    scoped_refptr<StreamParserBuffer>* out_buffer) {
+  return selected_range_ && selected_range_->GetNextBuffer(out_buffer);
+}
+
+std::list<SourceBufferStream::Timespan>
+SourceBufferStream::GetBufferedTime() const {
+  std::list<Timespan> timespans;
+  for (RangeList::const_iterator itr = ranges_.begin();
+       itr != ranges_.end(); itr++) {
+    timespans.push_back((*itr)->GetBufferedTime());
+  }
+  return timespans;
+}
+
+SourceBufferRange::SourceBufferRange()
+    : next_buffer_index_(-1) {
+}
+
+void SourceBufferRange::Append(const BufferQueue& new_buffers) {
+  base::TimeDelta start_timestamp = new_buffers.front()->GetTimestamp();
+
+  if (!buffers_.empty() && start_timestamp < BufferedEnd()) {
+    // We are overwriting existing data, so find the starting point where
+    // things will get overwritten.
+    BufferQueue::iterator starting_point =
+        std::lower_bound(buffers_.begin(), buffers_.end(),
+                         new_buffers.front(),
+                         BufferComparator);
+
+    // Remove everything from |starting_point| onward.
+    buffers_.erase(starting_point, buffers_.end());
+  }
+
+  // Append data.
+  AppendToEnd(new_buffers);
+}
+
+void SourceBufferRange::AppendToEnd(const BufferQueue& new_buffers) {
+  for (BufferQueue::const_iterator itr = new_buffers.begin();
+       itr != new_buffers.end(); itr++) {
+    DCHECK((*itr)->GetDuration() > base::TimeDelta());
+    DCHECK((*itr)->GetTimestamp() != kNoTimestamp());
+    buffers_.push_back(*itr);
+    if ((*itr)->IsKeyframe()) {
+      keyframe_map_.insert(
+          std::make_pair((*itr)->GetTimestamp(), buffers_.size() - 1));
+    }
+  }
+}
+
+void SourceBufferRange::Seek(base::TimeDelta timestamp) {
+  DCHECK(CanSeekTo(timestamp));
+  DCHECK(!keyframe_map_.empty());
+
+  KeyframeMap::iterator result = keyframe_map_.lower_bound(timestamp);
+  // lower_bound() returns the first element >= |timestamp|, so we want the
+  // previous element if it did not return the element exactly equal to
+  // |timestamp|.
+  if (result == keyframe_map_.end() || result->first != timestamp) {
+    DCHECK(result != keyframe_map_.begin());
+    result--;
+  }
+  next_buffer_index_ = result->second;
+  DCHECK_LT(next_buffer_index_, static_cast<int>(buffers_.size()));
+}
+
+bool SourceBufferRange::GetNextBuffer(
+    scoped_refptr<StreamParserBuffer>* out_buffer) {
+  DCHECK_GE(next_buffer_index_, 0);
+  if (next_buffer_index_ >= static_cast<int>(buffers_.size()))
+    return false;
+
+  *out_buffer = buffers_.at(next_buffer_index_);
+  next_buffer_index_++;
+  return true;
+}
+
+SourceBufferStream::Timespan
+SourceBufferRange::GetBufferedTime() const {
+  return std::make_pair(BufferedStart(), BufferedEnd());
+}
+
+void SourceBufferRange::AppendRange(const SourceBufferRange& range,
+                                    bool transfer_current_position) {
+  DCHECK(CanAppendRange(range));
+  DCHECK(!buffers_.empty());
+
+  if (transfer_current_position)
+    next_buffer_index_ = range.next_buffer_index_ + buffers_.size();
+
+  AppendToEnd(range.buffers_);
+}
+
+bool SourceBufferRange::CanAppendRange(const SourceBufferRange& range) const {
+  return range.BufferedStart() >= BufferedEnd() &&
+      range.BufferedStart() <= MaxNextTimestamp();
+}
+
+int SourceBufferRange::BelongsToRange(base::TimeDelta timestamp) const {
+  if (buffers_.empty() || MaxNextTimestamp() < timestamp)
+    return 1;
+  else if (BufferedStart() > timestamp)
+    return -1;
+  else
+    return 0;
+}
+
+bool SourceBufferRange::CanSeekTo(base::TimeDelta timestamp) const {
+  return !keyframe_map_.empty() && BufferedStart() <= timestamp &&
+      BufferedEnd() > timestamp;
+}
+
+bool SourceBufferRange::EndOverlaps(const SourceBufferRange& range) const {
+  return range.BufferedStart() < BufferedEnd();
+}
+
+base::TimeDelta SourceBufferRange::BufferedStart() const {
+  if (buffers_.empty())
+    return kNoTimestamp();
+
+  return buffers_.front()->GetTimestamp();
+}
+
+base::TimeDelta SourceBufferRange::BufferedEnd() const {
+  if (buffers_.empty())
+    return kNoTimestamp();
+
+  return buffers_.back()->GetTimestamp() + buffers_.back()->GetDuration();
+}
+
+base::TimeDelta SourceBufferRange::MaxNextTimestamp() const {
+  DCHECK(!buffers_.empty());
+
+  // Because we do not know exactly when is the next timestamp, any buffer
+  // that starts within 1/3 of the duration past the end of the last buffer
+  // in the queue is considered the next buffer in this range.
+  return BufferedEnd() + buffers_.back()->GetDuration() / 3;
+}
+
+}  // namespace media