C++ TimeRanges::Start方法代码示例

/**
 * Returns true if aValue is inside a range of aRanges, and put the range
 * index in aIntervalIndex if it is not null.
 * If aValue is not inside a range, false is returned, and aIntervalIndex, if
 * not null, is set to the index of the range which ends immediately before aValue
 * (and can be -1 if aValue is before aRanges.Start(0)).
 */
static bool
IsInRanges(TimeRanges& aRanges, double aValue, int32_t& aIntervalIndex)
{
  uint32_t length;
  aRanges.GetLength(&length);
  for (uint32_t i = 0; i < length; i++) {
    double start, end;
    aRanges.Start(i, &start);
    if (start > aValue) {
      aIntervalIndex = i - 1;
      return false;
    }
    aRanges.End(i, &end);
    if (aValue <= end) {
      aIntervalIndex = i;
      return true;
    }
  }
  aIntervalIndex = length - 1;
  return false;
}

nsresult MediaDecoder::Seek(double aTime)
{
  MOZ_ASSERT(NS_IsMainThread());
  ReentrantMonitorAutoEnter mon(GetReentrantMonitor());

  NS_ABORT_IF_FALSE(aTime >= 0.0, "Cannot seek to a negative value.");

  TimeRanges seekable;
  nsresult res;
  uint32_t length = 0;
  res = GetSeekable(&seekable);
  NS_ENSURE_SUCCESS(res, NS_OK);

  seekable.GetLength(&length);
  if (!length) {
    return NS_OK;
  }

  // If the position we want to seek to is not in a seekable range, we seek
  // to the closest position in the seekable ranges instead. If two positions
  // are equally close, we seek to the closest position from the currentTime.
  // See seeking spec, point 7 :
  // http://www.whatwg.org/specs/web-apps/current-work/multipage/the-video-element.html#seeking
  int32_t range = 0;
  if (!IsInRanges(seekable, aTime, range)) {
    if (range != -1) {
      // |range + 1| can't be negative, because the only possible negative value
      // for |range| is -1.
      if (uint32_t(range + 1) < length) {
        double leftBound, rightBound;
        res = seekable.End(range, &leftBound);
        NS_ENSURE_SUCCESS(res, NS_OK);
        res = seekable.Start(range + 1, &rightBound);
        NS_ENSURE_SUCCESS(res, NS_OK);
        double distanceLeft = Abs(leftBound - aTime);
        double distanceRight = Abs(rightBound - aTime);
        if (distanceLeft == distanceRight) {
          distanceLeft = Abs(leftBound - mCurrentTime);
          distanceRight = Abs(rightBound - mCurrentTime);
        } 
        aTime = (distanceLeft < distanceRight) ? leftBound : rightBound;
      } else {
        // Seek target is after the end last range in seekable data.
        // Clamp the seek target to the end of the last seekable range.
        res = seekable.End(length - 1, &aTime);
        NS_ENSURE_SUCCESS(res, NS_OK);
      }
    } else {
      // aTime is before the first range in |seekable|, the closest point we can
      // seek to is the start of the first range.
      seekable.Start(0, &aTime);
    }
  }

  mRequestedSeekTime = aTime;
  mCurrentTime = aTime;

  // If we are already in the seeking state, then setting mRequestedSeekTime
  // above will result in the new seek occurring when the current seek
  // completes.
  if (mPlayState != PLAY_STATE_SEEKING) {
    bool paused = false;
    if (mOwner) {
      paused = mOwner->GetPaused();
    }
    mNextState = paused ? PLAY_STATE_PAUSED : PLAY_STATE_PLAYING;
    PinForSeek();
    ChangeState(PLAY_STATE_SEEKING);
  }

  return ScheduleStateMachineThread();
}