C++ MediaResource::Read方法代码示例

/*
 * If we're not at end of stream, read |aNumBytes| from the media resource,
 * put it in |aData|, and return true.
 * Otherwise, put as much data as is left into |aData|, set |aNumBytes| to the
 * amount of data we have left, and return false.
 */
nsresult
AppleMP3Reader::Read(uint32_t *aNumBytes, char *aData)
{
  MediaResource *resource = mDecoder->GetResource();

  // Loop until we have all the data asked for, or we've reached EOS
  uint32_t totalBytes = 0;
  uint32_t numBytes;
  do {
    uint32_t bytesWanted = *aNumBytes - totalBytes;
    nsresult rv = resource->Read(aData + totalBytes, bytesWanted, &numBytes);
    totalBytes += numBytes;

    if (NS_FAILED(rv)) {
      *aNumBytes = 0;
      return NS_ERROR_FAILURE;
    }
  } while(totalBytes < *aNumBytes && numBytes);

  *aNumBytes = totalBytes;

  // We will have read some data in the last iteration iff we filled the buffer.
  // XXX Maybe return a better value than NS_ERROR_FAILURE?
  return numBytes ? NS_OK : NS_ERROR_FAILURE;
}

void nsGStreamerReader::ReadAndPushData(guint aLength)
{
  MediaResource* resource = mDecoder->GetResource();
  NS_ASSERTION(resource, "Decoder has no media resource");
  nsresult rv = NS_OK;

  GstBuffer *buffer = gst_buffer_new_and_alloc(aLength);
  guint8 *data = GST_BUFFER_DATA(buffer);
  uint32_t size = 0, bytesRead = 0;
  while(bytesRead < aLength) {
    rv = resource->Read(reinterpret_cast<char*>(data + bytesRead),
        aLength - bytesRead, &size);
    if (NS_FAILED(rv) || size == 0)
      break;

    bytesRead += size;
  }

  GST_BUFFER_SIZE(buffer) = bytesRead;
  mByteOffset += bytesRead;

  GstFlowReturn ret = gst_app_src_push_buffer(mSource, gst_buffer_ref(buffer));
  if (ret != GST_FLOW_OK)
    LOG(PR_LOG_ERROR, ("ReadAndPushData push ret %s", gst_flow_get_name(ret)));

  if (GST_BUFFER_SIZE (buffer) < aLength)
    /* If we read less than what we wanted, we reached the end */
    gst_app_src_end_of_stream(mSource);

  gst_buffer_unref(buffer);
}

// Functions for reading and seeking using MediaResource required for
// nestegg_io. The 'user data' passed to these functions is the
// decoder from which the media resource is obtained.
static int webm_read(void *aBuffer, size_t aLength, void *aUserData)
{
  NS_ASSERTION(aUserData, "aUserData must point to a valid nsBuiltinDecoder");
  nsBuiltinDecoder* decoder = reinterpret_cast<nsBuiltinDecoder*>(aUserData);
  MediaResource* resource = decoder->GetResource();
  NS_ASSERTION(resource, "Decoder has no media resource");

  nsresult rv = NS_OK;
  bool eof = false;

  char *p = static_cast<char *>(aBuffer);
  while (NS_SUCCEEDED(rv) && aLength > 0) {
    PRUint32 bytes = 0;
    rv = resource->Read(p, aLength, &bytes);
    if (bytes == 0) {
      eof = true;
      break;
    }
    decoder->NotifyBytesConsumed(bytes);
    aLength -= bytes;
    p += bytes;
  }

  return NS_FAILED(rv) ? -1 : eof ? 0 : 1;
}

void GStreamerReader::PlayBinSourceSetup(GstAppSrc* aSource)
{
  mSource = GST_APP_SRC(aSource);
  gst_app_src_set_callbacks(mSource, &mSrcCallbacks, (gpointer) this, nullptr);
  MediaResource* resource = mDecoder->GetResource();

  /* do a short read to trigger a network request so that GetLength() below
   * returns something meaningful and not -1
   */
  char buf[512];
  unsigned int size = 0;
  resource->Read(buf, sizeof(buf), &size);
  resource->Seek(SEEK_SET, 0);

  /* now we should have a length */
  int64_t resourceLength = resource->GetLength();
  gst_app_src_set_size(mSource, resourceLength);
  if (resource->IsDataCachedToEndOfResource(0) ||
      (resourceLength != -1 && resourceLength <= SHORT_FILE_SIZE)) {
    /* let the demuxer work in pull mode for local files (or very short files)
     * so that we get optimal seeking accuracy/performance
     */
    LOG(PR_LOG_DEBUG, ("configuring random access, len %lld", resourceLength));
    gst_app_src_set_stream_type(mSource, GST_APP_STREAM_TYPE_RANDOM_ACCESS);
  } else {
    /* make the demuxer work in push mode so that seeking is kept to a minimum
     */
    LOG(PR_LOG_DEBUG, ("configuring push mode, len %lld", resourceLength));
    gst_app_src_set_stream_type(mSource, GST_APP_STREAM_TYPE_SEEKABLE);
  }
}

static bool Read(Decoder *aDecoder, char *aBuffer, int64_t aOffset, uint32_t aCount, uint32_t* aBytes)
{
  MediaResource *resource = GetResource(aDecoder);
  if (aOffset != resource->Tell()) {
    nsresult rv = resource->Seek(nsISeekableStream::NS_SEEK_SET, aOffset);
    if (NS_FAILED(rv)) {
      return false;
    }
  }
  nsresult rv = resource->Read(aBuffer, aCount, aBytes);
  if (NS_FAILED(rv)) {
    return false;
  }
  return true;
}

void GStreamerReader::ReadAndPushData(guint aLength)
{
  MediaResource* resource = mDecoder->GetResource();
  NS_ASSERTION(resource, "Decoder has no media resource");
  nsresult rv = NS_OK;

  GstBuffer* buffer = gst_buffer_new_and_alloc(aLength);
#if GST_VERSION_MAJOR >= 1
  GstMapInfo info;
  gst_buffer_map(buffer, &info, GST_MAP_WRITE);
  guint8 *data = info.data;
#else
  guint8* data = GST_BUFFER_DATA(buffer);
#endif
  uint32_t size = 0, bytesRead = 0;
  while(bytesRead < aLength) {
    rv = resource->Read(reinterpret_cast<char*>(data + bytesRead),
        aLength - bytesRead, &size);
    if (NS_FAILED(rv) || size == 0)
      break;

    bytesRead += size;
  }

#if GST_VERSION_MAJOR >= 1
  gst_buffer_unmap(buffer, &info);
  gst_buffer_set_size(buffer, bytesRead);
#else
  GST_BUFFER_SIZE(buffer) = bytesRead;
#endif

  GstFlowReturn ret = gst_app_src_push_buffer(mSource, gst_buffer_ref(buffer));
  if (ret != GST_FLOW_OK) {
    LOG(PR_LOG_ERROR, ("ReadAndPushData push ret %s", gst_flow_get_name(ret)));
  }

  if (bytesRead < aLength) {
    /* If we read less than what we wanted, we reached the end */
    gst_app_src_end_of_stream(mSource);
  }

  gst_buffer_unref(buffer);
}

/*
 * If we're not at end of stream, read |aNumBytes| from the media resource,
 * put it in |aData|, and return true.
 * Otherwise, put as much data as is left into |aData|, set |aNumBytes| to the
 * amount of data we have left, and return false.
 *
 * This function also passes the read data on to the MP3 frame parser for
 * stream duration estimation.
 */
nsresult
AppleMP3Reader::ReadAndNotify(uint32_t *aNumBytes, char *aData)
{
    MediaResource *resource = mDecoder->GetResource();

    uint64_t offset = resource->Tell();

    // Loop until we have all the data asked for, or we've reached EOS
    uint32_t totalBytes = 0;
    uint32_t numBytes;
    do {
        uint32_t bytesWanted = *aNumBytes - totalBytes;
        nsresult rv = resource->Read(aData + totalBytes, bytesWanted, &numBytes);
        totalBytes += numBytes;

        if (NS_FAILED(rv)) {
            *aNumBytes = 0;
            return NS_ERROR_FAILURE;
        }
    } while(totalBytes < *aNumBytes && numBytes);

    // Pass the buffer to the MP3 frame parser to improve our duration estimate.
    if (mMP3FrameParser.IsMP3()) {
        mMP3FrameParser.Parse(aData, totalBytes, offset);
        uint64_t duration = mMP3FrameParser.GetDuration();
        if (duration != mDuration) {
            LOGD("Updating media duration to %lluus\n", duration);
            mDuration = duration;
            ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
            mDecoder->UpdateEstimatedMediaDuration(duration);
        }
    }

    *aNumBytes = totalBytes;

    // We will have read some data in the last iteration iff we filled the buffer.
    // XXX Maybe return a better value than NS_ERROR_FAILURE?
    return numBytes ? NS_OK : NS_ERROR_FAILURE;
}

void GStreamerReader::ReadAndPushData(guint aLength)
{
  MediaResource* resource = mDecoder->GetResource();
  NS_ASSERTION(resource, "Decoder has no media resource");
  int64_t offset1 = resource->Tell();
  unused << offset1;
  nsresult rv = NS_OK;

  GstBuffer* buffer = gst_buffer_new_and_alloc(aLength);
#if GST_VERSION_MAJOR >= 1
  GstMapInfo info;
  gst_buffer_map(buffer, &info, GST_MAP_WRITE);
  guint8 *data = info.data;
#else
  guint8* data = GST_BUFFER_DATA(buffer);
#endif
  uint32_t size = 0, bytesRead = 0;
  while(bytesRead < aLength) {
    rv = resource->Read(reinterpret_cast<char*>(data + bytesRead),
        aLength - bytesRead, &size);
    if (NS_FAILED(rv) || size == 0)
      break;

    bytesRead += size;
  }

  int64_t offset2 = resource->Tell();
  unused << offset2;

#if GST_VERSION_MAJOR >= 1
  gst_buffer_unmap(buffer, &info);
  gst_buffer_set_size(buffer, bytesRead);
#else
  GST_BUFFER_SIZE(buffer) = bytesRead;
#endif

  GstFlowReturn ret = gst_app_src_push_buffer(mSource, gst_buffer_ref(buffer));
  if (ret != GST_FLOW_OK) {
    LOG(PR_LOG_ERROR, "ReadAndPushData push ret %s(%d)", gst_flow_get_name(ret), ret);
  }

  if (NS_FAILED(rv)) {
    /* Terminate the stream if there is an error in reading */
    LOG(PR_LOG_ERROR, "ReadAndPushData read error, rv=%x", rv);
    gst_app_src_end_of_stream(mSource);
  } else if (bytesRead < aLength) {
    /* If we read less than what we wanted, we reached the end */
    LOG(PR_LOG_WARNING, "ReadAndPushData read underflow, "
        "bytesRead=%u, aLength=%u, offset(%lld,%lld)",
        bytesRead, aLength, offset1, offset2);
    gst_app_src_end_of_stream(mSource);
  }

  gst_buffer_unref(buffer);

  /* Ensure offset change is consistent in this function.
   * If there are other stream operations on another thread at the same time,
   * it will disturb the GStreamer state machine.
   */
  MOZ_ASSERT(offset1 + bytesRead == offset2);
}