Exemplo n.º 1
0
Arquivo: flac.go Projeto: shazow/mog
// Parse creates a new Stream for accessing the metadata blocks and audio
// samples of r. It reads and parses the FLAC signature and all metadata blocks.
//
// Call Stream.Next to parse the frame header of the next audio frame, and call
// Stream.ParseNext to parse the entire next frame including audio samples.
func Parse(r io.Reader) (stream *Stream, err error) {
	// Verify FLAC signature and parse the StreamInfo metadata block.
	br := bufio.NewReader(r)
	stream = &Stream{r: br}
	isLast, err := stream.parseStreamInfo()
	if err != nil {
		return nil, err
	}

	// Parse the remaining metadata blocks.
	for !isLast {
		block, err := meta.Parse(br)
		if err != nil {
			if err != meta.ErrReservedType {
				return stream, err
			}
			// Skip the body of unknown (reserved) metadata blocks, as stated by
			// the specification.
			//
			// ref: https://www.xiph.org/flac/format.html#format_overview
			err = block.Skip()
			if err != nil {
				return stream, err
			}
		}
		stream.Blocks = append(stream.Blocks, block)
		isLast = block.IsLast
	}

	return stream, nil
}
Exemplo n.º 2
0
Arquivo: flac.go Projeto: shazow/mog
// parseStreamInfo verifies the signature which marks the beginning of a FLAC
// stream, and parses the StreamInfo metadata block. It returns a boolean value
// which specifies if the StreamInfo block was the last metadata block of the
// FLAC stream.
func (stream *Stream) parseStreamInfo() (isLast bool, err error) {
	// Verify FLAC signature.
	r := stream.r
	var buf [4]byte
	_, err = io.ReadFull(r, buf[:])
	if err != nil {
		return false, err
	}
	if !bytes.Equal(buf[:], signature) {
		return false, fmt.Errorf("flac.parseStreamInfo: invalid FLAC signature; expected %q, got %q", signature, buf)
	}

	// Parse StreamInfo metadata block.
	block, err := meta.Parse(r)
	if err != nil {
		return false, err
	}
	si, ok := block.Body.(*meta.StreamInfo)
	if !ok {
		return false, fmt.Errorf("flac.parseStreamInfo: incorrect type of first metadata block; expected *meta.StreamInfo, got %T", si)
	}
	stream.Info = si
	return block.IsLast, nil
}