96 lines
1.8 KiB
Go
96 lines
1.8 KiB
Go
// Copyright 2015, David Howden
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package tag
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import (
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"errors"
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"io"
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"os"
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)
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// BlockType is a type which represents an enumeration of valid FLAC blocks
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type BlockType byte
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// FLAC block types.
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const (
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StreamInfoBlock BlockType = 0
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PaddingBlock = 1
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ApplicationBlock = 2
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SeektableBlock = 3
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VorbisCommentBlock = 4 // Supported
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CueSheetBlock = 5
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PictureBlock = 6 // Supported
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)
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// ReadFLACTags reads FLAC metadata from the io.ReadSeeker, returning the resulting
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// metadata in a Metadata implementation, or non-nil error if there was a problem.
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func ReadFLACTags(r io.ReadSeeker) (Metadata, error) {
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_, err := r.Seek(0, os.SEEK_SET)
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if err != nil {
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return nil, err
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}
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flac, err := readString(r, 4)
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if err != nil {
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return nil, err
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}
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if flac != "fLaC" {
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return nil, errors.New("expected 'fLaC'")
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}
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m := &metadataFLAC{
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newMetadataVorbis(),
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}
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for {
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last, err := m.readFLACMetadataBlock(r)
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if err != nil {
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return nil, err
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}
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if last {
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break
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}
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}
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return m, nil
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}
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type metadataFLAC struct {
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*metadataVorbis
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}
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func (m *metadataFLAC) readFLACMetadataBlock(r io.ReadSeeker) (last bool, err error) {
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blockHeader, err := readBytes(r, 1)
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if err != nil {
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return
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}
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if getBit(blockHeader[0], 7) {
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blockHeader[0] ^= (1 << 7)
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last = true
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}
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blockLen, err := readInt(r, 3)
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if err != nil {
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return
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}
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switch BlockType(blockHeader[0]) {
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case VorbisCommentBlock:
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err = m.readVorbisComment(r)
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case PictureBlock:
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err = m.readPictureBlock(r)
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default:
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_, err = r.Seek(int64(blockLen), os.SEEK_CUR)
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}
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return
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}
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func (m *metadataFLAC) FileType() FileType {
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return FLAC
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}
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