meta: simplify parseCueSheet by refactoring
Fixes lint issue reported by gocyclo:
meta/cuesheet.go:30:1: cyclomatic complexity 37 of func `(*Block).parseCueSheet` is high (> 30) (gocyclo)
func (block *Block) parseCueSheet() error {
^
Fixes #25.
This commit is contained in:
mewmew
parent
46e9cd6b14
commit
10505c0392
207
meta/cuesheet.go
207
meta/cuesheet.go
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@ -34,9 +34,10 @@ func (block *Block) parseCueSheet() error {
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if err != nil {
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return unexpected(err)
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}
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cs := new(CueSheet)
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cs := &CueSheet{
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MCN: stringFromSZ(buf),
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}
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block.Body = cs
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cs.MCN = stringFromSZ(buf)
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// 64 bits: NLeadInSamples.
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if err = binary.Read(block.lr, binary.BigEndian, &cs.NLeadInSamples); err != nil {
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@ -45,7 +46,7 @@ func (block *Block) parseCueSheet() error {
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// 1 bit: IsCompactDisc.
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var x uint8
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if err = binary.Read(block.lr, binary.BigEndian, &x); err != nil {
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if err := binary.Read(block.lr, binary.BigEndian, &x); err != nil {
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return unexpected(err)
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}
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// mask = 10000000
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@ -60,14 +61,13 @@ func (block *Block) parseCueSheet() error {
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}
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lr := io.LimitReader(block.lr, 258)
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zr := zeros{r: lr}
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_, err = io.Copy(ioutil.Discard, zr)
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if err != nil {
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if _, err := io.Copy(ioutil.Discard, zr); err != nil {
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return err
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}
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// Parse cue sheet tracks.
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// 8 bits: (number of tracks)
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if err = binary.Read(block.lr, binary.BigEndian, &x); err != nil {
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if err := binary.Read(block.lr, binary.BigEndian, &x); err != nil {
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return unexpected(err)
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}
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if x < 1 {
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@ -81,111 +81,122 @@ func (block *Block) parseCueSheet() error {
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// track.
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uniq := make(map[uint8]struct{})
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for i := range cs.Tracks {
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// 64 bits: Offset.
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track := &cs.Tracks[i]
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if err = binary.Read(block.lr, binary.BigEndian, &track.Offset); err != nil {
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return unexpected(err)
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if err := block.parseTrack(cs, i, uniq); err != nil {
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return err
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}
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if cs.IsCompactDisc && track.Offset%588 != 0 {
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return fmt.Errorf("meta.Block.parseCueSheet: CD-DA track offset (%d) must be evenly divisible by 588", track.Offset)
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}
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return nil
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}
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// parseTrack parses the i:th cue sheet track, and ensures that its track number
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// is unique.
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func (block *Block) parseTrack(cs *CueSheet, i int, uniq map[uint8]struct{}) error {
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track := &cs.Tracks[i]
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// 64 bits: Offset.
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if err := binary.Read(block.lr, binary.BigEndian, &track.Offset); err != nil {
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return unexpected(err)
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}
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if cs.IsCompactDisc && track.Offset%588 != 0 {
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return fmt.Errorf("meta.Block.parseCueSheet: CD-DA track offset (%d) must be evenly divisible by 588", track.Offset)
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}
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// 8 bits: Num.
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if err := binary.Read(block.lr, binary.BigEndian, &track.Num); err != nil {
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return unexpected(err)
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}
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if _, ok := uniq[track.Num]; ok {
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return fmt.Errorf("meta.Block.parseCueSheet: duplicated track number %d", track.Num)
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}
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uniq[track.Num] = struct{}{}
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if track.Num == 0 {
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return errors.New("meta.Block.parseCueSheet: invalid track number (0)")
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}
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isLeadOut := i == len(cs.Tracks)-1
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if cs.IsCompactDisc {
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if !isLeadOut {
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if track.Num >= 100 {
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return fmt.Errorf("meta.Block.parseCueSheet: CD-DA track number (%d) exceeds 99", track.Num)
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}
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} else {
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if track.Num != 170 {
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return fmt.Errorf("meta.Block.parseCueSheet: invalid lead-out CD-DA track number; expected 170, got %d", track.Num)
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}
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}
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} else {
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if isLeadOut && track.Num != 255 {
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return fmt.Errorf("meta.Block.parseCueSheet: invalid lead-out track number; expected 255, got %d", track.Num)
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}
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}
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// 12 bytes: ISRC.
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buf, err := readBytes(block.lr, 12)
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if err != nil {
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return unexpected(err)
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}
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track.ISRC = stringFromSZ(buf)
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// 1 bit: IsAudio.
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var x uint8
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if err = binary.Read(block.lr, binary.BigEndian, &x); err != nil {
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return unexpected(err)
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}
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// mask = 10000000
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if x&0x80 == 0 {
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track.IsAudio = true
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}
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// 1 bit: HasPreEmphasis.
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// mask = 01000000
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if x&0x40 != 0 {
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track.HasPreEmphasis = true
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}
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// 6 bits and 13 bytes: reserved.
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// mask = 00111111
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if x&0x3F != 0 {
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return ErrInvalidPadding
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}
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lr := io.LimitReader(block.lr, 13)
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zr := zeros{r: lr}
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_, err = io.Copy(ioutil.Discard, zr)
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if err != nil {
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return err
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}
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// Parse indicies.
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// 8 bits: (number of indicies)
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if err = binary.Read(block.lr, binary.BigEndian, &x); err != nil {
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return unexpected(err)
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}
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if x < 1 {
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if !isLeadOut {
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return errors.New("meta.Block.parseCueSheet: at least one track index required")
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}
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// Lead-out track has no track indices to parse; return early.
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return nil
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}
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track.Indicies = make([]CueSheetTrackIndex, x)
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for i := range track.Indicies {
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index := &track.Indicies[i]
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// 64 bits: Offset.
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if err = binary.Read(block.lr, binary.BigEndian, &index.Offset); err != nil {
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return unexpected(err)
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}
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// 8 bits: Num.
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if err = binary.Read(block.lr, binary.BigEndian, &track.Num); err != nil {
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if err = binary.Read(block.lr, binary.BigEndian, &index.Num); err != nil {
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return unexpected(err)
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}
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if _, ok := uniq[track.Num]; ok {
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return fmt.Errorf("meta.Block.parseCueSheet: duplicated track number %d", track.Num)
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}
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uniq[track.Num] = struct{}{}
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if track.Num == 0 {
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return errors.New("meta.Block.parseCueSheet: invalid track number (0)")
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}
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isLeadOut := i == len(cs.Tracks)-1
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if cs.IsCompactDisc {
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if !isLeadOut {
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if track.Num >= 100 {
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return fmt.Errorf("meta.Block.parseCueSheet: CD-DA track number (%d) exceeds 99", track.Num)
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}
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} else {
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if track.Num != 170 {
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return fmt.Errorf("meta.Block.parseCueSheet: invalid lead-out CD-DA track number; expected 170, got %d", track.Num)
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}
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}
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} else {
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if isLeadOut && track.Num != 255 {
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return fmt.Errorf("meta.Block.parseCueSheet: invalid lead-out track number; expected 255, got %d", track.Num)
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}
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}
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// 12 bytes: ISRC.
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buf, err = readBytes(block.lr, 12)
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if err != nil {
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return unexpected(err)
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}
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track.ISRC = stringFromSZ(buf)
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// 1 bit: IsAudio.
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if err = binary.Read(block.lr, binary.BigEndian, &x); err != nil {
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return unexpected(err)
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}
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// mask = 10000000
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if x&0x80 == 0 {
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track.IsAudio = true
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}
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// 1 bit: HasPreEmphasis.
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// mask = 01000000
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if x&0x40 != 0 {
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track.HasPreEmphasis = true
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}
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// 6 bits and 13 bytes: reserved.
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// mask = 00111111
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if x&0x3F != 0 {
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return ErrInvalidPadding
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}
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lr = io.LimitReader(block.lr, 13)
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// 3 bytes: reserved.
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lr = io.LimitReader(block.lr, 3)
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zr = zeros{r: lr}
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_, err = io.Copy(ioutil.Discard, zr)
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if err != nil {
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return err
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}
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// Parse indicies.
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// 8 bits: (number of indicies)
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if err = binary.Read(block.lr, binary.BigEndian, &x); err != nil {
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return unexpected(err)
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}
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if x < 1 {
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if !isLeadOut {
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return errors.New("meta.Block.parseCueSheet: at least one track index required")
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}
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continue
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}
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track.Indicies = make([]CueSheetTrackIndex, x)
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for i := range track.Indicies {
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index := &track.Indicies[i]
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// 64 bits: Offset.
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if err = binary.Read(block.lr, binary.BigEndian, &index.Offset); err != nil {
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return unexpected(err)
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}
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// 8 bits: Num.
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if err = binary.Read(block.lr, binary.BigEndian, &index.Num); err != nil {
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return unexpected(err)
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}
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// 3 bytes: reserved.
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lr = io.LimitReader(block.lr, 3)
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zr = zeros{r: lr}
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_, err = io.Copy(ioutil.Discard, zr)
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if err != nil {
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return err
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}
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}
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}
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return nil
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}
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