S.O.N.G/flacgo
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flac: add nil return in searchFromStart to fix build

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Also, rename sample to sampleNum for consistency.

Use line80 comments like it is the summer of 1969.
This commit is contained in:
Robin Eklind 2021-01-28 00:32:43 +01:00
parent 11466d8af8
commit 48c2491b7c
1 changed files with 26 additions and 17 deletions
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43
flac.go
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@ -49,12 +49,14 @@ type Stream struct {
// Zero or more metadata blocks.
Blocks []*meta.Block
// seekTable contains one or more pre-calculated audio frame seek points of the stream; nil if uninitialized.
// seekTable contains one or more pre-calculated audio frame seek points of
// the stream; nil if uninitialized.
seekTable *meta.SeekTable
// seekTableSize determines how many seek points the seekTable should have if the flac file does not include one
// in the metadata.
// seekTableSize determines how many seek points the seekTable should have if
// the flac file does not include one in the metadata.
seekTableSize int
// dataStart is the offset of the first frame header since SeekPoint.Offset is relative to this position.
// dataStart is the offset of the first frame header since SeekPoint.Offset
// is relative to this position.
dataStart int64
// Underlying io.Reader.
@ -93,9 +95,9 @@ func New(r io.Reader) (stream *Stream, err error) {
return stream, nil
}
// NewSeek returns a Stream that has seeking enabled. The incoming
// io.ReadSeeker will not be buffered, which might result in performance issues.
// Using an in-memory buffer like *bytes.Reader should work well.
// NewSeek returns a Stream that has seeking enabled. The incoming io.ReadSeeker
// will not be buffered, which might result in performance issues. Using an
// in-memory buffer like *bytes.Reader should work well.
func NewSeek(rs io.ReadSeeker) (stream *Stream, err error) {
stream = &Stream{r: rs, seekTableSize: defaultSeekTableSize}
@ -130,7 +132,8 @@ var (
// flacSignature marks the beginning of a FLAC stream.
flacSignature = []byte("fLaC")
// id3Signature marks the beginning of an ID3 stream, used to skip over ID3 data.
// id3Signature marks the beginning of an ID3 stream, used to skip over ID3
// data.
id3Signature = []byte("ID3")
// ErrNoSeeker reports that flac.NewSeek was called with an io.Reader not
@ -344,31 +347,37 @@ func (stream *Stream) Seek(sampleNum uint64) (uint64, error) {
return 0, err
}
if frame.SampleNumber()+uint64(frame.BlockSize) >= sampleNum {
// Restore seek offset to the start of the frame containing the specified sample number.
// Restore seek offset to the start of the frame containing the
// specified sample number.
_, err := rs.Seek(offset, io.SeekStart)
return frame.SampleNumber(), err
}
}
}
// TODO(_): Utilize binary search.
// TODO(_): Utilize binary search in searchFromStart.
//
func (stream *Stream) searchFromStart(sample uint64) (meta.SeekPoint, error) {
// searchFromStart searches for the given sample number from the start of the
// seek table and returns the last seek point containing the sample number. If
// no seek point contains the sample number, the last seek point preceding the
// sample number is returned. If the sample number is lower than the first seek
// point, the first seek point is returned.
func (stream *Stream) searchFromStart(sampleNum uint64) (meta.SeekPoint, error) {
if len(stream.seekTable.Points) == 0 {
return meta.SeekPoint{}, ErrNoSeektable
}
prev := stream.seekTable.Points[0]
for _, p := range stream.seekTable.Points {
if p.SampleNum+uint64(p.NSamples) >= sample {
if p.SampleNum+uint64(p.NSamples) >= sampleNum {
return prev, nil
}
prev = p
}
return prev
return prev, nil
}
// makeSeekTable creates a seek table with seek points to each frame of the FLAC stream.
// makeSeekTable creates a seek table with seek points to each frame of the FLAC
// stream.
func (stream *Stream) makeSeekTable() (err error) {
rs, ok := stream.r.(io.ReadSeeker)
if !ok {
@ -390,7 +399,7 @@ func (stream *Stream) makeSeekTable() (err error) {
var points []meta.SeekPoint
for {
// Record seek offset to start of frame.
o, err := rs.Seek(0, io.SeekCurrent)
off, err := rs.Seek(0, io.SeekCurrent)
if err != nil {
return err
}
@ -403,7 +412,7 @@ func (stream *Stream) makeSeekTable() (err error) {
}
points = append(points, meta.SeekPoint{
SampleNum: sampleNum,
Offset: uint64(o - stream.dataStart),
Offset: uint64(off - stream.dataStart),
NSamples: f.BlockSize,
})