Merge branch 'Simon-L-master'

This commit is contained in:
David Howden 2015-05-24 09:50:28 +10:00
commit e5e85d7360
2 changed files with 121 additions and 0 deletions

118
ogg.go Normal file
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@ -0,0 +1,118 @@
// Copyright 2015, David Howden
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package tag
import (
"errors"
"io"
"os"
)
const (
idType int = 1
commentType = 3
)
// ReadOGGTags reads OGG metadata from the io.ReadSeeker, returning the resulting
// metadata in a Metadata implementation, or non-nil error if there was a problem.
// See http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html and http://www.xiph.org/ogg/doc/framing.html for details
// TODO: Needs a more generic return type than "metadataFLAC" and the "FLAC" format is not as obvious as "Vorbis comment"
func ReadOGGTags(r io.ReadSeeker) (Metadata, error) {
_, err := r.Seek(0, os.SEEK_SET)
if err != nil {
return nil, err
}
oggs, err := readString(r, 4)
if err != nil {
return nil, err
}
if oggs != "OggS" {
return nil, errors.New("expected 'OggS'")
}
// Skip 22 bytes of Page header to read page_segments length byte at position 26
// See http://www.xiph.org/ogg/doc/framing.html
_, err = r.Seek(22, os.SEEK_CUR)
if err != nil {
return nil, err
}
nS, err := readInt(r, 1)
if err != nil {
return nil, err
}
// Seek and discard the segments
_, err = r.Seek(int64(nS), os.SEEK_CUR)
if err != nil {
return nil, err
}
// First packet type is identification, type 1
t, err := readInt(r, 1)
if err != nil {
return nil, err
}
if t != idType {
return nil, errors.New("expected 'vorbis' identification type 1")
}
// Seek and discard 29 bytes from common and identification header
// See http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-610004.2
_, err = r.Seek(29, os.SEEK_CUR)
if err != nil {
return nil, err
}
// Beginning of a new page. Comment packet is on a separate page
// See http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-132000A.2
oggs, err = readString(r, 4)
if err != nil {
return nil, err
}
if oggs != "OggS" {
return nil, errors.New("expected 'OggS'")
}
// Skip page 2 header, same as line 30
_, err = r.Seek(22, os.SEEK_CUR)
if err != nil {
return nil, err
}
nS, err = readInt(r, 1)
if err != nil {
return nil, err
}
_, err = r.Seek(int64(nS), os.SEEK_CUR)
if err != nil {
return nil, err
}
// Packet type is comment, type 3
t, err = readInt(r, 1)
if err != nil {
return nil, err
}
if t != commentType {
return nil, errors.New("expected 'vorbis' comment type 3")
}
// Seek and discard 6 bytes from common header
_, err = r.Seek(6, os.SEEK_CUR)
if err != nil {
return nil, err
}
m := &metadataFLAC{
c: make(map[string]string),
}
err = m.readVorbisComment(r)
return m, err
}

3
tag.go
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@ -29,6 +29,9 @@ func ReadFrom(r io.ReadSeeker) (Metadata, error) {
case string(b[0:4]) == "fLaC":
return ReadFLACTags(r)
case string(b[0:4]) == "OggS":
return ReadOGGTags(r)
case string(b[4:11]) == "ftypM4A":
return ReadAtoms(r)