ogg: support comment header packets spanning pages (#57)

* ogg: support comment header packets spanning pages

* ogg: add test for multipage comment header

* ogg: cleaner buffer initialization

Co-Authored-By: David Howden <dhowden@gmail.com>
This commit is contained in:
w1ck3dg0ph3r 2019-11-22 14:23:40 +03:00 committed by David Howden
parent f644c14784
commit 73beae5008
3 changed files with 89 additions and 40 deletions

100
ogg.go
View File

@ -5,6 +5,7 @@
package tag
import (
"bytes"
"errors"
"io"
)
@ -61,34 +62,17 @@ func ReadOGGTags(r io.ReadSeeker) (Metadata, error) {
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)
// Read comment header packet. May include setup header packet, if it is on the
// same page. First audio packet is guaranteed to be on the separate page.
// See https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-132000A.2
ch, err := readPackets(r)
if err != nil {
return nil, err
}
if oggs != "OggS" {
return nil, errors.New("expected 'OggS'")
}
chr := bytes.NewReader(ch)
// Skip page 2 header, same as line 30
_, err = r.Seek(22, io.SeekCurrent)
if err != nil {
return nil, err
}
nS, err = readInt(r, 1)
if err != nil {
return nil, err
}
_, err = r.Seek(int64(nS), io.SeekCurrent)
if err != nil {
return nil, err
}
// Packet type is comment, type 3
t, err = readInt(r, 1)
// First packet type is comment, type 3
t, err = readInt(chr, 1)
if err != nil {
return nil, err
}
@ -97,7 +81,7 @@ func ReadOGGTags(r io.ReadSeeker) (Metadata, error) {
}
// Seek and discard 6 bytes from common header
_, err = r.Seek(6, io.SeekCurrent)
_, err = chr.Seek(6, io.SeekCurrent)
if err != nil {
return nil, err
}
@ -106,10 +90,74 @@ func ReadOGGTags(r io.ReadSeeker) (Metadata, error) {
newMetadataVorbis(),
}
err = m.readVorbisComment(r)
err = m.readVorbisComment(chr)
return m, err
}
// readPackets reads vorbis header packets from contiguous ogg pages in ReadSeeker.
// The pages are considered contiguous, if the first lacing value in second
// page's segment table continues rather than begins a packet. This is indicated
// by setting header_type_flag 0x1 (continued packet).
// See https://www.xiph.org/ogg/doc/framing.html on packets spanning pages.
func readPackets(r io.ReadSeeker) ([]byte, error) {
buf := &bytes.Buffer{}
firstPage := true
for {
// Read capture pattern
oggs, err := readString(r, 4)
if err != nil {
return nil, err
}
if oggs != "OggS" {
return nil, errors.New("expected 'OggS'")
}
// Read page header
head, err := readBytes(r, 22)
if err != nil {
return nil, err
}
headerTypeFlag := head[1]
continuation := headerTypeFlag&0x1 > 0
if !(firstPage || continuation) {
// Rewind to the beginning of the page
_, err = r.Seek(-26, io.SeekCurrent)
if err != nil {
return nil, err
}
break
}
firstPage = false
// Read the number of segments
nS, err := readInt(r, 1)
if err != nil {
return nil, err
}
// Read segment table
segments, err := readBytes(r, nS)
if err != nil {
return nil, err
}
// Calculate remaining page size
pageSize := 0
for i := 0; i < nS; i++ {
pageSize += int(segments[i])
}
_, err = io.CopyN(buf, r, int64(pageSize))
if err != nil {
return nil, err
}
}
return buf.Bytes(), nil
}
type metadataOGG struct {
*metadataVorbis
}

View File

@ -54,20 +54,21 @@ var mp3id3v11Metadata = testMetadata{
func TestReadFrom(t *testing.T) {
testdata := map[string]testMetadata{
"with_tags/sample.flac": fullMetadata,
"with_tags/sample.id3v11.mp3": mp3id3v11Metadata,
"with_tags/sample.id3v22.mp3": fullMetadata,
"with_tags/sample.id3v23.mp3": fullMetadata,
"with_tags/sample.id3v24.mp3": fullMetadata,
"with_tags/sample.m4a": fullMetadata,
"with_tags/sample.mp4": fullMetadata,
"with_tags/sample.ogg": fullMetadata,
"with_tags/sample.dsf": fullMetadata,
"without_tags/sample.flac": emptyMetadata,
"without_tags/sample.m4a": emptyMetadata,
"without_tags/sample.mp3": emptyMetadata,
"without_tags/sample.mp4": emptyMetadata,
"without_tags/sample.ogg": emptyMetadata,
"with_tags/sample.flac": fullMetadata,
"with_tags/sample.id3v11.mp3": mp3id3v11Metadata,
"with_tags/sample.id3v22.mp3": fullMetadata,
"with_tags/sample.id3v23.mp3": fullMetadata,
"with_tags/sample.id3v24.mp3": fullMetadata,
"with_tags/sample.m4a": fullMetadata,
"with_tags/sample.mp4": fullMetadata,
"with_tags/sample.ogg": fullMetadata,
"with_tags/sample.multipage.ogg": fullMetadata,
"with_tags/sample.dsf": fullMetadata,
"without_tags/sample.flac": emptyMetadata,
"without_tags/sample.m4a": emptyMetadata,
"without_tags/sample.mp3": emptyMetadata,
"without_tags/sample.mp4": emptyMetadata,
"without_tags/sample.ogg": emptyMetadata,
}
for path, metadata := range testdata {

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