func getUnsupportedVorbisTags(data []byte) ([]byte, int) {
result := make([]byte, len(data))
fields := 0
size := 0
numberOfFields := utils.ReadInt32Le(data[0:4])
data = data[4:]
for i := 0; i < numberOfFields; i++ {
fieldSize := utils.ReadInt32Le(data[0:4])
if len(data) < fieldSize+4 {
break
}
pos := bytes.IndexByte(data[4:4+fieldSize], 0x3d)
if pos == -1 {
break
}
fieldName := strings.ToUpper(string(data[4 : 4+pos]))
switch fieldName {
case "TITLE", "ARTIST", "ALBUM", "TRACKNUMBER", "DATE", "GENRE", "METADATA_BLOCK_PICTURE":
break
default:
copy(result[size:size+4+fieldSize], data[:4+fieldSize])
fields++
size += 4 + fieldSize
}
data = data[4+fieldSize:]
}
return result[:size], fields
}
func (editor *OggTagEditor) makeNewPages(existingCommentPages []byte, tag Tag) ([]byte, []byte, int) {
// bitstream number
var bitstream int = 31013
if len(existingCommentPages) > oggPageHeaderSize {
bitstream = utils.ReadInt32Le(existingCommentPages[14:18])
}
commentHeader, existingTagData, setupHeader := editor.splitCommentPages(existingCommentPages)
if len(commentHeader) == 0 {
commentHeader = make([]byte, 1+len(oggHeaderMagic)+4)
commentHeader[0] = 3
copy(commentHeader[1:1+len(oggHeaderMagic)], oggHeaderMagic)
utils.WriteInt32Le(0, commentHeader[len(oggHeaderMagic):len(oggHeaderMagic)+4])
}
unsupportedTagData, unsupportedFields := getUnsupportedVorbisTags(existingTagData)
newTagData, totalFields := serializeVorbisTag(tag, unsupportedFields)
tagData := make([]byte, len(commentHeader)+4+len(newTagData)+len(unsupportedTagData)+1)
copy(tagData, commentHeader)
utils.WriteInt32Le(totalFields, tagData[len(commentHeader):len(commentHeader)+4])
copy(tagData[len(commentHeader)+4:], newTagData)
copy(tagData[len(commentHeader)+4+len(newTagData):], unsupportedTagData)
tagData[len(tagData)-1] = 1
newCommentHeader, commentPages := editor.packTagDataIntoFrames(bitstream, 1, tagData)
newSetupHeader, setupPages := editor.packTagDataIntoFrames(bitstream, commentPages+1, setupHeader)
return newCommentHeader, newSetupHeader, commentPages + setupPages
}
func (editor *OggTagEditor) splitCommentPages(pages []byte) ([]byte, []byte, []byte) {
var commentHeader []byte = nil
var tagData []byte = nil
var setupHeader []byte = nil
for len(pages) > oggPageHeaderSize {
pageHeaderSize := oggPageHeaderSize + int(pages[oggPageHeaderSize-1])
// it's the 1st page, the one with comment header
if pages[5]&headerTypeContinue == 0 {
if len(pages) < pageHeaderSize+5+len(oggHeaderMagic) {
return nil, nil, nil
}
commentHeaderSize := utils.ReadInt32Le(pages[pageHeaderSize+1+len(oggHeaderMagic) : pageHeaderSize+5+len(oggHeaderMagic)])
if len(pages) < pageHeaderSize+5+len(oggHeaderMagic)+commentHeaderSize {
return nil, nil, nil
}
commentHeader = pages[pageHeaderSize : pageHeaderSize+5+len(oggHeaderMagic)+commentHeaderSize]
pageHeaderSize += 5 + len(oggHeaderMagic) + commentHeaderSize
}
pageSize := editor.getPageSize(pages)
tagData = append(tagData, pages[pageHeaderSize:pageSize]...)
pages = pages[pageSize:]
}
pos := bytes.Index(tagData, []byte(oggHeaderMagic))
if pos != -1 {
setupHeader = tagData[pos-1:]
tagData = tagData[:pos-1]
}
return commentHeader, tagData, setupHeader
}
func (editor *FlacTagEditor) parseCommentBlock(data []byte, tag *Tag) error {
if len(data) < 8 {
return errors.New("no flac comment block to parse")
}
vendorSize := utils.ReadInt32Le(data[4:8])
return parseVorbisTags(data[8+vendorSize:], tag)
}
func parseVorbisTags(data []byte, tag *Tag) error {
if len(data) < 4 {
return errors.New("vorbis data is too short to contain a tag")
}
numberOfFields := utils.ReadInt32Le(data[0:4])
data = data[4:]
for i := 0; i < numberOfFields; i++ {
fieldSize := utils.ReadInt32Le(data[0:4])
if fieldSize+4 <= len(data) {
parseVorbisTagField(data[4:4+fieldSize], tag)
data = data[4+fieldSize:]
}
}
return nil
}
func (editor *FlacTagEditor) makeNewCommentBlock(tag Tag, existingCommentBlock []byte) []byte {
var vendorData []byte = nil
var unsupportedTagData []byte = nil
var unsupportedFields int = 0
if len(existingCommentBlock) >= 8 {
vendorSize := utils.ReadInt32Le(existingCommentBlock[4:8])
vendorData = existingCommentBlock[4 : 8+vendorSize]
unsupportedTagData, unsupportedFields = getUnsupportedVorbisTags(existingCommentBlock[8+vendorSize:])
}
newCommentData, totalFields := serializeVorbisTag(tag, unsupportedFields)
newCommentBlock := make([]byte, 4+len(vendorData)+4+len(newCommentData)+len(unsupportedTagData))
newCommentBlock[0] = commentBlockType
utils.WriteInt24Be(len(newCommentBlock)-4, newCommentBlock[1:4])
copy(newCommentBlock[4:], vendorData)
utils.WriteInt32Le(totalFields, newCommentBlock[4+len(vendorData):8+len(vendorData)])
copy(newCommentBlock[8+len(vendorData):], newCommentData)
copy(newCommentBlock[8+len(vendorData)+len(newCommentData):], unsupportedTagData)
return newCommentBlock
}