func (editor *OggTagEditor) WriteTag(src, dst string, tag Tag) error {
err := editor.readFile(src)
if err != nil {
return err
}
idPage, commentPages, restData := editor.splitFileData(editor.file)
newCommentPages, newSetupPages, numberOfPages := editor.makeNewPages(commentPages, tag)
newPrefix := make([]byte, len(idPage)+len(newCommentPages)+len(newSetupPages))
copy(newPrefix, idPage)
copy(newPrefix[len(idPage):], newCommentPages)
copy(newPrefix[len(idPage)+len(newCommentPages):], newSetupPages)
// fix page numbers and CRCs
sequence := numberOfPages + 1
data := restData
for len(data) > oggPageHeaderSize {
pageSize := editor.getPageSize(data)
utils.WriteInt32Le(sequence, data[18:22]) // number
utils.WriteUint32Le(0, data[22:26]) // zero CRC
utils.WriteUint32Le(editor.crc(data[:pageSize]), data[22:26]) // CRC
sequence++
data = data[pageSize:]
}
return ioutil.WriteFile(dst, append(newPrefix, restData...), 0666)
}
func (editor *OggTagEditor) packTagDataIntoFrames(bitstream, sequence int, tagData []byte) ([]byte, int) {
totalTagSize := len(tagData)
if totalTagSize == 0 {
return nil, 0
}
tagSize := 0
size := 0
pages := 0
result := make([]byte, totalTagSize+282*(totalTagSize/maxFrameDataSize+1))
for tagSize < totalTagSize {
headerSize, dataSize := editor.fillHeader(result[size:], bitstream, sequence+pages, totalTagSize-tagSize)
pages++
if tagSize != 0 {
result[size+len(oggPageMagic)+1] = headerTypeContinue
}
size += headerSize
copy(result[size:size+dataSize], tagData[:dataSize])
size += dataSize
tagSize += dataSize
tagData = tagData[dataSize:]
checksum := editor.crc(result[size-headerSize-dataSize : size])
utils.WriteUint32Le(checksum, result[size-headerSize-dataSize+22:size-headerSize-dataSize+26])
}
return result[:size], pages
}