⬥ ID3 encoding/decoding library in Go ⬥
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package v1
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"os"
"github.com/Unbewohnte/id3ed/util"
)
// Writes given ID3v1.0 tags to given io.WriteSeeker.
// NOTE: will not remove already existing ID3v1 tag if it`s present,
// use ⁕WriteToFile⁕ method if you`re working with REAL mp3 files !!!
func (tags *ID3v1Tags) Write(dst io.WriteSeeker) error {
dst.Seek(0, io.SeekEnd)
// TAG
_, err := dst.Write([]byte(ID3v1IDENTIFIER))
if err != nil {
return fmt.Errorf("could not write to writer: %s", err)
}
// Song name
err = util.WriteToExtent(dst, []byte(tags.SongName), 30)
if err != nil {
return fmt.Errorf("could not write to writer: %s", err)
}
// Artist
err = util.WriteToExtent(dst, []byte(tags.Artist), 30)
if err != nil {
return fmt.Errorf("could not write to writer: %s", err)
}
// Album
err = util.WriteToExtent(dst, []byte(tags.Album), 30)
if err != nil {
return fmt.Errorf("could not write to writer: %s", err)
}
// Year
err = util.WriteToExtent(dst, []byte(fmt.Sprint(tags.Year)), 4)
if err != nil {
return fmt.Errorf("could not write to writer: %s", err)
}
// Comment
err = util.WriteToExtent(dst, []byte(tags.Comment), 30)
if err != nil {
return fmt.Errorf("could not write to writer: %s", err)
}
// Genre
genreCode := util.GetKey(id3v1genres, tags.Genre)
if genreCode == -1 {
// if no genre found - encode genre code as 255
genreCode = ID3v1INVALIDGENRE
}
genrebyte := make([]byte, 1)
binary.PutVarint(genrebyte, int64(genreCode))
_, err = dst.Write(genrebyte)
if err != nil {
return fmt.Errorf("could not write to writer: %s", err)
}
return nil
}
// Checks for existing ID3v1 tag in file, if present - removes it and replaces with provided tags
func (tags *ID3v1Tags) WriteToFile(f *os.File) error {
defer f.Close()
// check for existing ID3v1 tag
f.Seek(-int64(ID3v1SIZE), io.SeekEnd)
tag, err := util.Read(f, 3)
if err != nil {
return err
}
if !bytes.Equal(tag, []byte(ID3v1IDENTIFIER)) {
// no existing tag, just write given tags
err = tags.Write(f)
if err != nil {
return err
}
return nil
}
// does contain ID3v1 tag. Removing it
fStats, err := f.Stat()
if err != nil {
return fmt.Errorf("cannot get file stats: %s", err)
}
err = f.Truncate(fStats.Size() - int64(ID3v1SIZE))
if err != nil {
return fmt.Errorf("could not truncate file %s", err)
}
// writing new tags
err = tags.Write(f)
if err != nil {
return fmt.Errorf("could not write to writer: %s", err)
}
return nil
}