⬥ ID3 encoding/decoding library in Go ⬥
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package id3ed
import (
"bytes"
"fmt"
"io"
"strconv"
)
// https://id3.org/ID3v1 - documentation
const ID3V1SIZE int = 128
type ID3v1Tags struct {
SongName string
Artist string
Album string
Year int
Comment string
Genre int
}
// Retrieves ID3v1 field values of provided io.ReadSeeker (usually a file)
func GetID3v1Tags(rs io.ReadSeeker) (*ID3v1Tags, error) {
// set reader to the last 128 bytes
_, err := rs.Seek(-int64(ID3V1SIZE), io.SeekEnd)
if err != nil {
return nil, fmt.Errorf("could not seek: %s", err)
}
tag, err := read(rs, 3)
if err != nil {
return nil, err
}
if !bytes.Equal(tag, []byte("TAG")) {
// no TAG, given file does not use ID3v1
return nil, fmt.Errorf("does not use ID3v1")
}
songname, err := read(rs, 30)
if err != nil {
return nil, err
}
artist, err := read(rs, 30)
if err != nil {
return nil, err
}
album, err := read(rs, 30)
if err != nil {
return nil, err
}
yearBytes, err := read(rs, 4)
if err != nil {
return nil, err
}
year, err := strconv.Atoi(string(yearBytes))
if err != nil {
return nil, fmt.Errorf("could not convert yearbytes into int: %s", err)
}
comment, err := read(rs, 30)
if err != nil {
return nil, err
}
genreByte, err := read(rs, 1)
if err != nil {
return nil, err
}
// genre is one byte by specification
genre := int(genreByte[0])
return &ID3v1Tags{
SongName: string(songname),
Artist: string(artist),
Album: string(album),
Year: year,
Comment: string(comment),
Genre: genre,
}, nil
}
func (t *ID3v1Tags) GetSongName() string {
return t.SongName
}
func (t *ID3v1Tags) GetArtist() string {
return t.Artist
}
func (t *ID3v1Tags) GetAlbum() string {
return t.Album
}
func (t *ID3v1Tags) GetYear() int {
return t.Year
}
func (t *ID3v1Tags) GetComment() string {
return t.Comment
}
func (t *ID3v1Tags) GetGenre() int {
return t.Genre
}