⬥ ID3 encoding/decoding library in Go ⬥
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128 lines
2.2 KiB

package id3ed
import (
"bytes"
"fmt"
"io"
"strconv"
)
type ID3v11Tags struct {
SongName string
Artist string
Album string
Year int
Comment string
Track int
Genre string
}
// Retrieves ID3v1.1 field values of provided io.ReadSeeker (usually a file)
func GetID3v11Tags(rs io.ReadSeeker) (*ID3v11Tags, 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: expected %s; got %s", "TAG", tag)
}
songname, err := readToString(rs, 30)
if err != nil {
return nil, err
}
artist, err := readToString(rs, 30)
if err != nil {
return nil, err
}
album, err := readToString(rs, 30)
if err != nil {
return nil, err
}
yearStr, err := readToString(rs, 4)
if err != nil {
return nil, err
}
year, err := strconv.Atoi(yearStr)
if err != nil {
return nil, fmt.Errorf("could not convert yearbytes into int: %s", err)
}
comment, err := readToString(rs, 28)
if err != nil {
return nil, err
}
// skip 1 null byte
_, err = read(rs, 1)
if err != nil {
return nil, err
}
trackByte, err := read(rs, 1)
if err != nil {
return nil, err
}
// track is one byte by specification
track := int(trackByte[0])
genreByte, err := read(rs, 1)
if err != nil {
return nil, err
}
// genre is one byte by specification
genre, exists := id3v1genres[int(genreByte[0])]
if !exists {
genre = ""
}
return &ID3v11Tags{
SongName: songname,
Artist: artist,
Album: album,
Year: year,
Comment: comment,
Track: track,
Genre: genre,
}, nil
}
func (t *ID3v11Tags) GetSongName() string {
return t.SongName
}
func (t *ID3v11Tags) GetArtist() string {
return t.Artist
}
func (t *ID3v11Tags) GetAlbum() string {
return t.Album
}
func (t *ID3v11Tags) GetYear() int {
return t.Year
}
func (t *ID3v11Tags) GetComment() string {
return t.Comment
}
func (t *ID3v11Tags) GetTrack() int {
return t.Track
}
func (t *ID3v11Tags) GetGenre() string {
return t.Genre
}