package v1 import ( "bytes" "fmt" "io" "strconv" "github.com/Unbewohnte/id3ed/util" ) var ErrDoesNotUseID3v1 error = fmt.Errorf("does not use ID3v1") // Retrieves ID3v1 field values of provided io.ReadSeeker (usually a file) func Readv1Tag(rs io.ReadSeeker) (*ID3v1Tag, error) { var tag ID3v1Tag // 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) } // ID identifier, err := util.Read(rs, 3) if err != nil { return nil, err } if !bytes.Equal(identifier, []byte(ID3v1IDENTIFIER)) { // no identifier, given file does not use ID3v1 return nil, ErrDoesNotUseID3v1 } // Songname songname, err := util.ReadToString(rs, 30) if err != nil { return nil, err } tag.SongName = songname // Artist artist, err := util.ReadToString(rs, 30) if err != nil { return nil, err } tag.Artist = artist // Album name album, err := util.ReadToString(rs, 30) if err != nil { return nil, err } tag.Album = album // Year yearStr, err := util.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) } tag.Year = year // Comment and Track comment, err := util.Read(rs, 30) if err != nil { return nil, err } tag.Comment = util.ToStringLossy(comment) tag.Track = 0 var track int = 0 // check if 29th byte is null byte (v1.0 or v1.1) if comment[28] == 0 { // it is v1.1, track number exists track, err = util.ByteToInt(comment[29]) if err != nil { return nil, fmt.Errorf("could not get int from byte: %s", err) } tag.Track = uint8(track) comment = comment[0:28] tag.Comment = util.ToStringLossy(comment) } // Genre genreByte, err := util.Read(rs, 1) if err != nil { return nil, err } genreInt, err := util.ByteToInt(genreByte[0]) if err != nil { return nil, fmt.Errorf("cannot convert bytes to int: %s", err) } genre, exists := id3v1genres[int(genreInt)] if !exists { genre = "" } tag.Genre = genre if track == 0 { tag.version = V1_0 } else { tag.version = V1_1 } return &tag, nil }