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109 lines
2.1 KiB
109 lines
2.1 KiB
package v1 |
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import ( |
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"bytes" |
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"fmt" |
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"io" |
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"strconv" |
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"github.com/Unbewohnte/id3ed/util" |
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) |
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// Retrieves ID3v1 field values of provided io.ReadSeeker (usually a file) |
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func Getv1Tag(rs io.ReadSeeker) (*ID3v1Tag, error) { |
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var tag ID3v1Tag |
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// set reader to the last 128 bytes |
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_, err := rs.Seek(-int64(ID3v1SIZE), io.SeekEnd) |
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if err != nil { |
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return nil, fmt.Errorf("could not seek: %s", err) |
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} |
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// ID |
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identifier, err := util.Read(rs, 3) |
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if err != nil { |
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return nil, err |
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} |
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if !bytes.Equal(identifier, []byte(ID3v1IDENTIFIER)) { |
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// no identifier, given file does not use ID3v1 |
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return nil, fmt.Errorf("does not use ID3v1: expected %s; got %s", ID3v1IDENTIFIER, identifier) |
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} |
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// Songname |
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songname, err := util.ReadToString(rs, 30) |
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if err != nil { |
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return nil, err |
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} |
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tag.SongName = songname |
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// Artist |
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artist, err := util.ReadToString(rs, 30) |
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if err != nil { |
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return nil, err |
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} |
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tag.Artist = artist |
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// Album name |
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album, err := util.ReadToString(rs, 30) |
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if err != nil { |
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return nil, err |
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} |
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tag.Album = album |
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// Year |
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yearStr, err := util.ReadToString(rs, 4) |
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if err != nil { |
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return nil, err |
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} |
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year, err := strconv.Atoi(yearStr) |
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if err != nil { |
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return nil, fmt.Errorf("could not convert yearbytes into int: %s", err) |
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} |
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tag.Year = year |
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// Comment and Track |
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comment, err := util.Read(rs, 30) |
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if err != nil { |
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return nil, err |
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} |
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tag.Comment = util.ToString(comment) |
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tag.Track = 0 |
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var track int = 0 |
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// check if 29th byte is null byte (v1.0 or v1.1) |
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if comment[28] == 0 { |
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// it is v1.1, track number exists |
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track, err = util.ByteToInt(comment[29]) |
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if err != nil { |
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return nil, fmt.Errorf("could not get int from byte: %s", err) |
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} |
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tag.Track = uint8(track) |
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comment = comment[0:28] |
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tag.Comment = util.ToString(comment) |
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} |
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// Genre |
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genreByte, err := util.Read(rs, 1) |
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if err != nil { |
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return nil, err |
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} |
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genreInt, err := util.ByteToInt(genreByte[0]) |
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if err != nil { |
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return nil, fmt.Errorf("cannot convert bytes to int: %s", err) |
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} |
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genre, exists := id3v1genres[int(genreInt)] |
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if !exists { |
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genre = "" |
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} |
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tag.Genre = genre |
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if track == 0 { |
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tag.Version = V1_0 |
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} else { |
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tag.Version = V1_1 |
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} |
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return &tag, nil |
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}
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