83 lines
1.3 KiB
Go
83 lines
1.3 KiB
Go
package tag
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import (
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"fmt"
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"io"
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"os"
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)
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// Identify identifies the format and file type of the data in the ReadSeeker.
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func Identify(r io.ReadSeeker) (format Format, fileType FileType, err error) {
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b, err := readBytes(r, 11)
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if err != nil {
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return
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}
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_, err = r.Seek(-11, os.SEEK_CUR)
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if err != nil {
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err = fmt.Errorf("could not seek back to original position: %v", err)
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return
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}
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switch {
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case string(b[0:4]) == "fLaC":
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return VORBIS, FLAC, nil
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case string(b[0:4]) == "OggS":
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return VORBIS, OGG, nil
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case string(b[4:8]) == "ftyp":
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b = b[8:11]
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fileType = UnknownFileType
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switch string(b) {
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case "M4A":
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fileType = M4A
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case "M4B":
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fileType = M4B
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case "M4P":
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fileType = M4P
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}
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return MP4, fileType, nil
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case string(b[0:3]) == "ID3":
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b := b[3:]
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switch uint(b[0]) {
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case 2:
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format = ID3v2_2
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case 3:
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format = ID3v2_3
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case 4:
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format = ID3v2_4
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case 0, 1:
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fallthrough
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default:
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err = fmt.Errorf("ID3 version: %v, expected: 2, 3 or 4", uint(b[0]))
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return
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}
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return format, MP3, nil
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}
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n, err := r.Seek(-128, os.SEEK_END)
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if err != nil {
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return
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}
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tag, err := readString(r, 3)
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if err != nil {
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return
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}
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_, err = r.Seek(-n, os.SEEK_CUR)
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if err != nil {
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return
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}
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if tag != "TAG" {
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err = ErrNoTagsFound
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return
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}
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return ID3v1, MP3, nil
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}
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