majomi/tag
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Add Identity function for identifying metadata/filetypes.

Browse Source
This commit is contained in:
David Howden 2015-07-02 23:07:17 +10:00
parent 92e6d71ddb
commit b60e529091
2 changed files with 83 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

70
id.go Normal file
View File

@ -0,0 +1,70 @@
package tag
import (
"fmt"
"io"
"os"
)
// Identify reads from the given ReadSeaker and
func Identify(r io.ReadSeeker) (format Format, fileType FileType, err error) {
b, err := readBytes(r, 11)
if err != nil {
return
}
_, err = r.Seek(-11, os.SEEK_CUR)
if err != nil {
err = fmt.Errorf("could not seek back to original position: %v", err)
return
}
switch {
case string(b[0:4]) == "fLaC":
return VORBIS, FLAC, nil
case string(b[0:4]) == "OggS":
return VORBIS, OGG, nil
case string(b[4:11]) == "ftypM4A":
return AAC, MP4, nil
case string(b[0:3]) == "ID3":
b := b[3:]
switch uint(b[0]) {
case 2:
format = ID3v2_2
case 3:
format = ID3v2_3
case 4:
format = ID3v2_4
case 0, 1:
fallthrough
default:
err = fmt.Errorf("ID3 version: %v, expected: 2, 3 or 4", uint(b[0]))
return
}
return format, MP3, nil
}
n, err := r.Seek(-128, os.SEEK_END)
if err != nil {
return
}
tag, err := readString(r, 3)
if err != nil {
return
}
_, err = r.Seek(-n, os.SEEK_CUR)
if err != nil {
return
}
if tag != "TAG" {
err = ErrNoTagsFound
return
}
return ID3v1, MP3, nil
}

24
tag.go
View File

@ -68,12 +68,13 @@ type Format string
// Supported tag formats.
const (
ID3v1 Format = "ID3v1" // ID3v1 tag format.
ID3v2_2 = "ID3v2.2" // ID3v2.2 tag format.
ID3v2_3 = "ID3v2.3" // ID3v2.3 tag format (most common).
ID3v2_4 = "ID3v2.4" // ID3v2.4 tag format.
MP4 = "MP4" // MP4 tag (atom) format.
VORBIS = "VORBIS" // Vorbis Comment tag format.
UnknownFormat Format = "" // Unknown Format.
ID3v1 = "ID3v1" // ID3v1 tag format.
ID3v2_2 = "ID3v2.2" // ID3v2.2 tag format.
ID3v2_3 = "ID3v2.3" // ID3v2.3 tag format (most common).
ID3v2_4 = "ID3v2.4" // ID3v2.4 tag format.
MP4 = "MP4" // MP4 tag (atom) format.
VORBIS = "VORBIS" // Vorbis Comment tag format.
)
// FileType is an enumeration of the audio file types supported by this package, in particular
@ -83,11 +84,12 @@ type FileType string
// Supported file types.
const (
MP3 FileType = "MP3" // MP3 file
AAC = "AAC" // M4A file (MP4)
ALAC = "ALAC" // Apple Lossless file FIXME: actually detect this
FLAC = "FLAC" // FLAC file
OGG = "OGG" // OGG file
UnknownFileType FileType = "" // Unknown FileType.
MP3 = "MP3" // MP3 file
AAC = "AAC" // M4A file (MP4)
ALAC = "ALAC" // Apple Lossless file FIXME: actually detect this
FLAC = "FLAC" // FLAC file
OGG = "OGG" // OGG file
)
// Metadata is an interface which is used to describe metadata retrieved by this package.