Files
mautrix-telegram/pkg/gotd/fileid/decode.go
T
2025-06-27 20:03:37 -07:00

46 lines
1.1 KiB
Go

package fileid
import (
"encoding/base64"
"github.com/go-faster/errors"
"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
)
const (
persistentIDVersionOld = 2
persistentIDVersionMap = 3
persistentIDVersion = 4
)
// DecodeFileID parses FileID from a string.
func DecodeFileID(s string) (fileID FileID, _ error) {
if s == "" {
return FileID{}, errors.New("input is empty")
}
data, err := base64Decode(s)
if err != nil {
return FileID{}, errors.Wrap(err, "base64")
}
data = rleDecode(data)
if len(data) < 2 {
return FileID{}, errors.New("RLE-decoded data is too small")
}
switch version := data[len(data)-1]; version {
case persistentIDVersionOld, persistentIDVersionMap:
return FileID{}, errors.Errorf("%v is unsupported now", version)
case persistentIDVersion:
data = data[:len(data)-1]
err := fileID.decodeLatestFileID(&bin.Buffer{Buf: data})
return fileID, err
default:
return FileID{}, errors.Errorf("unknown file_id version %x", version)
}
}
func base64Decode(s string) ([]byte, error) {
return base64.RawURLEncoding.DecodeString(s)
}