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unlock-music-cli/algo/qmc/qmc.go

97 lines
2.0 KiB
Go

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package qmc
import (
"encoding/base64"
"encoding/binary"
"errors"
"github.com/umlock-music/cli/algo/common"
)
var (
ErrQmcFileLength = errors.New("invalid qmc file length")
ErrQmcKeyDecodeFailed = errors.New("base64 decode qmc key failed")
ErrQmcKeyLength = errors.New("unexpected decoded qmc key length")
)
type Decoder struct {
file []byte
maskDetector func(encodedData []byte) (*Key256Mask, error)
mask *Key256Mask
audioExt string
key []byte
audio []byte
}
func NewDefaultDecoder(data []byte) *Decoder {
return &Decoder{file: data, mask: getDefaultMask()}
}
func NewMflac256Decoder(data []byte) *Decoder {
return &Decoder{file: data, maskDetector: detectMflac256Mask, audioExt: "flac"}
}
func NewMgg256Decoder(data []byte) *Decoder {
return &Decoder{file: data, maskDetector: detectMgg256Mask, audioExt: "ogg"}
}
func (d *Decoder) Validate() error {
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if nil != d.mask {
return nil
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}
if nil != d.maskDetector {
if err := d.validateKey(); err != nil {
return err
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}
var err error
d.mask, err = d.maskDetector(d.file)
return err
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}
return errors.New("no mask or mask detector found")
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}
func (d *Decoder) validateKey() error {
lenData := len(d.file)
if lenData < 4 {
return ErrQmcFileLength
}
keyLen := binary.LittleEndian.Uint32(d.file[lenData-4:])
if lenData < int(keyLen+4) {
return ErrQmcFileLength
}
var err error
d.key, err = base64.StdEncoding.DecodeString(
string(d.file[lenData-4-int(keyLen) : lenData-4]))
if err != nil {
return ErrQmcKeyDecodeFailed
}
if len(d.key) != 272 {
return ErrQmcKeyLength
}
d.file = d.file[:lenData-4-int(keyLen)]
return nil
}
func (d *Decoder) Decode() error {
d.audio = d.mask.Decrypt(d.file)
return nil
}
func (d Decoder) GetCoverImage() []byte {
return nil
}
func (d Decoder) GetAudioData() []byte {
return d.audio
}
func (d Decoder) GetAudioExt() string {
return d.audioExt
}
func (d Decoder) GetMeta() common.Meta {
return nil
}