cli/algo/kgm/kgm.go
2021-11-11 23:43:20 +08:00

95 lines
2.0 KiB
Go

package kgm
import (
"bytes"
"encoding/binary"
"errors"
"github.com/unlock-music/cli/algo/common"
"github.com/unlock-music/cli/internal/logging"
)
var (
vprHeader = []byte{
0x05, 0x28, 0xBC, 0x96, 0xE9, 0xE4, 0x5A, 0x43,
0x91, 0xAA, 0xBD, 0xD0, 0x7A, 0xF5, 0x36, 0x31}
kgmHeader = []byte{
0x7C, 0xD5, 0x32, 0xEB, 0x86, 0x02, 0x7F, 0x4B,
0xA8, 0xAF, 0xA6, 0x8E, 0x0F, 0xFF, 0x99, 0x14}
ErrKgmMagicHeader = errors.New("kgm/vpr magic header not matched")
)
type Decoder struct {
file []byte
key []byte
isVpr bool
audio []byte
}
func NewDecoder(file []byte) common.Decoder {
return &Decoder{
file: file,
}
}
func (d Decoder) GetCoverImage() []byte {
return nil
}
func (d Decoder) GetAudioData() []byte {
return d.audio
}
func (d Decoder) GetAudioExt() string {
return "" // use sniffer
}
func (d Decoder) GetMeta() common.Meta {
return nil
}
func (d *Decoder) Validate() error {
if bytes.Equal(kgmHeader, d.file[:len(kgmHeader)]) {
d.isVpr = false
} else if bytes.Equal(vprHeader, d.file[:len(vprHeader)]) {
d.isVpr = true
} else {
return ErrKgmMagicHeader
}
d.key = d.file[0x1c:0x2c]
d.key = append(d.key, 0x00)
_ = d.file[0x2c:0x3c] //todo: key2
return nil
}
func (d *Decoder) Decode() error {
headerLen := binary.LittleEndian.Uint32(d.file[0x10:0x14])
dataEncrypted := d.file[headerLen:]
lenData := len(dataEncrypted)
initMask()
if fullMaskLen < lenData {
logging.Log().Warn("The file is too large and the processed audio is incomplete, " +
"please report to us about this file at https://github.com/unlock-music/cli/issues")
lenData = fullMaskLen
}
d.audio = make([]byte, lenData)
for i := 0; i < lenData; i++ {
med8 := dataEncrypted[i] ^ d.key[i%17] ^ maskV2PreDef[i%(16*17)] ^ maskV2[i>>4]
d.audio[i] = med8 ^ (med8&0xf)<<4
}
if d.isVpr {
for i := 0; i < lenData; i++ {
d.audio[i] ^= maskDiffVpr[i%17]
}
}
return nil
}
func init() {
// Kugou
common.RegisterDecoder("kgm", false, NewDecoder)
common.RegisterDecoder("kgma", false, NewDecoder)
// Viper
common.RegisterDecoder("vpr", false, NewDecoder)
}