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forked from um/cli
cli/algo/kgm/kgm.go

92 lines
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2020-12-25 18:54:07 +00:00
package kgm
import (
"bytes"
"encoding/binary"
"errors"
"github.com/umlock-music/cli/algo/common"
"github.com/umlock-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) *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 ""
}
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] //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("文件过大,处理后的音频不完整,请向我们报告此文件的信息")
lenData = fullMaskLen
}
d.audio = make([]byte, lenData)
for i := 0; i < lenData; i++ {
med8 := d.key[i%17] ^ dataEncrypted[i]
med8 ^= (med8 & 0xf) << 4
msk8 := maskV2PreDef[i%272] ^ maskV2[i>>4]
msk8 ^= (msk8 & 0xf) << 4
d.audio[i] = med8 ^ msk8
}
if d.isVpr {
for i := 0; i < lenData; i++ {
d.audio[i] ^= maskDiffVpr[i%17]
}
}
return nil
}