92 lines
1.8 KiB
Go
92 lines
1.8 KiB
Go
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package kgm
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"github.com/umlock-music/cli/algo/common"
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"github.com/umlock-music/cli/internal/logging"
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)
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var (
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vprHeader = []byte{
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0x05, 0x28, 0xBC, 0x96, 0xE9, 0xE4, 0x5A, 0x43,
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0x91, 0xAA, 0xBD, 0xD0, 0x7A, 0xF5, 0x36, 0x31}
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kgmHeader = []byte{
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0x7C, 0xD5, 0x32, 0xEB, 0x86, 0x02, 0x7F, 0x4B,
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0xA8, 0xAF, 0xA6, 0x8E, 0x0F, 0xFF, 0x99, 0x14}
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ErrKgmMagicHeader = errors.New("kgm/vpr magic header not matched")
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)
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type Decoder struct {
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file []byte
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key []byte
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isVpr bool
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audio []byte
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}
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func NewDecoder(file []byte) *Decoder {
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return &Decoder{
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file: file,
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}
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}
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func (d Decoder) GetCoverImage() []byte {
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return nil
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}
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func (d Decoder) GetAudioData() []byte {
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return d.audio
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}
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func (d Decoder) GetAudioExt() string {
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return ""
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}
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func (d Decoder) GetMeta() common.Meta {
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return nil
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}
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func (d *Decoder) Validate() error {
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if bytes.Equal(kgmHeader, d.file[:len(kgmHeader)]) {
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d.isVpr = false
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} else if bytes.Equal(vprHeader, d.file[:len(vprHeader)]) {
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d.isVpr = true
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} else {
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return ErrKgmMagicHeader
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}
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d.key = d.file[0x1c:0x2c]
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d.key = append(d.key, 0x00)
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_ = d.file[0x2c:0x3c] //key2
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return nil
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}
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func (d *Decoder) Decode() error {
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headerLen := binary.LittleEndian.Uint32(d.file[0x10:0x14])
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dataEncrypted := d.file[headerLen:]
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lenData := len(dataEncrypted)
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initMask()
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if fullMaskLen < lenData {
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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")
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lenData = fullMaskLen
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}
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d.audio = make([]byte, lenData)
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for i := 0; i < lenData; i++ {
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med8 := d.key[i%17] ^ dataEncrypted[i]
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med8 ^= (med8 & 0xf) << 4
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msk8 := maskV2PreDef[i%272] ^ maskV2[i>>4]
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msk8 ^= (msk8 & 0xf) << 4
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d.audio[i] = med8 ^ msk8
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}
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if d.isVpr {
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for i := 0; i < lenData; i++ {
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d.audio[i] ^= maskDiffVpr[i%17]
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}
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}
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return nil
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}
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