83 lines
1.6 KiB
Go
83 lines
1.6 KiB
Go
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/unlock-music/cli/algo/common"
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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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maskFunc func(int) byte
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audio []byte
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}
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func NewDecoder(file []byte) common.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 "" // use sniffer
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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.maskFunc = getKgmMask
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} else if bytes.Equal(vprHeader, d.file[:len(vprHeader)]) {
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d.maskFunc = getVprMask
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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] //todo: 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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d.audio = d.file[headerLen:]
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for i := 0; i < len(d.audio); i++ {
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med8 := d.audio[i] ^ d.key[i%17] ^ d.maskFunc(i)
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d.audio[i] = med8 ^ (med8&0xf)<<4
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}
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return nil
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}
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func init() {
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// Kugou
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common.RegisterDecoder("kgm", false, NewDecoder)
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common.RegisterDecoder("kgma", false, NewDecoder)
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// Viper
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common.RegisterDecoder("vpr", false, NewDecoder)
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}
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