package kgm import ( "bytes" "encoding/binary" "errors" "github.com/unlock-music/cli/algo/common" ) 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 maskFunc func(int) byte 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.maskFunc = getKgmMask } else if bytes.Equal(vprHeader, d.file[:len(vprHeader)]) { d.maskFunc = getVprMask } 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]) d.audio = d.file[headerLen:] for i := 0; i < len(d.audio); i++ { med8 := d.audio[i] ^ d.key[i%17] ^ d.maskFunc(i) d.audio[i] = med8 ^ (med8&0xf)<<4 } return nil } func init() { // Kugou common.RegisterDecoder("kgm", false, NewDecoder) common.RegisterDecoder("kgma", false, NewDecoder) // Viper common.RegisterDecoder("vpr", false, NewDecoder) }