277 lines
6.4 KiB
Go
277 lines
6.4 KiB
Go
package qmc
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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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"fmt"
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"io"
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"runtime"
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"strconv"
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"strings"
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"go.uber.org/zap"
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"unlock-music.dev/cli/algo/common"
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"unlock-music.dev/cli/internal/sniff"
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)
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type Decoder struct {
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raw io.ReadSeeker // raw is the original file reader
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params *common.DecoderParams
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audio io.Reader // audio is the encrypted audio data
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audioLen int // audioLen is the audio data length
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offset int // offset is the current audio read position
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decodedKey []byte // decodedKey is the decoded key for cipher
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cipher common.StreamDecoder
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songID int
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rawMetaExtra2 int
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albumID int
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albumMediaID string
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// cache
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meta common.AudioMeta
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cover []byte
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embeddedCover bool // embeddedCover is true if the cover is embedded in the file
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probeBuf *bytes.Buffer // probeBuf is the buffer for sniffing metadata, TODO: consider pipe?
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// provider
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logger *zap.Logger
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}
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// Read implements io.Reader, offer the decrypted audio data.
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// Validate should call before Read to check if the file is valid.
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func (d *Decoder) Read(p []byte) (int, error) {
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n, err := d.audio.Read(p)
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if n > 0 {
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d.cipher.Decrypt(p[:n], d.offset)
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d.offset += n
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_, _ = d.probeBuf.Write(p[:n]) // bytes.Buffer.Write never return error
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}
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return n, err
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}
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func NewDecoder(p *common.DecoderParams) common.Decoder {
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return &Decoder{raw: p.Reader, params: p, logger: p.Logger}
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}
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func (d *Decoder) Validate() error {
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// search & derive key
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err := d.searchKey()
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if err != nil {
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return err
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}
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// check cipher type and init decode cipher
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if len(d.decodedKey) > 300 {
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d.cipher, err = newRC4Cipher(d.decodedKey)
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if err != nil {
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return err
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}
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} else if len(d.decodedKey) != 0 {
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d.cipher, err = newMapCipher(d.decodedKey)
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if err != nil {
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return err
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}
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} else {
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d.cipher = newStaticCipher()
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}
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// test with first 16 bytes
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if err := d.validateDecode(); err != nil {
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return err
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}
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// reset position, limit to audio, prepare for Read
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if _, err := d.raw.Seek(0, io.SeekStart); err != nil {
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return err
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}
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d.audio = io.LimitReader(d.raw, int64(d.audioLen))
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// prepare for sniffing metadata
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d.probeBuf = bytes.NewBuffer(make([]byte, 0, d.audioLen))
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return nil
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}
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func (d *Decoder) validateDecode() error {
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_, err := d.raw.Seek(0, io.SeekStart)
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if err != nil {
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return fmt.Errorf("qmc seek to start: %w", err)
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}
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buf := make([]byte, 64)
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if _, err := io.ReadFull(d.raw, buf); err != nil {
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return fmt.Errorf("qmc read header: %w", err)
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}
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d.cipher.Decrypt(buf, 0)
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_, ok := sniff.AudioExtension(buf)
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if !ok {
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return errors.New("qmc: detect file type failed")
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}
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return nil
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}
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func (d *Decoder) searchKey() (err error) {
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fileSizeM4, err := d.raw.Seek(-4, io.SeekEnd)
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if err != nil {
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return err
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}
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fileSize := int(fileSizeM4) + 4
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//goland:noinspection GoBoolExpressions
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if runtime.GOOS == "darwin" && !strings.HasPrefix(d.params.Extension, ".qmc") {
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d.decodedKey, err = readKeyFromMMKV(d.params.FilePath, d.logger)
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if err == nil {
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d.audioLen = fileSize
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return
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}
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d.logger.Warn("read key from mmkv failed", zap.Error(err))
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}
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suffixBuf := make([]byte, 4)
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if _, err := io.ReadFull(d.raw, suffixBuf); err != nil {
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return err
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}
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switch string(bytes.ReplaceAll(suffixBuf, []byte{0x00}, []byte{})) {
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case "QTag":
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return d.readRawMetaQTag()
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case "STag":
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return errors.New("qmc: file with 'STag' suffix doesn't contains media key")
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case "cex":
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d.decodedKey, err = readKeyFromMMKVCustom(d)
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if err == nil {
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suffix := []byte{0x63, 0x65, 0x78, 0x00} // cex
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for i := 0; i <= 3; i++ {
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// 末尾的信息数据每192字节出现一次，故只要循环判断末尾不为musicex时即为歌曲数据
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musicexLen, err := d.raw.Seek(int64(-(192*i)-4), io.SeekEnd)
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if err != nil {
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return fmt.Errorf("get musicexLen error: %w", err)
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}
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buf, err := io.ReadAll(io.LimitReader(d.raw, 4))
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if err != nil {
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return fmt.Errorf("get musicex error: %w", err)
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}
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if !bytes.Equal(buf, suffix) {
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d.audioLen = int(musicexLen) + 4
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return nil
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}
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}
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}
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return err
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default:
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size := binary.LittleEndian.Uint32(suffixBuf)
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if size <= 0xFFFF && size != 0 { // assume size is key len
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return d.readRawKey(int64(size))
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}
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// try to use default static cipher
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d.audioLen = fileSize
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return nil
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}
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}
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func (d *Decoder) readRawKey(rawKeyLen int64) error {
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audioLen, err := d.raw.Seek(-(4 + rawKeyLen), io.SeekEnd)
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if err != nil {
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return err
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}
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d.audioLen = int(audioLen)
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rawKeyData, err := io.ReadAll(io.LimitReader(d.raw, rawKeyLen))
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if err != nil {
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return err
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}
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// clean suffix NULs
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rawKeyData = bytes.TrimRight(rawKeyData, "\x00")
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d.decodedKey, err = deriveKey(rawKeyData)
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if err != nil {
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return err
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}
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return nil
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}
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func (d *Decoder) readRawMetaQTag() error {
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// get raw meta data len
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if _, err := d.raw.Seek(-8, io.SeekEnd); err != nil {
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return err
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}
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buf, err := io.ReadAll(io.LimitReader(d.raw, 4))
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if err != nil {
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return err
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}
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rawMetaLen := int64(binary.BigEndian.Uint32(buf))
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// read raw meta data
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audioLen, err := d.raw.Seek(-(8 + rawMetaLen), io.SeekEnd)
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if err != nil {
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return err
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}
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d.audioLen = int(audioLen)
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rawMetaData, err := io.ReadAll(io.LimitReader(d.raw, rawMetaLen))
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if err != nil {
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return err
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}
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items := strings.Split(string(rawMetaData), ",")
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if len(items) != 3 {
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return errors.New("invalid raw meta data")
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}
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d.decodedKey, err = deriveKey([]byte(items[0]))
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if err != nil {
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return err
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}
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d.songID, err = strconv.Atoi(items[1])
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if err != nil {
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return err
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}
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d.rawMetaExtra2, err = strconv.Atoi(items[2])
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if err != nil {
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return err
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}
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return nil
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}
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//goland:noinspection SpellCheckingInspection
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func init() {
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supportedExts := []string{
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"qmc0", "qmc3", //QQ Music MP3
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"qmc2", "qmc4", "qmc6", "qmc8", //QQ Music M4A
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"qmcflac", //QQ Music FLAC
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"qmcogg", //QQ Music OGG
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"tkm", //QQ Music Accompaniment M4A
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"bkcmp3", "bkcm4a", "bkcflac", "bkcwav", "bkcape", "bkcogg", "bkcwma", //Moo Music
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"666c6163", //QQ Music Weiyun Flac
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"6d7033", //QQ Music Weiyun Mp3
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"6f6767", //QQ Music Weiyun Ogg
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"6d3461", //QQ Music Weiyun M4a
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"776176", //QQ Music Weiyun Wav
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"mgg", "mgg1", "mggl", //QQ Music New Ogg
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"mflac", "mflac0", "mflach", //QQ Music New Flac
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"mmp4", // QQ Music MP4 Container, tipically used for Dolby EAC3 stream
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}
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for _, ext := range supportedExts {
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common.RegisterDecoder(ext, false, NewDecoder)
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}
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}
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