126 lines
2.2 KiB
Go
126 lines
2.2 KiB
Go
package qmc
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import (
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"encoding/binary"
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"errors"
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"io"
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"strconv"
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"strings"
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)
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type Mflac0Decoder struct {
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r io.ReadSeeker
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audioLen int
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decodedKey []byte
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rc4 *rc4Cipher
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offset int
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rawMetaExtra1 int
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rawMetaExtra2 int
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}
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func (d *Mflac0Decoder) Read(p []byte) (int, error) {
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n := len(p)
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if d.audioLen-d.offset <= 0 {
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return 0, io.EOF
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} else if d.audioLen-d.offset < n {
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n = d.audioLen - d.offset
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}
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m, err := d.r.Read(p[:n])
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if m == 0 {
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return 0, err
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}
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d.rc4.Process(p[:m], d.offset)
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d.offset += m
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return m, err
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}
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func NewMflac0Decoder(r io.ReadSeeker) (*Mflac0Decoder, error) {
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d := &Mflac0Decoder{r: r}
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if err := d.searchKey(); err != nil {
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return nil, err
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}
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if len(d.decodedKey) > 300 {
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var err error
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d.rc4, err = NewRC4Cipher(d.decodedKey)
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if err != nil {
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return nil, err
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}
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} else {
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panic("not implement") //todo: impl
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}
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_, err := d.r.Seek(0, io.SeekStart)
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if err != nil {
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return nil, err
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}
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return d, nil
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}
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func (d *Mflac0Decoder) searchKey() error {
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if _, err := d.r.Seek(-4, 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.r, 4))
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if err != nil {
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return err
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}
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if string(buf) == "QTag" {
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if err := d.readRawMetaQTag(); err != nil {
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return err
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}
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} // todo: ...
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return nil
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}
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func (d *Mflac0Decoder) readRawMetaQTag() error {
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// get raw meta data len
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if _, err := d.r.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.r, 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.r.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.r, 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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{
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d.decodedKey, err = DecryptKey([]byte(items[0]))
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if err != nil {
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return err
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}
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}
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d.rawMetaExtra1, 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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