refactor: rework on MusicEx footer parser

This commit is contained in:
Jixun 2024-07-06 20:32:26 +01:00
parent 849f6730b6
commit 93839580c0
3 changed files with 77 additions and 49 deletions

View File

@ -98,6 +98,7 @@ func OpenMMKV(mmkvPath string, key string, logger *zap.Logger) error {
return nil return nil
} }
// /
func readKeyFromMMKVCustom(mid string) ([]byte, error) { func readKeyFromMMKVCustom(mid string) ([]byte, error) {
if streamKeyVault == nil { if streamKeyVault == nil {
return nil, fmt.Errorf("mmkv vault not loaded") return nil, fmt.Errorf("mmkv vault not loaded")

View File

@ -145,13 +145,12 @@ func (d *Decoder) searchKey() (err error) {
case "STag": case "STag":
return errors.New("qmc: file with 'STag' suffix doesn't contains media key") return errors.New("qmc: file with 'STag' suffix doesn't contains media key")
case "cex\x00": case "cex\x00":
footer := qqMusicTagMusicEx{} footer, err := NewMusicExTag(d.raw)
audioLen, err := footer.Read(d.raw)
if err != nil { if err != nil {
return err return err
} }
d.audioLen = int(audioLen) d.audioLen = fileSize - int(footer.TagSize)
d.decodedKey, err = readKeyFromMMKVCustom(footer.mediafile) d.decodedKey, err = readKeyFromMMKVCustom(footer.MediaFileName)
if err != nil { if err != nil {
return err return err
} }

View File

@ -1,65 +1,93 @@
package qmc package qmc
import ( import (
bytes "bytes"
"encoding/binary" "encoding/binary"
"errors"
"fmt" "fmt"
"io" "io"
"strings"
) )
type qqMusicTagMusicEx struct { type MusicExTagV1 struct {
songid uint32 // Song ID SongID uint32 // Song ID
unknown_1 uint32 // unused & unknown Unknown1 uint32 // unused & unknown
unknown_2 uint32 // unused & unknown Unknown2 uint32 // unused & unknown
mid string // Media ID MediaID string // Media ID
mediafile string // real file name MediaFileName string // real file name
unknown_3 uint32 // unused; uninitialized memory? Unknown3 uint32 // unused; uninitialized memory?
sizeof_struct uint32 // 19.57: fixed value: 0xC0
version uint32 // 19.57: fixed value: 0x01 // 16 byte at the end of tag.
tag_magic []byte // fixed value "musicex\0" (8 bytes) // TagSize should be respected when parsing.
TagSize uint32 // 19.57: fixed value: 0xC0
TagVersion uint32 // 19.57: fixed value: 0x01
TagMagic []byte // fixed value "musicex\0" (8 bytes)
} }
func (tag *qqMusicTagMusicEx) Read(raw io.ReadSeeker) (int64, error) { func NewMusicExTag(f io.ReadSeeker) (*MusicExTagV1, error) {
_, err := raw.Seek(-16, io.SeekEnd) _, err := f.Seek(-16, io.SeekEnd)
if err != nil { if err != nil {
return 0, fmt.Errorf("musicex seek error: %w", err) return nil, fmt.Errorf("musicex seek error: %w", err)
} }
footerBuf := make([]byte, 4) buffer := make([]byte, 16)
footerBuf, err = io.ReadAll(io.LimitReader(raw, 4)) bytesRead, err := f.Read(buffer)
if err != nil { if err != nil {
return 0, fmt.Errorf("get musicex error: %w", err) return nil, fmt.Errorf("get musicex error: %w", err)
}
if bytesRead != 16 {
return nil, fmt.Errorf("MusicExV1: read %d bytes (expected %d)", bytesRead, 16)
} }
footerLen := int64(binary.LittleEndian.Uint32(footerBuf))
audioLen, err := raw.Seek(-footerLen, io.SeekEnd) tag := &MusicExTagV1{
buf, err := io.ReadAll(io.LimitReader(raw, audioLen)) TagSize: binary.LittleEndian.Uint32(buffer[0x00:0x04]),
TagVersion: binary.LittleEndian.Uint32(buffer[0x04:0x08]),
TagMagic: buffer[0x04:0x0C],
}
if !bytes.Equal(tag.TagMagic, []byte("musicex\x00")) {
return nil, errors.New("MusicEx magic mismatch")
}
if tag.TagVersion != 1 {
return nil, errors.New(fmt.Sprintf("unsupported musicex tag version. expecting 1, got %d", tag.TagVersion))
}
if tag.TagSize < 0xC0 {
return nil, errors.New(fmt.Sprintf("unsupported musicex tag size. expecting at least 0xC0, got 0x%02x", tag.TagSize))
}
buffer = make([]byte, tag.TagSize)
bytesRead, err = f.Read(buffer)
if err != nil { if err != nil {
return 0, err return nil, err
}
if uint32(bytesRead) != tag.TagSize {
return nil, fmt.Errorf("MusicExV1: read %d bytes (expected %d)", bytesRead, tag.TagSize)
} }
tag.songid = binary.LittleEndian.Uint32(buf[0:4]) tag.SongID = binary.LittleEndian.Uint32(buffer[0x00:0x04])
tag.unknown_1 = binary.LittleEndian.Uint32(buf[4:8]) tag.Unknown1 = binary.LittleEndian.Uint32(buffer[0x04:0x08])
tag.unknown_2 = binary.LittleEndian.Uint32(buf[8:12]) tag.Unknown2 = binary.LittleEndian.Uint32(buffer[0x08:0x0C])
tag.MediaID = readUnicodeTagName(buffer[0x0C:], 30*2)
for i := 0; i < 30; i++ { tag.MediaFileName = readUnicodeTagName(buffer[0x48:], 50*2)
u := binary.LittleEndian.Uint16(buf[12+i*2 : 12+(i+1)*2]) tag.Unknown3 = binary.LittleEndian.Uint32(buffer[0xAC:0xB0])
if u == 0 { return tag, nil
break }
}
tag.mid += string(u) // readUnicodeTagName reads a buffer to maxLen.
} // reconstruct text by skipping alternate char (ascii chars encoded in UTF-16-LE),
for i := 0; i < 50; i++ { // until finding a zero or reaching maxLen.
u := binary.LittleEndian.Uint16(buf[72+i*2 : 72+(i+1)*2]) func readUnicodeTagName(buffer []byte, maxLen int) string {
if u == 0 { builder := strings.Builder{}
break
} for i := 0; i < maxLen; i += 2 {
tag.mediafile += string(u) chr := buffer[i]
} if chr != 0 {
builder.WriteByte(chr)
tag.unknown_3 = binary.LittleEndian.Uint32(buf[173:177]) } else {
tag.sizeof_struct = binary.LittleEndian.Uint32(buf[177:181]) break
tag.version = binary.LittleEndian.Uint32(buf[181:185]) }
tag.tag_magic = buf[185:193] }
return audioLen, nil return builder.String()
} }