101 lines
2.2 KiB
Go
101 lines
2.2 KiB
Go
package kwm
|
|
|
|
import (
|
|
"bytes"
|
|
"errors"
|
|
"fmt"
|
|
"io"
|
|
"strconv"
|
|
"strings"
|
|
"unicode"
|
|
|
|
"unlock-music.dev/cli/algo/common"
|
|
)
|
|
|
|
const magicHeader1 = "yeelion-kuwo-tme"
|
|
const magicHeader2 = "yeelion-kuwo\x00\x00\x00\x00"
|
|
const keyPreDefined = "MoOtOiTvINGwd2E6n0E1i7L5t2IoOoNk"
|
|
|
|
type Decoder struct {
|
|
rd io.ReadSeeker
|
|
|
|
cipher common.StreamDecoder
|
|
offset int
|
|
|
|
outputExt string
|
|
bitrate int
|
|
}
|
|
|
|
func (d *Decoder) GetAudioExt() string {
|
|
return "." + d.outputExt
|
|
}
|
|
|
|
func NewDecoder(rd io.ReadSeeker) common.Decoder {
|
|
return &Decoder{rd: rd}
|
|
}
|
|
|
|
// Validate checks if the file is a valid Kuwo .kw file.
|
|
// rd will be seeked to the beginning of the encrypted audio.
|
|
func (d *Decoder) Validate() error {
|
|
header := make([]byte, 0x400) // kwm header is fixed to 1024 bytes
|
|
_, err := io.ReadFull(d.rd, header)
|
|
if err != nil {
|
|
return fmt.Errorf("kwm read header: %w", err)
|
|
}
|
|
|
|
// check magic header, 0x00 - 0x0F
|
|
magicHeader := header[:0x10]
|
|
if !bytes.Equal([]byte(magicHeader1), magicHeader) &&
|
|
!bytes.Equal([]byte(magicHeader2), magicHeader) {
|
|
return errors.New("kwm magic header not matched")
|
|
}
|
|
|
|
d.cipher = newKwmCipher(header[0x18:0x20]) // Crypto Key, 0x18 - 0x1F
|
|
d.bitrate, d.outputExt = parseBitrateAndType(header[0x30:0x38]) // Bitrate & File Extension, 0x30 - 0x38
|
|
|
|
return nil
|
|
}
|
|
|
|
func parseBitrateAndType(header []byte) (int, string) {
|
|
tmp := strings.TrimRight(string(header), "\x00")
|
|
sep := strings.IndexFunc(tmp, func(r rune) bool {
|
|
return !unicode.IsDigit(r)
|
|
})
|
|
|
|
bitrate, _ := strconv.Atoi(tmp[:sep]) // just ignore the error
|
|
outputExt := strings.ToLower(tmp[sep:])
|
|
return bitrate, outputExt
|
|
}
|
|
|
|
func (d *Decoder) Read(b []byte) (int, error) {
|
|
n, err := d.rd.Read(b)
|
|
if n > 0 {
|
|
d.cipher.Decrypt(b[:n], d.offset)
|
|
d.offset += n
|
|
}
|
|
return n, err
|
|
}
|
|
|
|
func padOrTruncate(raw string, length int) string {
|
|
lenRaw := len(raw)
|
|
out := raw
|
|
if lenRaw == 0 {
|
|
out = string(make([]byte, length))
|
|
} else if lenRaw > length {
|
|
out = raw[:length]
|
|
} else if lenRaw < length {
|
|
_tmp := make([]byte, 32)
|
|
for i := 0; i < 32; i++ {
|
|
_tmp[i] = raw[i%lenRaw]
|
|
}
|
|
out = string(_tmp)
|
|
}
|
|
return out
|
|
}
|
|
|
|
func init() {
|
|
// Kuwo Mp3/Flac
|
|
common.RegisterDecoder("kwm", false, NewDecoder)
|
|
common.RegisterDecoder("kwm", false, common.NewRawDecoder)
|
|
}
|