68 lines
1.4 KiB
Go
68 lines
1.4 KiB
Go
package kgm
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import (
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"fmt"
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"io"
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"unlock-music.dev/cli/algo/common"
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)
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type Decoder struct {
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rd io.ReadSeeker
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cipher common.StreamDecoder
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offset int
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header header
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}
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func NewDecoder(p *common.DecoderParams) common.Decoder {
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return &Decoder{rd: p.Reader}
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}
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// Validate checks if the file is a valid Kugou (.kgm, .vpr, .kgma) file.
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// rd will be seeked to the beginning of the encrypted audio.
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func (d *Decoder) Validate() (err error) {
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if err := d.header.FromFile(d.rd); err != nil {
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return err
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}
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// TODO; validate crypto version
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switch d.header.CryptoVersion {
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case 3:
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d.cipher, err = newKgmCryptoV3(&d.header)
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if err != nil {
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return fmt.Errorf("kgm init crypto v3: %w", err)
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}
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default:
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return fmt.Errorf("kgm: unsupported crypto version %d", d.header.CryptoVersion)
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}
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// prepare for read
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if _, err := d.rd.Seek(int64(d.header.AudioOffset), io.SeekStart); err != nil {
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return fmt.Errorf("kgm seek to audio: %w", err)
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}
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return nil
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}
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func (d *Decoder) Read(buf []byte) (int, error) {
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n, err := d.rd.Read(buf)
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if n > 0 {
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d.cipher.Decrypt(buf[:n], d.offset)
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d.offset += n
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}
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return n, err
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}
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func init() {
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// Kugou
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common.RegisterDecoder("kgm", false, NewDecoder)
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common.RegisterDecoder("kgma", false, NewDecoder)
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// Viper
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common.RegisterDecoder("vpr", false, NewDecoder)
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// Kugou Android
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common.RegisterDecoder("kgm.flac", false, NewDecoder)
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common.RegisterDecoder("vpr.flac", false, NewDecoder)
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}
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