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99 lines
2.1 KiB
Go
99 lines
2.1 KiB
Go
package xm
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import (
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"bytes"
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"errors"
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"github.com/unlock-music/cli/algo/common"
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)
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var (
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magicHeader = []byte{'i', 'f', 'm', 't'}
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magicHeader2 = []byte{0xfe, 0xfe, 0xfe, 0xfe}
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typeMapping = map[string]string{
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" WAV": "wav",
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"FLAC": "flac",
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" MP3": "mp3",
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" A4M": "m4a",
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}
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ErrFileSize = errors.New("xm invalid file size")
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ErrMagicHeader = errors.New("xm magic header not matched")
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)
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type Decoder struct {
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file []byte
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headerLen uint32
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outputExt string
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mask byte
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audio []byte
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}
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func (d *Decoder) GetAudioData() []byte {
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return d.audio
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}
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func (d *Decoder) GetAudioExt() string {
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if d.outputExt != "" {
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return "." + d.outputExt
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}
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return ""
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}
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func (d *Decoder) GetMeta() common.Meta {
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return nil
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}
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func NewDecoder(data []byte) common.Decoder {
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return &Decoder{file: data}
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}
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func (d *Decoder) Validate() error {
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lenData := len(d.file)
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if lenData < 16 {
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return ErrFileSize
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}
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if !bytes.Equal(magicHeader, d.file[:4]) ||
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!bytes.Equal(magicHeader2, d.file[8:12]) {
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return ErrMagicHeader
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}
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var ok bool
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d.outputExt, ok = typeMapping[string(d.file[4:8])]
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if !ok {
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return errors.New("detect unknown xm file type: " + string(d.file[4:8]))
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}
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d.headerLen = uint32(d.file[12]) | uint32(d.file[13])<<8 | uint32(d.file[14])<<16 // LittleEndian Unit24
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if d.headerLen+16 > uint32(lenData) {
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return ErrFileSize
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}
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return nil
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}
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func (d *Decoder) Decode() error {
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d.mask = d.file[15]
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d.audio = d.file[16:]
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dataLen := uint32(len(d.audio))
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for i := d.headerLen; i < dataLen; i++ {
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d.audio[i] = ^(d.audio[i] - d.mask)
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}
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return nil
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}
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func DecoderFuncWithExt(ext string) common.NewDecoderFunc {
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return func(file []byte) common.Decoder {
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return &Decoder{file: file, outputExt: ext}
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}
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}
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func init() {
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// Xiami Wav/M4a/Mp3/Flac
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common.RegisterDecoder("xm", false, NewDecoder)
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// Xiami Typed Format
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common.RegisterDecoder("wav", false, DecoderFuncWithExt("wav"))
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common.RegisterDecoder("mp3", false, DecoderFuncWithExt("mp3"))
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common.RegisterDecoder("flac", false, DecoderFuncWithExt("flac"))
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common.RegisterDecoder("m4a", false, DecoderFuncWithExt("m4a"))
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}
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