refactor: code cleaning

algo/kgm/kgm.go

@@ -8,17 +8,20 @@ import (
 )
 
 type Decoder struct {
-	header header
-	cipher common.StreamDecoder
+	rd io.ReadSeeker
 
-	rd     io.ReadSeeker
+	cipher common.StreamDecoder
 	offset int
+
+	header header
 }
 
 func NewDecoder(rd io.ReadSeeker) common.Decoder {
 	return &Decoder{rd: rd}
 }
 
+// Validate checks if the file is a valid Kugou (.kgm, .vpr, .kgma) file.
+// rd will be seeked to the beginning of the encrypted audio.
 func (d *Decoder) Validate() (err error) {
 	if err := d.header.FromFile(d.rd); err != nil {
 		return err

algo/kwm/kwm.go

@@ -16,9 +16,9 @@ const magicHeader = "yeelion-kuwo-tme"
 const keyPreDefined = "MoOtOiTvINGwd2E6n0E1i7L5t2IoOoNk"
 
 type Decoder struct {
-	cipher common.StreamDecoder
+	rd io.ReadSeeker
 
-	rd     io.ReadSeeker
+	cipher common.StreamDecoder
 	offset int
 
 	outputExt string
@@ -33,6 +33,8 @@ 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)

algo/ncm/ncm.go

@@ -36,22 +36,19 @@ func NewDecoder(rd io.ReadSeeker) common.Decoder {
 }
 
 type Decoder struct {
-	rd     io.ReadSeeker
+	rd io.ReadSeeker // rd is the original file reader
+
 	offset int
-
 	cipher common.StreamDecoder
 
-	key []byte
-	box []byte
-
 	metaRaw  []byte
 	metaType string
 	meta     RawMeta
-
-	cover []byte
-	audio []byte
+	cover    []byte
 }
 
+// Validate checks if the file is a valid Netease .ncm file.
+// rd will be seeked to the beginning of the encrypted audio.
 func (d *Decoder) Validate() error {
 	if err := d.validateMagicHeader(); err != nil {
 		return err

algo/qmc/qmc.go

@@ -13,14 +13,15 @@ import (
 )
 
 type Decoder struct {
-	raw      io.ReadSeeker
-	audio    io.Reader
-	offset   int
-	audioLen int
+	raw io.ReadSeeker // raw is the original file reader
 
-	cipher common.StreamDecoder
+	audio    io.Reader // audio is the encrypted audio data
+	audioLen int       // audioLen is the audio data length
+	offset   int       // offset is the current audio read position
+
+	decodedKey []byte // decodedKey is the decoded key for cipher
+	cipher     common.StreamDecoder
 
-	decodedKey    []byte
 	rawMetaExtra1 int
 	rawMetaExtra2 int
 }
@@ -100,23 +101,29 @@ func (d *Decoder) searchKey() error {
 	if err != nil {
 		return err
 	}
-	buf, err := io.ReadAll(io.LimitReader(d.raw, 4))
-	if err != nil {
+
+	suffixBuf := make([]byte, 4)
+	if _, err := io.ReadFull(d.raw, suffixBuf); err != nil {
 		return err
 	}
-	if string(buf) == "QTag" {
+
+	switch string(suffixBuf) {
+	case "QTag":
 		return d.readRawMetaQTag()
-	} else if string(buf) == "STag" {
+	case "STag":
 		return errors.New("qmc: file with 'STag' suffix doesn't contains media key")
-	} else {
-		size := binary.LittleEndian.Uint32(buf)
+	default:
+		size := binary.LittleEndian.Uint32(suffixBuf)
+
 		if size <= 0xFFFF && size != 0 { // assume size is key len
 			return d.readRawKey(int64(size))
 		}
+
 		// try to use default static cipher
 		d.audioLen = int(fileSizeM4 + 4)
 		return nil
 	}
+
 }
 
 func (d *Decoder) readRawKey(rawKeyLen int64) error {

algo/tm/tm.go

@@ -13,9 +13,10 @@ var replaceHeader = []byte{0x00, 0x00, 0x00, 0x20, 0x66, 0x74, 0x79, 0x70}
 var magicHeader = []byte{0x51, 0x51, 0x4D, 0x55} //0x15, 0x1D, 0x1A, 0x21
 
 type Decoder struct {
-	raw    io.ReadSeeker
+	raw io.ReadSeeker // raw is the original file reader
+
 	offset int
-	audio  io.Reader
+	audio  io.Reader // audio is the decrypted audio data
 }
 
 func (d *Decoder) Validate() error {

algo/xiami/xm.go

@@ -22,13 +22,11 @@ var (
 )
 
 type Decoder struct {
-	rd     io.ReadSeeker
+	rd     io.ReadSeeker // rd is the original file reader
 	offset int
 
 	cipher    common.StreamDecoder
 	outputExt string
-	mask      byte
-	audio     []byte
 }
 
 func (d *Decoder) GetAudioExt() string {
@@ -43,6 +41,8 @@ func NewDecoder(rd io.ReadSeeker) common.Decoder {
 	return &Decoder{rd: rd}
 }
 
+// Validate checks if the file is a valid xiami .xm file.
+// rd will set to the beginning of the encrypted audio data.
 func (d *Decoder) Validate() error {
 	header := make([]byte, 16) // xm header is fixed to 16 bytes
 

internal/logging/zap.go

@@ -7,6 +7,7 @@ import (
 
 func NewZapLogger() (*zap.Logger, error) {
 	zapCfg := zap.NewDevelopmentConfig()
+	zapCfg.DisableStacktrace = true
 	zapCfg.EncoderConfig.EncodeLevel = zapcore.CapitalColorLevelEncoder
 	zapCfg.EncoderConfig.EncodeTime = zapcore.TimeEncoderOfLayout("2006/01/02 15:04:05.000")
 	return zapCfg.Build()