refactor: use io.Reader instead of custom method

algo/common/common.go

@@ -1,13 +1,13 @@
 package common
 
-import "context"
+import (
+	"context"
+	"io"
+)
 
 type Decoder interface {
 	Validate() error
-	Decode() error
+	io.Reader
-	GetAudioData() []byte
-	GetAudioExt() string
-	GetMeta() Meta
 }
 
 type CoverImageGetter interface {
@@ -19,3 +19,7 @@ type Meta interface {
 	GetTitle() string
 	GetAlbum() string
 }
+
+type StreamDecoder interface {
+	Decrypt(buf []byte, offset int)
+}

algo/common/dispatch.go

@@ -1,11 +1,12 @@
 package common
 
 import (
+	"io"
 	"path/filepath"
 	"strings"
 )
 
-type NewDecoderFunc func([]byte) Decoder
+type NewDecoderFunc func(rd io.ReadSeeker) Decoder
 
 type decoderItem struct {
 	noop    bool

algo/common/raw.go

@@ -2,21 +2,32 @@ package common
 
 import (
 	"errors"
+	"fmt"
+	"io"
 	"strings"
 )
 
 type RawDecoder struct {
-	file     []byte
+	rd io.ReadSeeker
+
 	audioExt string
 }
 
-func NewRawDecoder(file []byte) Decoder {
+func NewRawDecoder(rd io.ReadSeeker) Decoder {
-	return &RawDecoder{file: file}
+	return &RawDecoder{rd: rd}
 }
 
 func (d *RawDecoder) Validate() error {
+	header := make([]byte, 16)
+	if _, err := io.ReadFull(d.rd, header); err != nil {
+		return fmt.Errorf("read file header failed: %v", err)
+	}
+	if _, err := d.rd.Seek(0, io.SeekStart); err != nil {
+		return fmt.Errorf("seek file failed: %v", err)
+	}
+
 	for ext, sniffer := range snifferRegistry {
-		if sniffer(d.file) {
+		if sniffer(header) {
 			d.audioExt = strings.ToLower(ext)
 			return nil
 		}
@@ -24,20 +35,8 @@ func (d *RawDecoder) Validate() error {
 	return errors.New("audio doesn't recognized")
 }
 
-func (d RawDecoder) Decode() error {
+func (d *RawDecoder) Read(p []byte) (n int, err error) {
-	return nil
+	return d.rd.Read(p)
-}
-
-func (d RawDecoder) GetAudioData() []byte {
-	return d.file
-}
-
-func (d RawDecoder) GetAudioExt() string {
-	return d.audioExt
-}
-
-func (d RawDecoder) GetMeta() Meta {
-	return nil
 }
 
 func init() {

algo/kgm/kgm.go

@@ -1,7 +1,6 @@
 package kgm
 
 import (
-	"bytes"
 	"fmt"
 	"io"
 
@@ -9,64 +8,48 @@ import (
 )
 
 type Decoder struct {
-	header      Header
+	header header
-	initializer kgmCryptoInitializer
+	cipher common.StreamDecoder
 
-	file  []byte
+	rd     io.ReadSeeker
-	audio []byte
+	offset int
 }
 
-type kgmCryptoInitializer func(header *Header, body io.Reader) (io.Reader, error)
+func NewDecoder(rd io.ReadSeeker) common.Decoder {
+	return &Decoder{rd: rd}
+}
 
-var kgmCryptoInitializers = map[uint32]kgmCryptoInitializer{
+var kgmCryptoInitializers = map[uint32]func(header *header) (common.StreamDecoder, error){
 	3: newKgmCryptoV3,
 }
 
-func NewDecoder(file []byte) common.Decoder {
-	return &Decoder{
-		file: file,
-	}
-}
-
-func (d *Decoder) GetAudioData() []byte {
-	return d.audio
-}
-
-func (d *Decoder) GetAudioExt() string {
-	return "" // use sniffer
-}
-
-func (d *Decoder) GetMeta() common.Meta {
-	return nil
-}
-
 func (d *Decoder) Validate() error {
-	if err := d.header.FromBytes(d.file); err != nil {
+	if err := d.header.FromFile(d.rd); err != nil {
 		return err
 	}
 	// TODO; validate crypto version
 
-	var ok bool
+	initializer, ok := kgmCryptoInitializers[d.header.CryptoVersion]
-	d.initializer, ok = kgmCryptoInitializers[d.header.CryptoVersion]
 	if !ok {
 		return fmt.Errorf("kgm: unsupported crypto version %d", d.header.CryptoVersion)
 	}
 
+	var err error
+	d.cipher, err = initializer(&d.header)
+	if err != nil {
+		return fmt.Errorf("kgm: failed to initialize crypto: %w", err)
+	}
+
 	return nil
 }
 
-func (d *Decoder) Decode() error {
+func (d *Decoder) Read(buf []byte) (int, error) {
-	d.audio = d.file[d.header.AudioOffset:]
+	n, err := d.rd.Read(buf)
-
+	if n > 0 {
-	r, err := d.initializer(&d.header, bytes.NewReader(d.audio))
+		d.cipher.Decrypt(buf[:n], d.offset)
-	if err != nil {
+		d.offset += n
-		return fmt.Errorf("kgm: failed to initialize crypto: %w", err)
 	}
-	d.audio, err = io.ReadAll(r)
+	return n, err
-	if err != nil {
-		return fmt.Errorf("kgm: failed to decrypt audio: %w", err)
-	}
-	return nil
 }
 
 func init() {

algo/kgm/kgm_header.go

@@ -21,8 +21,8 @@ var (
 	ErrKgmMagicHeader = errors.New("kgm magic header not matched")
 )
 
-// Header is the header of a KGM file.
+// header is the header of a KGM file.
-type Header struct {
+type header struct {
 	MagicHeader    []byte // 0x00-0x0f: magic header
 	AudioOffset    uint32 // 0x10-0x13: offset of audio data
 	CryptoVersion  uint32 // 0x14-0x17: crypto version
@@ -31,7 +31,7 @@ type Header struct {
 	CryptoKey      []byte // 0x2c-0x3b: crypto key
 }
 
-func (h *Header) FromFile(rd io.ReadSeeker) error {
+func (h *header) FromFile(rd io.ReadSeeker) error {
 	if _, err := rd.Seek(0, io.SeekStart); err != nil {
 		return fmt.Errorf("kgm seek start: %w", err)
 	}
@@ -44,7 +44,7 @@ func (h *Header) FromFile(rd io.ReadSeeker) error {
 	return h.FromBytes(buf)
 }
 
-func (h *Header) FromBytes(buf []byte) error {
+func (h *header) FromBytes(buf []byte) error {
 	if len(buf) < 0x3c {
 		return errors.New("invalid kgm header length")
 	}

algo/kgm/kgm_v3.go

@@ -3,24 +3,22 @@ package kgm
 import (
 	"crypto/md5"
 	"fmt"
-	"io"
+
+	"github.com/unlock-music/cli/algo/common"
 )
 
 // kgmCryptoV3 is kgm file crypto v3
 type kgmCryptoV3 struct {
 	slotBox []byte
 	fileBox []byte
-
-	rd     io.Reader
-	offset int
 }
 
 var kgmV3Slot2Key = map[uint32][]byte{
 	1: {0x6C, 0x2C, 0x2F, 0x27},
 }
 
-func newKgmCryptoV3(header *Header, body io.Reader) (io.Reader, error) {
+func newKgmCryptoV3(header *header) (common.StreamDecoder, error) {
-	c := &kgmCryptoV3{rd: body}
+	c := &kgmCryptoV3{}
 
 	slotKey, ok := kgmV3Slot2Key[header.CryptoSlot]
 	if !ok {
@@ -33,16 +31,7 @@ func newKgmCryptoV3(header *Header, body io.Reader) (io.Reader, error) {
 	return c, nil
 }
 
-func (d *kgmCryptoV3) Read(buf []byte) (int, error) {
+func (d *kgmCryptoV3) Decrypt(b []byte, offset int) {
-	n, err := d.rd.Read(buf)
-	if n > 0 {
-		d.decrypt(buf[:n], d.offset)
-		d.offset += n
-	}
-	return n, err
-}
-
-func (d *kgmCryptoV3) decrypt(b []byte, offset int) {
 	for i := 0; i < len(b); i++ {
 		b[i] ^= d.fileBox[(offset+i)%len(d.fileBox)]
 		b[i] ^= b[i] << 4

algo/kwm/kwm.go

@@ -2,8 +2,9 @@ package kwm
 
 import (
 	"bytes"
-	"encoding/binary"
 	"errors"
+	"fmt"
+	"io"
 	"strconv"
 	"strings"
 	"unicode"
@@ -11,95 +12,63 @@ import (
 	"github.com/unlock-music/cli/algo/common"
 )
 
-var (
+const magicHeader = "yeelion-kuwo-tme"
-	magicHeader = []byte{
-		0x79, 0x65, 0x65, 0x6C, 0x69, 0x6F, 0x6E, 0x2D,
-		0x6B, 0x75, 0x77, 0x6F, 0x2D, 0x74, 0x6D, 0x65}
-	ErrKwFileSize    = errors.New("kwm invalid file size")
-	ErrKwMagicHeader = errors.New("kwm magic header not matched")
-)
-
 const keyPreDefined = "MoOtOiTvINGwd2E6n0E1i7L5t2IoOoNk"
 
 type Decoder struct {
-	file []byte
+	cipher common.StreamDecoder
+
+	rd     io.ReadSeeker
+	offset int
 
-	key       []byte
 	outputExt string
 	bitrate   int
-	mask      []byte
-
-	audio []byte
-}
-
-func (d *Decoder) GetAudioData() []byte {
-	return d.audio
 }
 
 func (d *Decoder) GetAudioExt() string {
 	return "." + d.outputExt
 }
 
-func (d *Decoder) GetMeta() common.Meta {
+func NewDecoder(rd io.ReadSeeker) common.Decoder {
-	return nil
+	return &Decoder{rd: rd}
-}
-
-func NewDecoder(data []byte) common.Decoder {
-	//todo: Notice the input data will be changed for now
-	return &Decoder{file: data}
 }
 
 func (d *Decoder) Validate() error {
-	lenData := len(d.file)
+	header := make([]byte, 0x400) // kwm header is fixed to 1024 bytes
-	if lenData < 1024 {
+	_, err := io.ReadFull(d.rd, header)
-		return ErrKwFileSize
-	}
-	if !bytes.Equal(magicHeader, d.file[:16]) {
-		return ErrKwMagicHeader
-	}
-
-	return nil
-}
-
-func generateMask(key []byte) []byte {
-	keyInt := binary.LittleEndian.Uint64(key)
-	keyStr := strconv.FormatUint(keyInt, 10)
-	keyStrTrim := padOrTruncate(keyStr, 32)
-	mask := make([]byte, 32)
-	for i := 0; i < 32; i++ {
-		mask[i] = keyPreDefined[i] ^ keyStrTrim[i]
-	}
-	return mask
-}
-
-func (d *Decoder) parseBitrateAndType() {
-	bitType := string(bytes.TrimRight(d.file[0x30:0x38], string(byte(0))))
-	charPos := 0
-	for charPos = range bitType {
-		if !unicode.IsNumber(rune(bitType[charPos])) {
-			break
-		}
-	}
-	var err error
-	d.bitrate, err = strconv.Atoi(bitType[:charPos])
 	if err != nil {
-		d.bitrate = 0
+		return fmt.Errorf("kwm read header: %w", err)
 	}
-	d.outputExt = strings.ToLower(bitType[charPos:])
 
+	// check magic header, 0x00 - 0x0F
+	if !bytes.Equal([]byte(magicHeader), header[:len(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 (d *Decoder) Decode() error {
+func parseBitrateAndType(header []byte) (int, string) {
-	d.parseBitrateAndType()
+	tmp := strings.TrimRight(string(header), "\x00")
+	sep := strings.IndexFunc(tmp, func(r rune) bool {
+		return !unicode.IsDigit(r)
+	})
 
-	d.mask = generateMask(d.file[0x18:0x20])
+	bitrate, _ := strconv.Atoi(tmp[:sep]) // just ignore the error
+	outputExt := strings.ToLower(tmp[sep:])
+	return bitrate, outputExt
+}
 
-	d.audio = d.file[1024:]
+func (d *Decoder) Read(b []byte) (int, error) {
-	dataLen := len(d.audio)
+	n, err := d.rd.Read(b)
-	for i := 0; i < dataLen; i++ {
+	if n > 0 {
-		d.audio[i] ^= d.mask[i&0x1F] //equals: [i % 32]
+		d.cipher.Decrypt(b[:n], d.offset)
+		d.offset += n
 	}
-	return nil
+	return n, err
 }
 
 func padOrTruncate(raw string, length int) string {

algo/kwm/kwm_cipher.go

@@ -0,0 +1,31 @@
+package kwm
+
+import (
+	"encoding/binary"
+	"strconv"
+)
+
+type kwmCipher struct {
+	mask []byte
+}
+
+func newKwmCipher(key []byte) *kwmCipher {
+	return &kwmCipher{mask: generateMask(key)}
+}
+
+func generateMask(key []byte) []byte {
+	keyInt := binary.LittleEndian.Uint64(key)
+	keyStr := strconv.FormatUint(keyInt, 10)
+	keyStrTrim := padOrTruncate(keyStr, 32)
+	mask := make([]byte, 32)
+	for i := 0; i < 32; i++ {
+		mask[i] = keyPreDefined[i] ^ keyStrTrim[i]
+	}
+	return mask
+}
+
+func (c kwmCipher) Decrypt(buf []byte, offset int) {
+	for i := range buf {
+		buf[i] ^= c.mask[(offset+i)&0x1F] // equivalent: [i % 32]
+	}
+}

algo/ncm/ncm.go

@@ -16,27 +16,30 @@ import (
 	"github.com/unlock-music/cli/internal/utils"
 )
 
+const magicHeader = "CTENFDAM"
+
 var (
-	magicHeader = []byte{
-		0x43, 0x54, 0x45, 0x4E, 0x46, 0x44, 0x41, 0x4D}
 	keyCore = []byte{
 		0x68, 0x7a, 0x48, 0x52, 0x41, 0x6d, 0x73, 0x6f,
-		0x35, 0x6b, 0x49, 0x6e, 0x62, 0x61, 0x78, 0x57}
+		0x35, 0x6b, 0x49, 0x6e, 0x62, 0x61, 0x78, 0x57,
+	}
 	keyMeta = []byte{
 		0x23, 0x31, 0x34, 0x6C, 0x6A, 0x6B, 0x5F, 0x21,
-		0x5C, 0x5D, 0x26, 0x30, 0x55, 0x3C, 0x27, 0x28}
+		0x5C, 0x5D, 0x26, 0x30, 0x55, 0x3C, 0x27, 0x28,
+	}
 )
 
-func NewDecoder(data []byte) common.Decoder {
+func NewDecoder(rd io.ReadSeeker) common.Decoder {
 	return &Decoder{
-		file:    data,
+		rd: rd,
-		fileLen: uint32(len(data)),
 	}
 }
 
 type Decoder struct {
-	file    []byte
+	rd     io.ReadSeeker
-	fileLen uint32
+	offset int
+
+	cipher common.StreamDecoder
 
 	key []byte
 	box []byte
@@ -47,91 +50,128 @@ type Decoder struct {
 
 	cover []byte
 	audio []byte
-
-	offsetKey   uint32
-	offsetMeta  uint32
-	offsetCover uint32
-	offsetAudio uint32
 }
 
 func (d *Decoder) Validate() error {
-	if !bytes.Equal(magicHeader, d.file[:len(magicHeader)]) {
+	if err := d.validateMagicHeader(); err != nil {
-		return errors.New("ncm magic header not match")
+		return err
 	}
-	d.offsetKey = 8 + 2
+
+	if _, err := d.rd.Seek(2, io.SeekCurrent); err != nil { // 2 bytes gap
+		return fmt.Errorf("ncm seek file: %w", err)
+	}
+
+	keyData, err := d.readKeyData()
+	if err != nil {
+		return err
+	}
+
+	if err := d.readMetaData(); err != nil {
+		return fmt.Errorf("read meta date failed: %w", err)
+	}
+
+	if _, err := d.rd.Seek(5, io.SeekCurrent); err != nil { // 5 bytes gap
+		return fmt.Errorf("ncm seek gap: %w", err)
+	}
+
+	if err := d.readCoverData(); err != nil {
+		return fmt.Errorf("parse ncm cover file failed: %w", err)
+	}
+
+	if err := d.parseMeta(); err != nil {
+		return fmt.Errorf("parse meta failed: %w", err)
+	}
+
+	d.cipher = newNcmCipher(keyData)
 	return nil
 }
 
-func (d *Decoder) readKeyData() error {
+func (d *Decoder) validateMagicHeader() error {
-	if d.offsetKey == 0 || d.offsetKey+4 > d.fileLen {
+	header := make([]byte, len(magicHeader)) // 0x00 - 0x07
-		return errors.New("invalid cover file offset")
+	if _, err := d.rd.Read(header); err != nil {
+		return fmt.Errorf("ncm read magic header: %w", err)
+	}
+
+	if !bytes.Equal([]byte(magicHeader), header) {
+		return errors.New("ncm magic header not match")
+	}
+
+	return nil
+}
+
+func (d *Decoder) readKeyData() ([]byte, error) {
+	bKeyLen := make([]byte, 4) //
+	if _, err := io.ReadFull(d.rd, bKeyLen); err != nil {
+		return nil, fmt.Errorf("ncm read key length: %w", err)
 	}
-	bKeyLen := d.file[d.offsetKey : d.offsetKey+4]
 	iKeyLen := binary.LittleEndian.Uint32(bKeyLen)
-	d.offsetMeta = d.offsetKey + 4 + iKeyLen
 
 	bKeyRaw := make([]byte, iKeyLen)
+	if _, err := io.ReadFull(d.rd, bKeyRaw); err != nil {
+		return nil, fmt.Errorf("ncm read key data: %w", err)
+	}
 	for i := uint32(0); i < iKeyLen; i++ {
-		bKeyRaw[i] = d.file[i+4+d.offsetKey] ^ 0x64
+		bKeyRaw[i] ^= 0x64
 	}
 
-	d.key = utils.PKCS7UnPadding(utils.DecryptAes128Ecb(bKeyRaw, keyCore))[17:]
+	return utils.PKCS7UnPadding(utils.DecryptAES128ECB(bKeyRaw, keyCore))[17:], nil
-	return nil
 }
 
 func (d *Decoder) readMetaData() error {
-	if d.offsetMeta == 0 || d.offsetMeta+4 > d.fileLen {
+	bMetaLen := make([]byte, 4) //
-		return errors.New("invalid meta file offset")
+	if _, err := io.ReadFull(d.rd, bMetaLen); err != nil {
+		return fmt.Errorf("ncm read key length: %w", err)
 	}
-	bMetaLen := d.file[d.offsetMeta : d.offsetMeta+4]
 	iMetaLen := binary.LittleEndian.Uint32(bMetaLen)
-	d.offsetCover = d.offsetMeta + 4 + iMetaLen
+
 	if iMetaLen == 0 {
-		return errors.New("no any meta file found")
+		return nil // no meta data
 	}
 
-	// Why sub 22: Remove "163 key(Don't modify):"
+	bMetaRaw := make([]byte, iMetaLen)
-	bKeyRaw := make([]byte, iMetaLen-22)
+	if _, err := io.ReadFull(d.rd, bMetaRaw); err != nil {
-	for i := uint32(0); i < iMetaLen-22; i++ {
+		return fmt.Errorf("ncm read meta data: %w", err)
-		bKeyRaw[i] = d.file[d.offsetMeta+4+22+i] ^ 0x63
+	}
+	bMetaRaw = bMetaRaw[22:] // skip "163 key(Don't modify):"
+	for i := 0; i < len(bMetaRaw); i++ {
+		bMetaRaw[i] ^= 0x63
 	}
 
-	cipherText, err := base64.StdEncoding.DecodeString(string(bKeyRaw))
+	cipherText, err := base64.StdEncoding.DecodeString(string(bMetaRaw))
 	if err != nil {
 		return errors.New("decode ncm meta failed: " + err.Error())
 	}
-	metaRaw := utils.PKCS7UnPadding(utils.DecryptAes128Ecb(cipherText, keyMeta))
+	metaRaw := utils.PKCS7UnPadding(utils.DecryptAES128ECB(cipherText, keyMeta))
-	sepIdx := bytes.IndexRune(metaRaw, ':')
+	sep := bytes.IndexByte(metaRaw, ':')
-	if sepIdx == -1 {
+	if sep == -1 {
 		return errors.New("invalid ncm meta file")
 	}
 
-	d.metaType = string(metaRaw[:sepIdx])
+	d.metaType = string(metaRaw[:sep])
-	d.metaRaw = metaRaw[sepIdx+1:]
+	d.metaRaw = metaRaw[sep+1:]
+
 	return nil
 }
 
-func (d *Decoder) buildKeyBox() {
+func (d *Decoder) readCoverData() error {
-	box := make([]byte, 256)
+	bCoverCRC := make([]byte, 4)
-	for i := 0; i < 256; i++ {
+	if _, err := io.ReadFull(d.rd, bCoverCRC); err != nil {
-		box[i] = byte(i)
+		return fmt.Errorf("ncm read cover crc: %w", err)
 	}
 
-	keyLen := len(d.key)
+	bCoverLen := make([]byte, 4) //
-	var j byte
+	if _, err := io.ReadFull(d.rd, bCoverLen); err != nil {
-	for i := 0; i < 256; i++ {
+		return fmt.Errorf("ncm read cover length: %w", err)
-		j = box[i] + j + d.key[i%keyLen]
-		box[i], box[j] = box[j], box[i]
 	}
+	iCoverLen := binary.LittleEndian.Uint32(bCoverLen)
 
-	d.box = make([]byte, 256)
+	coverBuf := make([]byte, iCoverLen)
-	var _i byte
+	if _, err := io.ReadFull(d.rd, coverBuf); err != nil {
-	for i := 0; i < 256; i++ {
+		return fmt.Errorf("ncm read cover data: %w", err)
-		_i = byte(i + 1)
-		si := box[_i]
-		sj := box[_i+si]
-		d.box[i] = box[si+sj]
 	}
+	d.cover = coverBuf
+
+	return nil
 }
 
 func (d *Decoder) parseMeta() error {
@@ -147,54 +187,13 @@ func (d *Decoder) parseMeta() error {
 	}
 }
 
-func (d *Decoder) readCoverData() error {
+func (d *Decoder) Read(buf []byte) (int, error) {
-	if d.offsetCover == 0 || d.offsetCover+13 > d.fileLen {
+	n, err := d.rd.Read(buf)
-		return errors.New("invalid cover file offset")
+	if n > 0 {
+		d.cipher.Decrypt(buf[:n], d.offset)
+		d.offset += n
 	}
-
+	return n, err
-	coverLenStart := d.offsetCover + 5 + 4
-	bCoverLen := d.file[coverLenStart : coverLenStart+4]
-
-	iCoverLen := binary.LittleEndian.Uint32(bCoverLen)
-	d.offsetAudio = coverLenStart + 4 + iCoverLen
-	if iCoverLen == 0 {
-		return nil
-	}
-	d.cover = d.file[coverLenStart+4 : coverLenStart+4+iCoverLen]
-	return nil
-}
-
-func (d *Decoder) readAudioData() error {
-	if d.offsetAudio == 0 || d.offsetAudio > d.fileLen {
-		return errors.New("invalid audio offset")
-	}
-	audioRaw := d.file[d.offsetAudio:]
-	audioLen := len(audioRaw)
-	d.audio = make([]byte, audioLen)
-	for i := uint32(0); i < uint32(audioLen); i++ {
-		d.audio[i] = d.box[i&0xff] ^ audioRaw[i]
-	}
-	return nil
-}
-
-func (d *Decoder) Decode() error {
-	if err := d.readKeyData(); err != nil {
-		return fmt.Errorf("read key data failed: %w", err)
-	}
-	d.buildKeyBox()
-
-	if err := d.readMetaData(); err != nil {
-		return fmt.Errorf("read meta date failed: %w", err)
-	}
-	if err := d.parseMeta(); err != nil {
-		return fmt.Errorf("parse meta failed: %w", err)
-	}
-
-	if err := d.readCoverData(); err != nil {
-		return fmt.Errorf("parse ncm cover file failed: %w", err)
-	}
-
-	return d.readAudioData()
 }
 
 func (d *Decoder) GetAudioExt() string {
@@ -206,10 +205,6 @@ func (d *Decoder) GetAudioExt() string {
 	return ""
 }
 
-func (d *Decoder) GetAudioData() []byte {
-	return d.audio
-}
-
 func (d *Decoder) GetCoverImage(ctx context.Context) ([]byte, error) {
 	if d.cover != nil {
 		return d.cover, nil

algo/ncm/ncm_cipher.go

@@ -0,0 +1,42 @@
+package ncm
+
+type ncmCipher struct {
+	key []byte
+	box []byte
+}
+
+func newNcmCipher(key []byte) *ncmCipher {
+	return &ncmCipher{
+		key: key,
+		box: buildKeyBox(key),
+	}
+}
+
+func (c *ncmCipher) Decrypt(buf []byte, offset int) {
+	for i := 0; i < len(buf); i++ {
+		buf[i] ^= c.box[(i+offset)&0xff]
+	}
+}
+
+func buildKeyBox(key []byte) []byte {
+	box := make([]byte, 256)
+	for i := 0; i < 256; i++ {
+		box[i] = byte(i)
+	}
+
+	var j byte
+	for i := 0; i < 256; i++ {
+		j = box[i] + j + key[i%len(key)]
+		box[i], box[j] = box[j], box[i]
+	}
+
+	ret := make([]byte, 256)
+	var _i byte
+	for i := 0; i < 256; i++ {
+		_i = byte(i + 1)
+		si := box[_i]
+		sj := box[_i+si]
+		ret[i] = box[si+sj]
+	}
+	return ret
+}

algo/qmc/cipher.go

@@ -1,5 +0,0 @@
-package qmc
-
-type streamCipher interface {
-	Decrypt(buf []byte, offset int)
-}

algo/qmc/qmc.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/binary"
 	"errors"
+	"fmt"
 	"io"
 	"strconv"
 	"strings"
@@ -12,14 +13,14 @@ import (
 )
 
 type Decoder struct {
-	r       io.ReadSeeker
+	raw      io.ReadSeeker
-	fileExt string
+	audio    io.Reader
+	offset   int
+	audioLen int
 
-	audioLen   int
+	cipher common.StreamDecoder
-	decodedKey []byte
-	cipher     streamCipher
-	offset     int
 
+	decodedKey    []byte
 	rawMetaExtra1 int
 	rawMetaExtra2 int
 }
@@ -27,78 +28,79 @@ type Decoder struct {
 // Read implements io.Reader, offer the decrypted audio data.
 // Validate should call before Read to check if the file is valid.
 func (d *Decoder) Read(p []byte) (int, error) {
-	n := len(p)
+	n, err := d.audio.Read(p)
-	if d.audioLen <= d.offset {
+	if n > 0 {
-		return 0, io.EOF
+		d.cipher.Decrypt(p[:n], d.offset)
-	} else if d.audioLen-d.offset < n {
+		d.offset += n
-		n = d.audioLen - d.offset
 	}
-	m, err := d.r.Read(p[:n])
+	return n, err
-	if m > 0 {
-		d.cipher.Decrypt(p[:m], d.offset)
-		d.offset += m
-	}
-	return m, err
 }
 
-func NewDecoder(r io.ReadSeeker) (*Decoder, error) {
+func NewDecoder(r io.ReadSeeker) common.Decoder {
-	d := &Decoder{r: r}
+	return &Decoder{raw: r}
+}
+
+func (d *Decoder) Validate() error {
+	// search & derive key
 	err := d.searchKey()
 	if err != nil {
-		return nil, err
+		return err
 	}
 
+	// check cipher type and init decode cipher
 	if len(d.decodedKey) > 300 {
 		d.cipher, err = newRC4Cipher(d.decodedKey)
 		if err != nil {
-			return nil, err
+			return err
 		}
 	} else if len(d.decodedKey) != 0 {
 		d.cipher, err = newMapCipher(d.decodedKey)
 		if err != nil {
-			return nil, err
+			return err
 		}
 	} else {
 		d.cipher = newStaticCipher()
 	}
 
-	_, err = d.r.Seek(0, io.SeekStart)
+	// test with first 16 bytes
-	if err != nil {
+	if err := d.validateDecode(); err != nil {
-		return nil, err
-	}
-
-	return d, nil
-}
-
-func (d *Decoder) Validate() error {
-	buf := make([]byte, 16)
-	if _, err := io.ReadFull(d.r, buf); err != nil {
-		return err
-	}
-	_, err := d.r.Seek(0, io.SeekStart)
-	if err != nil {
 		return err
 	}
 
-	d.cipher.Decrypt(buf, 0)
+	// reset position, limit to audio, prepare for Read
-	fileExt, ok := common.SniffAll(buf)
+	if _, err := d.raw.Seek(0, io.SeekStart); err != nil {
-	if !ok {
+		return err
-		return errors.New("detect file type failed")
 	}
-	d.fileExt = fileExt
+	d.audio = io.LimitReader(d.raw, int64(d.audioLen))
+
 	return nil
 }
 
-func (d *Decoder) GetFileExt() string {
+func (d *Decoder) validateDecode() error {
-	return d.fileExt
+	_, err := d.raw.Seek(0, io.SeekStart)
+	if err != nil {
+		return fmt.Errorf("qmc seek to start: %w", err)
+	}
+
+	buf := make([]byte, 16)
+	if _, err := io.ReadFull(d.raw, buf); err != nil {
+		return fmt.Errorf("qmc read header: %w", err)
+	}
+
+	d.cipher.Decrypt(buf, 0)
+	_, ok := common.SniffAll(buf)
+	if !ok {
+		return errors.New("qmc: detect file type failed")
+	}
+	return nil
 }
 
 func (d *Decoder) searchKey() error {
-	fileSizeM4, err := d.r.Seek(-4, io.SeekEnd)
+	fileSizeM4, err := d.raw.Seek(-4, io.SeekEnd)
 	if err != nil {
 		return err
 	}
-	buf, err := io.ReadAll(io.LimitReader(d.r, 4))
+	buf, err := io.ReadAll(io.LimitReader(d.raw, 4))
 	if err != nil {
 		return err
 	}
@@ -118,13 +120,13 @@ func (d *Decoder) searchKey() error {
 }
 
 func (d *Decoder) readRawKey(rawKeyLen int64) error {
-	audioLen, err := d.r.Seek(-(4 + rawKeyLen), io.SeekEnd)
+	audioLen, err := d.raw.Seek(-(4 + rawKeyLen), io.SeekEnd)
 	if err != nil {
 		return err
 	}
 	d.audioLen = int(audioLen)
 
-	rawKeyData, err := io.ReadAll(io.LimitReader(d.r, rawKeyLen))
+	rawKeyData, err := io.ReadAll(io.LimitReader(d.raw, rawKeyLen))
 	if err != nil {
 		return err
 	}
@@ -142,22 +144,22 @@ func (d *Decoder) readRawKey(rawKeyLen int64) error {
 
 func (d *Decoder) readRawMetaQTag() error {
 	// get raw meta data len
-	if _, err := d.r.Seek(-8, io.SeekEnd); err != nil {
+	if _, err := d.raw.Seek(-8, io.SeekEnd); err != nil {
 		return err
 	}
-	buf, err := io.ReadAll(io.LimitReader(d.r, 4))
+	buf, err := io.ReadAll(io.LimitReader(d.raw, 4))
 	if err != nil {
 		return err
 	}
 	rawMetaLen := int64(binary.BigEndian.Uint32(buf))
 
 	// read raw meta data
-	audioLen, err := d.r.Seek(-(8 + rawMetaLen), io.SeekEnd)
+	audioLen, err := d.raw.Seek(-(8 + rawMetaLen), io.SeekEnd)
 	if err != nil {
 		return err
 	}
 	d.audioLen = int(audioLen)
-	rawMetaData, err := io.ReadAll(io.LimitReader(d.r, rawMetaLen))
+	rawMetaData, err := io.ReadAll(io.LimitReader(d.raw, rawMetaLen))
 	if err != nil {
 		return err
 	}
@@ -206,53 +208,6 @@ func init() {
 		"mflac", "mflac0", //QQ Music New Flac
 	}
 	for _, ext := range supportedExts {
-		common.RegisterDecoder(ext, false, newCompactDecoder)
+		common.RegisterDecoder(ext, false, NewDecoder)
 	}
 }
-
-type compactDecoder struct {
-	decoder   *Decoder
-	createErr error
-	buf       *bytes.Buffer
-}
-
-func newCompactDecoder(p []byte) common.Decoder {
-	r := bytes.NewReader(p)
-	d, err := NewDecoder(r)
-	c := compactDecoder{
-		decoder:   d,
-		createErr: err,
-	}
-	return &c
-}
-
-func (c *compactDecoder) Validate() error {
-	if c.createErr != nil {
-		return c.createErr
-	}
-	return c.decoder.Validate()
-}
-
-func (c *compactDecoder) Decode() error {
-	if c.createErr != nil {
-		return c.createErr
-	}
-	c.buf = bytes.NewBuffer(nil)
-	_, err := io.Copy(c.buf, c.decoder)
-	return err
-}
-
-func (c *compactDecoder) GetAudioData() []byte {
-	return c.buf.Bytes()
-}
-
-func (c *compactDecoder) GetAudioExt() string {
-	if c.createErr != nil {
-		return ""
-	}
-	return c.decoder.GetFileExt()
-}
-
-func (c *compactDecoder) GetMeta() common.Meta {
-	return nil
-}

algo/tm/tm.go

@@ -3,6 +3,8 @@ package tm
 import (
 	"bytes"
 	"errors"
+	"fmt"
+	"io"
 
 	"github.com/unlock-music/cli/algo/common"
 )
@@ -11,66 +13,38 @@ 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 {
-	file        []byte
+	raw    io.ReadSeeker
-	audio       []byte
+	offset int
-	headerMatch bool
+	audio  io.Reader
-	audioExt    string
-}
-
-func (d *Decoder) GetAudioData() []byte {
-	return d.audio
-}
-
-func (d *Decoder) GetAudioExt() string {
-	if d.audioExt != "" {
-		return "." + d.audioExt
-	}
-	return ""
-}
-
-func (d *Decoder) GetMeta() common.Meta {
-	return nil
 }
 
 func (d *Decoder) Validate() error {
-	if len(d.file) < 8 {
+	header := make([]byte, 8)
-		return errors.New("invalid file size")
+	if _, err := io.ReadFull(d.raw, header); err != nil {
+		return fmt.Errorf("tm read header: %w", err)
 	}
-	if !bytes.Equal(magicHeader, d.file[:4]) {
+	if !bytes.Equal(magicHeader, header[:len(magicHeader)]) {
-		return errors.New("not a valid tm file")
+		return errors.New("tm: valid magic header")
 	}
-	d.headerMatch = true
+
+	d.audio = io.MultiReader(bytes.NewReader(replaceHeader), d.raw)
 	return nil
 }
 
-func (d *Decoder) Decode() error {
+func (d *Decoder) Read(buf []byte) (int, error) {
-	d.audio = d.file
+	return d.audio.Read(buf)
-	if d.headerMatch {
-		for i := 0; i < 8; i++ {
-			d.audio[i] = replaceHeader[i]
-		}
-		d.audioExt = "m4a"
-	}
-	return nil
 }
 
-//goland:noinspection GoUnusedExportedFunction
+func NewTmDecoder(rd io.ReadSeeker) common.Decoder {
-func NewDecoder(data []byte) common.Decoder {
+	return &Decoder{raw: rd}
-	return &Decoder{file: data}
-}
 
-func DecoderFuncWithExt(ext string) common.NewDecoderFunc {
-	return func(file []byte) common.Decoder {
-		return &Decoder{file: file, audioExt: ext}
-	}
 }
 
 func init() {
 	// QQ Music IOS M4a
-	common.RegisterDecoder("tm2", false, DecoderFuncWithExt("m4a"))
+	common.RegisterDecoder("tm2", false, NewTmDecoder)
-	common.RegisterDecoder("tm6", false, DecoderFuncWithExt("m4a"))
+	common.RegisterDecoder("tm6", false, NewTmDecoder)
 	// QQ Music IOS Mp3
 	common.RegisterDecoder("tm0", false, common.NewRawDecoder)
 	common.RegisterDecoder("tm3", false, common.NewRawDecoder)
-
 }

algo/xm/xm.go

@@ -3,6 +3,8 @@ package xm
 import (
 	"bytes"
 	"errors"
+	"fmt"
+	"io"
 
 	"github.com/unlock-music/cli/algo/common"
 )
@@ -16,22 +18,19 @@ var (
 		" MP3": "mp3",
 		" A4M": "m4a",
 	}
-	ErrFileSize    = errors.New("xm invalid file size")
 	ErrMagicHeader = errors.New("xm magic header not matched")
 )
 
 type Decoder struct {
-	file      []byte
+	rd     io.ReadSeeker
-	headerLen uint32
+	offset int
+
+	cipher    common.StreamDecoder
 	outputExt string
 	mask      byte
 	audio     []byte
 }
 
-func (d *Decoder) GetAudioData() []byte {
-	return d.audio
-}
-
 func (d *Decoder) GetAudioExt() string {
 	if d.outputExt != "" {
 		return "." + d.outputExt
@@ -40,59 +39,53 @@ func (d *Decoder) GetAudioExt() string {
 	return ""
 }
 
-func (d *Decoder) GetMeta() common.Meta {
+func NewDecoder(rd io.ReadSeeker) common.Decoder {
-	return nil
+	return &Decoder{rd: rd}
-}
-
-func NewDecoder(data []byte) common.Decoder {
-	return &Decoder{file: data}
 }
 
 func (d *Decoder) Validate() error {
-	lenData := len(d.file)
+	header := make([]byte, 16) // xm header is fixed to 16 bytes
-	if lenData < 16 {
+
-		return ErrFileSize
+	if _, err := io.ReadFull(d.rd, header); err != nil {
+		return fmt.Errorf("xm read header: %w", err)
 	}
-	if !bytes.Equal(magicHeader, d.file[:4]) ||
+
-		!bytes.Equal(magicHeader2, d.file[8:12]) {
+	// 0x00 - 0x03 and 0x08 - 0x0B: magic header
+	if !bytes.Equal(magicHeader, header[:4]) || !bytes.Equal(magicHeader2, header[8:12]) {
 		return ErrMagicHeader
 	}
 
+	// 0x04 - 0x07: Audio File Type
 	var ok bool
-	d.outputExt, ok = typeMapping[string(d.file[4:8])]
+	d.outputExt, ok = typeMapping[string(header[4:8])]
 	if !ok {
-		return errors.New("detect unknown xm file type: " + string(d.file[4:8]))
+		return fmt.Errorf("xm detect unknown audio type: %s", string(header[4:8]))
 	}
 
-	d.headerLen = uint32(d.file[12]) | uint32(d.file[13])<<8 | uint32(d.file[14])<<16 // LittleEndian Unit24
+	// 0x0C - 0x0E, Encrypt Start At, LittleEndian Unit24
-	if d.headerLen+16 > uint32(lenData) {
+	encStartAt := uint32(header[12]) | uint32(header[13])<<8 | uint32(header[14])<<16
-		return ErrFileSize
+
-	}
+	// 0x0F, XOR Mask
+	d.cipher = newXmCipher(header[15], int(encStartAt))
+
 	return nil
 }
 
-func (d *Decoder) Decode() error {
+func (d *Decoder) Read(p []byte) (int, error) {
-	d.mask = d.file[15]
+	n, err := d.rd.Read(p)
-	d.audio = d.file[16:]
+	if n > 0 {
-	dataLen := uint32(len(d.audio))
+		d.cipher.Decrypt(p[:n], d.offset)
-	for i := d.headerLen; i < dataLen; i++ {
+		d.offset += n
-		d.audio[i] = ^(d.audio[i] - d.mask)
-	}
-	return nil
-}
-
-func DecoderFuncWithExt(ext string) common.NewDecoderFunc {
-	return func(file []byte) common.Decoder {
-		return &Decoder{file: file, outputExt: ext}
 	}
+	return n, err
 }
 
 func init() {
 	// Xiami Wav/M4a/Mp3/Flac
 	common.RegisterDecoder("xm", false, NewDecoder)
 	// Xiami Typed Format
-	common.RegisterDecoder("wav", false, DecoderFuncWithExt("wav"))
+	common.RegisterDecoder("wav", false, NewDecoder)
-	common.RegisterDecoder("mp3", false, DecoderFuncWithExt("mp3"))
+	common.RegisterDecoder("mp3", false, NewDecoder)
-	common.RegisterDecoder("flac", false, DecoderFuncWithExt("flac"))
+	common.RegisterDecoder("flac", false, NewDecoder)
-	common.RegisterDecoder("m4a", false, DecoderFuncWithExt("m4a"))
+	common.RegisterDecoder("m4a", false, NewDecoder)
 }

algo/xm/xm_cipher.go

@@ -0,0 +1,21 @@
+package xm
+
+type xmCipher struct {
+	mask           byte
+	encryptStartAt int
+}
+
+func newXmCipher(mask byte, encryptStartAt int) *xmCipher {
+	return &xmCipher{
+		mask:           mask,
+		encryptStartAt: encryptStartAt,
+	}
+}
+
+func (c *xmCipher) Decrypt(buf []byte, offset int) {
+	for i := 0; i < len(buf); i++ {
+		if offset+i >= c.encryptStartAt {
+			buf[i] ^= c.mask
+		}
+	}
+}

cmd/um/main.go

@@ -1,8 +1,10 @@
 package main
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -153,10 +155,11 @@ func dealDirectory(inputDir string, outputDir string, skipNoop bool, removeSourc
 }
 
 func tryDecFile(inputFile string, outputDir string, allDec []common.NewDecoderFunc, removeSource bool) error {
-	file, err := os.ReadFile(inputFile)
+	file, err := os.Open(inputFile)
 	if err != nil {
 		return err
 	}
+	defer file.Close()
 
 	var dec common.Decoder
 	for _, decFunc := range allDec {
@@ -171,26 +174,32 @@ func tryDecFile(inputFile string, outputDir string, allDec []common.NewDecoderFu
 	if dec == nil {
 		return errors.New("no any decoder can resolve the file")
 	}
-	if err := dec.Decode(); err != nil {
+
-		return errors.New("failed while decoding: " + err.Error())
+	header := bytes.NewBuffer(nil)
+	_, err = io.CopyN(header, dec, 16)
+	if err != nil {
+		return fmt.Errorf("read header failed: %w", err)
 	}
 
-	outData := dec.GetAudioData()
+	outExt := ".mp3"
-	outExt := dec.GetAudioExt()
+	if ext, ok := common.SniffAll(header.Bytes()); ok {
-	if outExt == "" {
+		outExt = ext
-		if ext, ok := common.SniffAll(outData); ok {
-			outExt = ext
-		} else {
-			outExt = ".mp3"
-		}
 	}
 	filenameOnly := strings.TrimSuffix(filepath.Base(inputFile), filepath.Ext(inputFile))
 
 	outPath := filepath.Join(outputDir, filenameOnly+outExt)
-	err = os.WriteFile(outPath, outData, 0644)
+	outFile, err := os.OpenFile(outPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
 	if err != nil {
 		return err
 	}
+	defer outFile.Close()
+
+	if _, err := io.Copy(outFile, header); err != nil {
+		return err
+	}
+	if _, err := io.Copy(outFile, dec); err != nil {
+		return err
+	}
 
 	// if source file need to be removed
 	if removeSource {

internal/utils/crypto.go

@@ -8,7 +8,7 @@ func PKCS7UnPadding(encrypt []byte) []byte {
 	return encrypt[:(length - unPadding)]
 }
 
-func DecryptAes128Ecb(data, key []byte) []byte {
+func DecryptAES128ECB(data, key []byte) []byte {
 	cipher, _ := aes.NewCipher(key)
 	decrypted := make([]byte, len(data))
 	size := 16