Merge pull request 'feat(ximalaya): initial support' (#42) from feat/ximalaya into master

Reviewed-on: https://git.unlock-music.dev/um/cli/pulls/42

algo/ximalaya/x2m_crypto.go

@@ -0,0 +1,34 @@
+package ximalaya
+
+import (
+	_ "embed"
+	"encoding/binary"
+)
+
+const x2mHeaderSize = 1024
+
+var x2mKey = [...]byte{'x', 'm', 'l', 'y'}
+var x2mScrambleTable = [x2mHeaderSize]uint16{}
+
+//go:embed x2m_scramble_table.bin
+var x2mScrambleTableBytes []byte
+
+func init() {
+	if len(x2mScrambleTableBytes) != 2*x2mHeaderSize {
+		panic("invalid x3m scramble table")
+	}
+	for i := range x3mScrambleTable {
+		x3mScrambleTable[i] = binary.LittleEndian.Uint16(x2mScrambleTableBytes[i*2:])
+	}
+}
+
+// decryptX2MHeader decrypts the header of ximalaya .x2m file.
+// make sure input src is 1024(x2mHeaderSize) bytes long.
+func decryptX2MHeader(src []byte) []byte {
+	dst := make([]byte, len(src))
+	for dstIdx := range src {
+		srcIdx := x2mScrambleTable[dstIdx]
+		dst[dstIdx] = src[srcIdx] ^ x2mKey[dstIdx%len(x2mKey)]
+	}
+	return dst
+}

algo/ximalaya/x3m_crypto.go

@@ -0,0 +1,40 @@
+package ximalaya
+
+import (
+	_ "embed"
+	"encoding/binary"
+)
+
+var x3mKey = [...]byte{
+	'3', '9', '8', '9', 'd', '1', '1', '1',
+	'a', 'a', 'd', '5', '6', '1', '3', '9',
+	'4', '0', 'f', '4', 'f', 'c', '4', '4',
+	'b', '6', '3', '9', 'b', '2', '9', '2',
+}
+
+const x3mHeaderSize = 1024
+
+var x3mScrambleTable = [x3mHeaderSize]uint16{}
+
+//go:embed x3m_scramble_table.bin
+var x3mScrambleTableBytes []byte
+
+func init() {
+	if len(x3mScrambleTableBytes) != 2*x3mHeaderSize {
+		panic("invalid x3m scramble table")
+	}
+	for i := range x3mScrambleTable {
+		x3mScrambleTable[i] = binary.LittleEndian.Uint16(x3mScrambleTableBytes[i*2:])
+	}
+}
+
+// decryptX3MHeader decrypts the header of ximalaya .x3m file.
+// make sure input src is 1024 (x3mHeaderSize) bytes long.
+func decryptX3MHeader(src []byte) []byte {
+	dst := make([]byte, len(src))
+	for dstIdx := range src {
+		srcIdx := x3mScrambleTable[dstIdx]
+		dst[dstIdx] = src[srcIdx] ^ x3mKey[dstIdx%len(x3mKey)]
+	}
+	return dst
+}

algo/ximalaya/ximalaya.go

@@ -0,0 +1,56 @@
+package ximalaya
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	"unlock-music.dev/cli/algo/common"
+)
+
+type Decoder struct {
+	rd     io.ReadSeeker
+	offset int
+
+	audio io.Reader
+}
+
+func NewDecoder(rd io.ReadSeeker) common.Decoder {
+	return &Decoder{rd: rd}
+}
+
+func (d *Decoder) Validate() error {
+	encryptedHeader := make([]byte, x2mHeaderSize)
+	if _, err := io.ReadFull(d.rd, encryptedHeader); err != nil {
+		return fmt.Errorf("ximalaya read header: %w", err)
+	}
+
+	{ // try to decode with x2m
+		header := decryptX2MHeader(encryptedHeader)
+		if _, ok := common.SniffAll(header); ok {
+			d.audio = io.MultiReader(bytes.NewReader(header), d.rd)
+			return nil
+		}
+	}
+
+	{ // try to decode with x3m
+		// not read file again, since x2m and x3m have the same header size
+		header := decryptX3MHeader(encryptedHeader)
+		if _, ok := common.SniffAll(header); ok {
+			d.audio = io.MultiReader(bytes.NewReader(header), d.rd)
+			return nil
+		}
+	}
+
+	return fmt.Errorf("ximalaya: unknown format")
+}
+
+func (d *Decoder) Read(p []byte) (n int, err error) {
+	return d.audio.Read(p)
+}
+
+func init() {
+	common.RegisterDecoder("x2m", false, NewDecoder)
+	common.RegisterDecoder("x3m", false, NewDecoder)
+	common.RegisterDecoder("xm", false, NewDecoder)
+}

cmd/um/main.go

@@ -23,6 +23,7 @@ import (
 	_ "unlock-music.dev/cli/algo/qmc"
 	_ "unlock-music.dev/cli/algo/tm"
 	_ "unlock-music.dev/cli/algo/xiami"
+	_ "unlock-music.dev/cli/algo/ximalaya"
 	"unlock-music.dev/cli/internal/logging"
 )